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Early Challenges: Managing Cash Flow

Post Syndicated from Gleb Budman original https://www.backblaze.com/blog/managing-cash-flow/

Cash flow projection charts

This post by Backblaze’s CEO and co-founder Gleb Budman is the eighth in a series about entrepreneurship. You can choose posts in the series from the list below:

  1. How Backblaze got Started: The Problem, The Solution, and the Stuff In-Between
  2. Building a Competitive Moat: Turning Challenges Into Advantages
  3. From Idea to Launch: Getting Your First Customers
  4. How to Get Your First 1,000 Customers
  5. Surviving Your First Year
  6. How to Compete with Giants
  7. The Decision on Transparency
  8. Early Challenges: Managing Cash Flow

Use the Join button above to receive notification of new posts in this series.

Running out of cash is one of the quickest ways for a startup to go out of business. When you are starting a company the question of where to get cash is usually the top priority, but managing cash flow is critical for every stage in the lifecycle of a company. As a primarily bootstrapped but capital-intensive business, managing cash flow at Backblaze was and still is a key element of our success and requires continued focus. Let’s look at what we learned over the years.

Raising Your Initial Funding

When starting a tech business in Silicon Valley, the default assumption is that you will immediately try to raise venture funding. There are certainly many advantages to raising funding — not the least of which is that you don’t need to be cash-flow positive since you have cash in the bank and the expectation is that you will have a “burn rate,” i.e. you’ll be spending more than you make.

Note: While you’re not expected to be cash-flow positive, that doesn’t mean you don’t have to worry about cash. Cash-flow management will determine your burn rate. Whether you can get to cash-flow breakeven or need to raise another round of funding is a direct byproduct of your cash flow management.

Also, raising funding takes time (most successful fundraising cycles take 3-6 months start-to-finish), and time at a startup is in short supply. Constantly trying to raise funding can take away from product development and pursuing growth opportunities. If you’re not successful in raising funding, you then have to either shut down or find an alternate method of funding the business.

Sources of Funding

Depending on the stage of the company, type of company, and other factors, you may have access to different sources of funding. Let’s list a number of them:

Customers

Sales — the best kind of funding. It is non-dilutive, doesn’t have to be paid back, and is a direct metric of the success of your company.

Pre-Sales — some customers may be willing to pay you for a product in beta, a test, or pre-pay for a product they’ll receive when finished. Pre-Sales income also is great because it shares the characteristics of cash from sales, but you get the cash early. It also can be a good sign that the product you’re building fills a market need. We started charging for Backblaze computer backup while it was still in private beta, which allowed us to not only collect cash from customers, but also test the billing experience and users’ real desire for the service.

Services — if you’re a service company and customers are paying you for that, great. You can effectively scale for the number of hours available in a day. As demand grows, you can add more employees to increase the total number of billable hours.

Note: If you’re a product company and customers are paying you to consult, that can provide much needed cash, and could provide feedback toward the right product. However, it can also distract from your core business, send you down a path where you’re building a product for a single customer, and addict you to a path that prevents you from building a scalable business.

Investors

Yourself — you likely are putting your time into the business, and deferring salary in the process. You may also put your own cash into the business either as an investment or a loan.

Angels — angels are ideal as early investors since they are used to investing in businesses with little to no traction. AngelList is a good place to find them, though finding people you’re connected with through someone that knows you well is best.

Crowdfunding — a component of the JOBS Act permitted entrepreneurs to raise money from nearly anyone since May 2016. The SEC imposes limits on both investors and the companies. This article goes into some depth on the options and sites available.

VCs — VCs are ideal for companies that need to raise at least a few million dollars and intend to build a business that will be worth over $1 billion.

Debt

Friends & Family — F&F are often the first people to give you money because they are investing in you. It’s great to have some early supporters, but it also can be risky to take money from people who aren’t used to the risks. The key advice here is to only take money from people who won’t mind losing it. If someone is talking about using their children’s college funds or borrowing from their 401k, say ‘no thank you’ — even if they’re sure they want to loan you money.

Bank Loans — a variety of loan types exist, but most either require the company to have been operational for a couple years, be able to borrow against money the company has or is making, or be able to get a personal guarantee from the founders whereby their own credit is on the line. Fundera provides a good overview of loan options and can help secure some, but most will not be an option for a brand new startup.

Grants

Government — in some areas there is the potential for government grants to facilitate research. The SBIR program facilitates some such grants.

At Backblaze, we used a number of these options:

• Investors/Yourself
We loaned a cumulative total of a couple hundred thousand dollars to the company and invested our time by going without a salary for a year and a half.
• Customers/Pre-Sales
We started selling the Backblaze service while it was still in beta.
• Customers/Sales
We launched v1.0 and kept selling.
• Investors/Angels
After a year and a half, we raised $370k from 11 angels. All of them were either people whom we knew personally or were a strong recommendation from a mutual friend.
• Debt/Loans
After a couple years we were able to get equipment leases whereby the Storage Pods and hard drives were used as collateral to secure the lease on them.
• Investors/VCs
Ater five years we raised $5m from TMT Investments to add to the balance sheet and invest in growth.

The variety and quantity of sources we used is by no means uncommon.

GAAP vs. Cash

Most companies start tracking financials based on cash, and as they scale they switch to GAAP (Generally Accepted Accounting Principles). Cash is easier to track — we got paid $XXXX and spent $YYY — and as often mentioned, is required for the business to stay alive. GAAP has more subtlety and complexity, but provides a clearer picture of how the business is really doing. Backblaze was on a ‘cash’ system for the first few years, then switched to GAAP. For this post, I’m going to focus on things that help cash flow, not GAAP profitability.

Stages of Cash Flow Management

All-spend

In a pure service business (e.g. solo proprietor law firm), you may have no expenses other than your time, so this stage doesn’t exist. However, in a product business there is a period of time where you are building the product and have nothing to sell. You have zero cash coming in, but have cash going out. Your cash-flow is completely negative and you need funds to cover that.

Sales-generating

Starting to see cash come in from customers is thrilling. I initially had our system set up to email me with every $5 payment we received. You’re making sales, but not covering expenses.

Ramen-profitable

But it takes a lot of $5 payments to pay for servers and salaries, so for a while expenses are likely to outstrip sales. Getting to ramen-profitable is a critical stage where sales cover the business expenses and are “paying enough for the founders to eat ramen.” This extends the runway for a business, but is not completely sustainable, since presumably the founders can’t (or won’t) live forever on a subsistence salary.

Business-profitable

This is the ultimate stage whereby the business is truly profitable, including paying everyone market-rate salaries. A business at this stage is self-sustaining. (Of course, market shifts and plenty of other challenges can kill the business, but cash-flow issues alone will not.)

Note, I’m using the word ‘profitable’ here to mean this is still on a cash-basis.

Backblaze was in the all-spend stage for just over a year, during which time we built the service and hadn’t yet made the service available to customers. Backblaze was in the sales-generating stage for nearly another year before the company was barely ramen-profitable where sales were covering the company expenses and paying the founders minimum wage. (I say ‘barely’ since minimum wage in the SF Bay Area is arguably never subsistence.) It took almost three more years before the company was business-profitable, paying everyone including the founders market-rate.

Cash Flow Forecasting

When raising funding it’s helpful to think of milestones reached. You don’t necessarily need enough cash on day one to last for the next 100 years of the company. Some good milestones to consider are how much cash you need to prove there is a market need, prove you can build a product to meet that need, or get to ramen-profitable.

Two things to consider:

1) Unit Economics (COGS)

If your product is 100% software, this may not be relevant. Once software is built it costs effectively nothing to deliver the product to one customer or one million customers. However, in most businesses there is some incremental cost to provide the product. If you’re selling a hardware device, perhaps you sell it for $100 but it costs you $50 to make it. This is called “COGS” (Cost of Goods Sold).

Many products rely on cloud services where the costs scale with growth. That model works great, but it’s still important to understand what the costs are for the cloud service you use per unit of product you sell.

Support is often done by the founders early-on in a business, but that is another real cost to factor in and estimate on a per-user basis. Taking all of the per unit costs combined, you may charge $10/month/user for your service, but if it costs you $7/month/user in cloud services, you’re only netting $3/month/user.

2) Operating Expenses (OpEx)

These are expenses that don’t scale with the number of product units you sell. Typically this includes research & development, sales & marketing, and general & administrative expenses. Presumably there is a certain level of these functions required to build the product, market it, sell it, and run the organization. You can choose to invest or cut back on these, but you’ll still make the same amount per product unit.

Incremental Net Profit Per Unit

If you’ve calculated your COGS and your unit economics are “upside down,” where the amount you charge is less than that it costs you to provide your service, it’s worth thinking hard about how that’s going to change over time. If it will not change, there is no scale that will make the business work. Presuming you do make money on each unit of product you sell — what is sometimes referred to as “Contribution Margin” — consider how many of those product units you need to sell to cover your operating expenses as described above.

Calculating Your Profit

The math on getting to ramen-profitable is simple:

(Number of Product Units Sold x Contribution Margin) - Operating Expenses = Profit

If your operating expenses include subsistence salaries for the founders and profit > $0, you’re ramen-profitable.

Improving Cash Flow

Having access to sources of cash, whether from selling to customers or other methods, is excellent. But needing less cash gives you more choices and allows you to either dilute less, owe less, or invest more.

There are two ways to improve cash flow:

1) Collect More Cash

The best way to collect more cash is to provide more value to your customers and as a result have them pay you more. Additional features/products/services can allow this. However, you can also collect more cash by changing how you charge for your product. If you have a subscription, changing from charging monthly to yearly dramatically improves your cash flow. If you have a product that customers use up, selling a year’s supply instead of selling them one-by-one can help.

2) Spend Less Cash

Reducing COGS is a fantastic way to spend less cash in a scalable way. If you can do this without harming the product or customer experience, you win. There are a myriad of ways to also reduce operating expenses, including taking sub-market salaries, using your home instead of renting office space, staying focused on your core product, etc.

Ultimately, collecting more and spending less cash dramatically simplifies the process of getting to ramen-profitable and later to business-profitable.

Be Careful (Why GAAP Matters)

A word of caution: while running out of cash will put you out of business immediately, overextending yourself will likely put you out of business not much later. GAAP shows how a business is really doing; cash doesn’t. If you only focus on cash, it is possible to commit yourself to both delivering products and repaying loans in the future in an unsustainable fashion. If you’re taking out loans, watch the total balance and monthly payments you’re committing to. If you’re asking customers for pre-payment, make sure you believe you can deliver on what they’ve paid for.

Summary

There are numerous challenges to building a business, and ensuring you have enough cash is amongst the most important. Having the cash to keep going lets you keep working on all of the other challenges. The frameworks above were critical for maintaining Backblaze’s cash flow and cash balance. Hopefully you can take some of the lessons we learned and apply them to your business. Let us know what works for you in the comments below.

The post Early Challenges: Managing Cash Flow appeared first on Backblaze Blog | Cloud Storage & Cloud Backup.

US Govt Brands Torrent, Streaming & Cyberlocker Sites As Notorious Markets

Post Syndicated from Andy original https://torrentfreak.com/us-govt-brands-torrent-streaming-cyberlocker-sites-as-notorious-markets-180115/

In its annual “Out-of-Cycle Review of Notorious Markets” the office of the United States Trade Representative (USTR) has listed a long list of websites said to be involved in online piracy.

The list is compiled with high-level input from various trade groups, including the MPAA and RIAA who both submitted their recommendations (1,2) during early October last year.

With the word “allegedly” used more than two dozen times in the report, the US government notes that its report does not constitute cast-iron proof of illegal activity. However, it urges the countries from where the so-called “notorious markets” operate to take action where they can, while putting owners and facilitators on notice that their activities are under the spotlight.

“A goal of the List is to motivate appropriate action by owners, operators, and service providers in the private sector of these and similar markets, as well as governments, to reduce piracy and counterfeiting,” the report reads.

“USTR highlights the following marketplaces because they exemplify global counterfeiting and piracy concerns and because the scale of infringing activity in these marketplaces can cause significant harm to U.S. intellectual property (IP) owners, consumers, legitimate online platforms, and the economy.”

The report begins with a page titled “Issue Focus: Illicit Streaming Devices”. Unsurprisingly, particularly given their place in dozens of headlines last year, the segment focus on the set-top box phenomenon. The piece doesn’t list any apps or software tools as such but highlights the general position, claiming a cost to the US entertainment industry of $4-5 billion a year.

Torrent Sites

In common with previous years, the USTR goes on to list several of the world’s top torrent sites but due to changes in circumstances, others have been delisted. ExtraTorrent, which shut down May 2017, is one such example.

As the world’s most famous torrent site, The Pirate Bay gets a prominent mention, with the USTR noting that the site is of “symbolic importance as one of the longest-running and most vocal torrent sites. The USTR underlines the site’s resilience by noting its hydra-like form while revealing an apparent secret concerning its hosting arrangements.

“The Pirate Bay has allegedly had more than a dozen domains hosted in various countries around the world, applies a reverse proxy service, and uses a hosting provider in Vietnam to evade further enforcement action,” the USTR notes.

Other torrent sites singled out for criticism include RARBG, which was nominated for the listing by the movie industry. According to the USTR, the site is hosted in Bosnia and Herzegovina and has changed hosting services to prevent shutdowns in recent years.

1337x.to and the meta-search engine Torrentz2 are also given a prime mention, with the USTR noting that they are “two of the most popular torrent sites that allegedly infringe U.S. content industry’s copyrights.” Russia’s RuTracker is also targeted for criticism, with the government noting that it’s now one of the most popular torrent sites in the world.

Streaming & Cyberlockers

While torrent sites are still important, the USTR reserves considerable space in its report for streaming portals and cyberlocker-type services.

4Shared.com, a file-hosting site that has been targeted by dozens of millions of copyright notices, is reportedly no longer able to use major US payment providers. Nevertheless, the British Virgin Islands company still collects significant sums from premium accounts, advertising, and offshore payment processors, USTR notes.

Cyberlocker Rapidgator gets another prominent mention in 2017, with the USTR noting that the Russian-hosted platform generates millions of dollars every year through premium memberships while employing rewards and affiliate schemes.

Due to its increasing popularity as a hosting and streaming operation, Openload.co (Romania) is now a big target for the USTR. “The site is used frequently in combination with add-ons in illicit streaming devices. In November 2017, users visited Openload.co a staggering 270 million times,” the USTR writes.

Owned by a Swiss company and hosted in the Netherlands, the popular site Uploaded is also criticized by the US alongside France’s 1Fichier.com, which allegedly hosts pirate games while being largely unresponsive to takedown notices. Dopefile.pk, a Pakistan-based storage outfit, is also highlighted.

On the video streaming front, it’s perhaps no surprise that the USTR focuses on sites like FMovies (Sweden), GoStream (Vietnam), Movie4K.tv (Russia) and PrimeWire. An organization collectively known as the MovShare group which encompasses Nowvideo.sx, WholeCloud.net, NowDownload.cd, MeWatchSeries.to and WatchSeries.ac, among others, is also listed.

Unauthorized music / research papers

While most of the above are either focused on video or feature it as part of their repertoire, other sites are listed for their attention to music. Convert2MP3.net is named as one of the most popular stream-ripping sites in the world and is highlighted due to the prevalence of YouTube-downloader sites and the 2017 demise of YouTube-MP3.

“Convert2MP3.net does not appear to have permission from YouTube or other sites and does not have permission from right holders for a wide variety of music represented by major U.S. labels,” the USTR notes.

Given the amount of attention the site has received in 2017 as ‘The Pirate Bay of Research’, Libgen.io and Sci-Hub.io (not to mention the endless proxy and mirror sites that facilitate access) are given a detailed mention in this year’s report.

“Together these sites make it possible to download — all without permission and without remunerating authors, publishers or researchers — millions of copyrighted books by commercial publishers and university presses; scientific, technical and medical journal articles; and publications of technological standards,” the USTR writes.

Service providers

But it’s not only sites that are being put under pressure. Following a growing list of nominations in previous years, Swiss service provider Private Layer is again singled out as a rogue player in the market for hosting 1337x.to and Torrentz2.eu, among others.

“While the exact configuration of websites changes from year to year, this is the fourth consecutive year that the List has stressed the significant international trade impact of Private Layer’s hosting services and the allegedly infringing sites it hosts,” the USTR notes.

“Other listed and nominated sites may also be hosted by Private Layer but are using
reverse proxy services to obfuscate the true host from the public and from law enforcement.”

The USTR notes Switzerland’s efforts to close a legal loophole that restricts enforcement and looks forward to a positive outcome when the draft amendment is considered by parliament.

Perhaps a little surprisingly given its recent anti-piracy efforts and overtures to the US, Russia’s leading social network VK.com again gets a place on the new list. The USTR recognizes VK’s efforts but insists that more needs to be done.

Social networking and e-commerce

“In 2016, VK reached licensing agreements with major record companies, took steps to limit third-party applications dedicated to downloading infringing content from the site, and experimented with content recognition technologies,” the USTR writes.

“Despite these positive signals, VK reportedly continues to be a hub of infringing activity and the U.S. motion picture industry reports that they find thousands of infringing files on the site each month.”

Finally, in addition to traditional pirate sites, the US also lists online marketplaces that allegedly fail to meet appropriate standards. Re-added to the list in 2016 after a brief hiatus in 2015, China’s Alibaba is listed again in 2017. The development provoked an angry response from the company.

Describing his company as a “scapegoat”, Alibaba Group President Michael Evans said that his platform had achieved a 25% drop in takedown requests and has even been removing infringing listings before they make it online.

“In light of all this, it’s clear that no matter how much action we take and progress we make, the USTR is not actually interested in seeing tangible results,” Evans said in a statement.

The full list of sites in the Notorious Markets Report 2017 (pdf) can be found below.

– 1fichier.com – (cyberlocker)
– 4shared.com – (cyberlocker)
– convert2mp3.net – (stream-ripper)
– Dhgate.com (e-commerce)
– Dopefile.pl – (cyberlocker)
– Firestorm-servers.com (pirate gaming service)
– Fmovies.is, Fmovies.se, Fmovies.to – (streaming)
– Gostream.is, Gomovies.to, 123movieshd.to (streaming)
– Indiamart.com (e-commerce)
– Kinogo.club, kinogo.co (streaming host, platform)
– Libgen.io, sci-hub.io, libgen.pw, sci-hub.cc, sci-hub.bz, libgen.info, lib.rus.ec, bookfi.org, bookzz.org, booker.org, booksc.org, book4you.org, bookos-z1.org, booksee.org, b-ok.org (research downloads)
– Movshare Group – Nowvideo.sx, wholecloud.net, auroravid.to, bitvid.sx, nowdownload.ch, cloudtime.to, mewatchseries.to, watchseries.ac (streaming)
– Movie4k.tv (streaming)
– MP3VA.com (music)
– Openload.co (cyberlocker / streaming)
– 1337x.to (torrent site)
– Primewire.ag (streaming)
– Torrentz2, Torrentz2.me, Torrentz2.is (torrent site)
– Rarbg.to (torrent site)
– Rebel (domain company)
– Repelis.tv (movie and TV linking)
– RuTracker.org (torrent site)
– Rapidgator.net (cyberlocker)
– Taobao.com (e-commerce)
– The Pirate Bay (torrent site)
– TVPlus, TVBrowser, Kuaikan (streaming apps and addons, China)
– Uploaded.net (cyberlocker)
– VK.com (social networking)

Source: TF, for the latest info on copyright, file-sharing, torrent sites and more. We also have VPN discounts, offers and coupons

[$] Opening up the GnuBee open NAS system

Post Syndicated from corbet original https://lwn.net/Articles/743609/rss

GnuBee is the brand name
for a line of open hardware boards designed to provide
Linux-based network-attached storage. Given the success of the
crowdfunding campaigns for the first two products, the GB-PC1 and
GB-PC2
(which support 2.5 and 3.5 inch drives respectively), there appears to be a
market for these devices. Given that Linux is quite good at attaching
storage to a network, it seems likely they will perform their core function
more than adequately. My initial focus when exploring my GB-PC1 is not the
performance but the openness: just how open is it really? The best analogy
I can come up with is that of a door with rusty hinges: it can be opened,
but doing so requires determination.

NSA Morale

Post Syndicated from Bruce Schneier original https://www.schneier.com/blog/archives/2018/01/nsa_morale.html

The Washington Post is reporting that poor morale at the NSA is causing a significant talent shortage. A November New York Times article said much the same thing.

The articles point to many factors: the recent reorganization, low pay, and the various leaks. I have been saying for a while that the Shadow Brokers leaks have been much more damaging to the NSA — both to morale and operating capabilities — than Edward Snowden. I think it’ll take most of a decade for them to recover.

Combine Transactional and Analytical Data Using Amazon Aurora and Amazon Redshift

Post Syndicated from Re Alvarez-Parmar original https://aws.amazon.com/blogs/big-data/combine-transactional-and-analytical-data-using-amazon-aurora-and-amazon-redshift/

A few months ago, we published a blog post about capturing data changes in an Amazon Aurora database and sending it to Amazon Athena and Amazon QuickSight for fast analysis and visualization. In this post, I want to demonstrate how easy it can be to take the data in Aurora and combine it with data in Amazon Redshift using Amazon Redshift Spectrum.

With Amazon Redshift, you can build petabyte-scale data warehouses that unify data from a variety of internal and external sources. Because Amazon Redshift is optimized for complex queries (often involving multiple joins) across large tables, it can handle large volumes of retail, inventory, and financial data without breaking a sweat.

In this post, we describe how to combine data in Aurora in Amazon Redshift. Here’s an overview of the solution:

  • Use AWS Lambda functions with Amazon Aurora to capture data changes in a table.
  • Save data in an Amazon S3
  • Query data using Amazon Redshift Spectrum.

We use the following services:

Serverless architecture for capturing and analyzing Aurora data changes

Consider a scenario in which an e-commerce web application uses Amazon Aurora for a transactional database layer. The company has a sales table that captures every single sale, along with a few corresponding data items. This information is stored as immutable data in a table. Business users want to monitor the sales data and then analyze and visualize it.

In this example, you take the changes in data in an Aurora database table and save it in Amazon S3. After the data is captured in Amazon S3, you combine it with data in your existing Amazon Redshift cluster for analysis.

By the end of this post, you will understand how to capture data events in an Aurora table and push them out to other AWS services using AWS Lambda.

The following diagram shows the flow of data as it occurs in this tutorial:

The starting point in this architecture is a database insert operation in Amazon Aurora. When the insert statement is executed, a custom trigger calls a Lambda function and forwards the inserted data. Lambda writes the data that it received from Amazon Aurora to a Kinesis data delivery stream. Kinesis Data Firehose writes the data to an Amazon S3 bucket. Once the data is in an Amazon S3 bucket, it is queried in place using Amazon Redshift Spectrum.

Creating an Aurora database

First, create a database by following these steps in the Amazon RDS console:

  1. Sign in to the AWS Management Console, and open the Amazon RDS console.
  2. Choose Launch a DB instance, and choose Next.
  3. For Engine, choose Amazon Aurora.
  4. Choose a DB instance class. This example uses a small, since this is not a production database.
  5. In Multi-AZ deployment, choose No.
  6. Configure DB instance identifier, Master username, and Master password.
  7. Launch the DB instance.

After you create the database, use MySQL Workbench to connect to the database using the CNAME from the console. For information about connecting to an Aurora database, see Connecting to an Amazon Aurora DB Cluster.

The following screenshot shows the MySQL Workbench configuration:

Next, create a table in the database by running the following SQL statement:

Create Table
CREATE TABLE Sales (
InvoiceID int NOT NULL AUTO_INCREMENT,
ItemID int NOT NULL,
Category varchar(255),
Price double(10,2), 
Quantity int not NULL,
OrderDate timestamp,
DestinationState varchar(2),
ShippingType varchar(255),
Referral varchar(255),
PRIMARY KEY (InvoiceID)
)

You can now populate the table with some sample data. To generate sample data in your table, copy and run the following script. Ensure that the highlighted (bold) variables are replaced with appropriate values.

#!/usr/bin/python
import MySQLdb
import random
import datetime

db = MySQLdb.connect(host="AURORA_CNAME",
                     user="DBUSER",
                     passwd="DBPASSWORD",
                     db="DB")

states = ("AL","AK","AZ","AR","CA","CO","CT","DE","FL","GA","HI","ID","IL","IN",
"IA","KS","KY","LA","ME","MD","MA","MI","MN","MS","MO","MT","NE","NV","NH","NJ",
"NM","NY","NC","ND","OH","OK","OR","PA","RI","SC","SD","TN","TX","UT","VT","VA",
"WA","WV","WI","WY")

shipping_types = ("Free", "3-Day", "2-Day")

product_categories = ("Garden", "Kitchen", "Office", "Household")
referrals = ("Other", "Friend/Colleague", "Repeat Customer", "Online Ad")

for i in range(0,10):
    item_id = random.randint(1,100)
    state = states[random.randint(0,len(states)-1)]
    shipping_type = shipping_types[random.randint(0,len(shipping_types)-1)]
    product_category = product_categories[random.randint(0,len(product_categories)-1)]
    quantity = random.randint(1,4)
    referral = referrals[random.randint(0,len(referrals)-1)]
    price = random.randint(1,100)
    order_date = datetime.date(2016,random.randint(1,12),random.randint(1,30)).isoformat()

    data_order = (item_id, product_category, price, quantity, order_date, state,
    shipping_type, referral)

    add_order = ("INSERT INTO Sales "
                   "(ItemID, Category, Price, Quantity, OrderDate, DestinationState, \
                   ShippingType, Referral) "
                   "VALUES (%s, %s, %s, %s, %s, %s, %s, %s)")

    cursor = db.cursor()
    cursor.execute(add_order, data_order)

    db.commit()

cursor.close()
db.close() 

The following screenshot shows how the table appears with the sample data:

Sending data from Amazon Aurora to Amazon S3

There are two methods available to send data from Amazon Aurora to Amazon S3:

  • Using a Lambda function
  • Using SELECT INTO OUTFILE S3

To demonstrate the ease of setting up integration between multiple AWS services, we use a Lambda function to send data to Amazon S3 using Amazon Kinesis Data Firehose.

Alternatively, you can use a SELECT INTO OUTFILE S3 statement to query data from an Amazon Aurora DB cluster and save it directly in text files that are stored in an Amazon S3 bucket. However, with this method, there is a delay between the time that the database transaction occurs and the time that the data is exported to Amazon S3 because the default file size threshold is 6 GB.

Creating a Kinesis data delivery stream

The next step is to create a Kinesis data delivery stream, since it’s a dependency of the Lambda function.

To create a delivery stream:

  1. Open the Kinesis Data Firehose console
  2. Choose Create delivery stream.
  3. For Delivery stream name, type AuroraChangesToS3.
  4. For Source, choose Direct PUT.
  5. For Record transformation, choose Disabled.
  6. For Destination, choose Amazon S3.
  7. In the S3 bucket drop-down list, choose an existing bucket, or create a new one.
  8. Enter a prefix if needed, and choose Next.
  9. For Data compression, choose GZIP.
  10. In IAM role, choose either an existing role that has access to write to Amazon S3, or choose to generate one automatically. Choose Next.
  11. Review all the details on the screen, and choose Create delivery stream when you’re finished.

 

Creating a Lambda function

Now you can create a Lambda function that is called every time there is a change that needs to be tracked in the database table. This Lambda function passes the data to the Kinesis data delivery stream that you created earlier.

To create the Lambda function:

  1. Open the AWS Lambda console.
  2. Ensure that you are in the AWS Region where your Amazon Aurora database is located.
  3. If you have no Lambda functions yet, choose Get started now. Otherwise, choose Create function.
  4. Choose Author from scratch.
  5. Give your function a name and select Python 3.6 for Runtime
  6. Choose and existing or create a new Role, the role would need to have access to call firehose:PutRecord
  7. Choose Next on the trigger selection screen.
  8. Paste the following code in the code window. Change the stream_name variable to the Kinesis data delivery stream that you created in the previous step.
  9. Choose File -> Save in the code editor and then choose Save.
import boto3
import json

firehose = boto3.client('firehose')
stream_name = ‘AuroraChangesToS3’


def Kinesis_publish_message(event, context):
    
    firehose_data = (("%s,%s,%s,%s,%s,%s,%s,%s\n") %(event['ItemID'], 
    event['Category'], event['Price'], event['Quantity'],
    event['OrderDate'], event['DestinationState'], event['ShippingType'], 
    event['Referral']))
    
    firehose_data = {'Data': str(firehose_data)}
    print(firehose_data)
    
    firehose.put_record(DeliveryStreamName=stream_name,
    Record=firehose_data)

Note the Amazon Resource Name (ARN) of this Lambda function.

Giving Aurora permissions to invoke a Lambda function

To give Amazon Aurora permissions to invoke a Lambda function, you must attach an IAM role with appropriate permissions to the cluster. For more information, see Invoking a Lambda Function from an Amazon Aurora DB Cluster.

Once you are finished, the Amazon Aurora database has access to invoke a Lambda function.

Creating a stored procedure and a trigger in Amazon Aurora

Now, go back to MySQL Workbench, and run the following command to create a new stored procedure. When this stored procedure is called, it invokes the Lambda function you created. Change the ARN in the following code to your Lambda function’s ARN.

DROP PROCEDURE IF EXISTS CDC_TO_FIREHOSE;
DELIMITER ;;
CREATE PROCEDURE CDC_TO_FIREHOSE (IN ItemID VARCHAR(255), 
									IN Category varchar(255), 
									IN Price double(10,2),
                                    IN Quantity int(11),
                                    IN OrderDate timestamp,
                                    IN DestinationState varchar(2),
                                    IN ShippingType varchar(255),
                                    IN Referral  varchar(255)) LANGUAGE SQL 
BEGIN
  CALL mysql.lambda_async('arn:aws:lambda:us-east-1:XXXXXXXXXXXXX:function:CDCFromAuroraToKinesis', 
     CONCAT('{ "ItemID" : "', ItemID, 
            '", "Category" : "', Category,
            '", "Price" : "', Price,
            '", "Quantity" : "', Quantity, 
            '", "OrderDate" : "', OrderDate, 
            '", "DestinationState" : "', DestinationState, 
            '", "ShippingType" : "', ShippingType, 
            '", "Referral" : "', Referral, '"}')
     );
END
;;
DELIMITER ;

Create a trigger TR_Sales_CDC on the Sales table. When a new record is inserted, this trigger calls the CDC_TO_FIREHOSE stored procedure.

DROP TRIGGER IF EXISTS TR_Sales_CDC;
 
DELIMITER ;;
CREATE TRIGGER TR_Sales_CDC
  AFTER INSERT ON Sales
  FOR EACH ROW
BEGIN
  SELECT  NEW.ItemID , NEW.Category, New.Price, New.Quantity, New.OrderDate
  , New.DestinationState, New.ShippingType, New.Referral
  INTO @ItemID , @Category, @Price, @Quantity, @OrderDate
  , @DestinationState, @ShippingType, @Referral;
  CALL  CDC_TO_FIREHOSE(@ItemID , @Category, @Price, @Quantity, @OrderDate
  , @DestinationState, @ShippingType, @Referral);
END
;;
DELIMITER ;

If a new row is inserted in the Sales table, the Lambda function that is mentioned in the stored procedure is invoked.

Verify that data is being sent from the Lambda function to Kinesis Data Firehose to Amazon S3 successfully. You might have to insert a few records, depending on the size of your data, before new records appear in Amazon S3. This is due to Kinesis Data Firehose buffering. To learn more about Kinesis Data Firehose buffering, see the “Amazon S3” section in Amazon Kinesis Data Firehose Data Delivery.

Every time a new record is inserted in the sales table, a stored procedure is called, and it updates data in Amazon S3.

Querying data in Amazon Redshift

In this section, you use the data you produced from Amazon Aurora and consume it as-is in Amazon Redshift. In order to allow you to process your data as-is, where it is, while taking advantage of the power and flexibility of Amazon Redshift, you use Amazon Redshift Spectrum. You can use Redshift Spectrum to run complex queries on data stored in Amazon S3, with no need for loading or other data prep.

Just create a data source and issue your queries to your Amazon Redshift cluster as usual. Behind the scenes, Redshift Spectrum scales to thousands of instances on a per-query basis, ensuring that you get fast, consistent performance even as your dataset grows to beyond an exabyte! Being able to query data that is stored in Amazon S3 means that you can scale your compute and your storage independently. You have the full power of the Amazon Redshift query model and all the reporting and business intelligence tools at your disposal. Your queries can reference any combination of data stored in Amazon Redshift tables and in Amazon S3.

Redshift Spectrum supports open, common data types, including CSV/TSV, Apache Parquet, SequenceFile, and RCFile. Files can be compressed using gzip or Snappy, with other data types and compression methods in the works.

First, create an Amazon Redshift cluster. Follow the steps in Launch a Sample Amazon Redshift Cluster.

Next, create an IAM role that has access to Amazon S3 and Athena. By default, Amazon Redshift Spectrum uses the Amazon Athena data catalog. Your cluster needs authorization to access your external data catalog in AWS Glue or Athena and your data files in Amazon S3.

In the demo setup, I attached AmazonS3FullAccess and AmazonAthenaFullAccess. In a production environment, the IAM roles should follow the standard security of granting least privilege. For more information, see IAM Policies for Amazon Redshift Spectrum.

Attach the newly created role to the Amazon Redshift cluster. For more information, see Associate the IAM Role with Your Cluster.

Next, connect to the Amazon Redshift cluster, and create an external schema and database:

create external schema if not exists spectrum_schema
from data catalog 
database 'spectrum_db' 
region 'us-east-1'
IAM_ROLE 'arn:aws:iam::XXXXXXXXXXXX:role/RedshiftSpectrumRole'
create external database if not exists;

Don’t forget to replace the IAM role in the statement.

Then create an external table within the database:

 CREATE EXTERNAL TABLE IF NOT EXISTS spectrum_schema.ecommerce_sales(
  ItemID int,
  Category varchar,
  Price DOUBLE PRECISION,
  Quantity int,
  OrderDate TIMESTAMP,
  DestinationState varchar,
  ShippingType varchar,
  Referral varchar)
ROW FORMAT DELIMITED
      FIELDS TERMINATED BY ','
LINES TERMINATED BY '\n'
LOCATION 's3://{BUCKET_NAME}/CDC/'

Query the table, and it should contain data. This is a fact table.

select top 10 * from spectrum_schema.ecommerce_sales

 

Next, create a dimension table. For this example, we create a date/time dimension table. Create the table:

CREATE TABLE date_dimension (
  d_datekey           integer       not null sortkey,
  d_dayofmonth        integer       not null,
  d_monthnum          integer       not null,
  d_dayofweek                varchar(10)   not null,
  d_prettydate        date       not null,
  d_quarter           integer       not null,
  d_half              integer       not null,
  d_year              integer       not null,
  d_season            varchar(10)   not null,
  d_fiscalyear        integer       not null)
diststyle all;

Populate the table with data:

copy date_dimension from 's3://reparmar-lab/2016dates' 
iam_role 'arn:aws:iam::XXXXXXXXXXXX:role/redshiftspectrum'
DELIMITER ','
dateformat 'auto';

The date dimension table should look like the following:

Querying data in local and external tables using Amazon Redshift

Now that you have the fact and dimension table populated with data, you can combine the two and run analysis. For example, if you want to query the total sales amount by weekday, you can run the following:

select sum(quantity*price) as total_sales, date_dimension.d_season
from spectrum_schema.ecommerce_sales 
join date_dimension on spectrum_schema.ecommerce_sales.orderdate = date_dimension.d_prettydate 
group by date_dimension.d_season

You get the following results:

Similarly, you can replace d_season with d_dayofweek to get sales figures by weekday:

With Amazon Redshift Spectrum, you pay only for the queries you run against the data that you actually scan. We encourage you to use file partitioning, columnar data formats, and data compression to significantly minimize the amount of data scanned in Amazon S3. This is important for data warehousing because it dramatically improves query performance and reduces cost.

Partitioning your data in Amazon S3 by date, time, or any other custom keys enables Amazon Redshift Spectrum to dynamically prune nonrelevant partitions to minimize the amount of data processed. If you store data in a columnar format, such as Parquet, Amazon Redshift Spectrum scans only the columns needed by your query, rather than processing entire rows. Similarly, if you compress your data using one of the supported compression algorithms in Amazon Redshift Spectrum, less data is scanned.

Analyzing and visualizing Amazon Redshift data in Amazon QuickSight

Modify the Amazon Redshift security group to allow an Amazon QuickSight connection. For more information, see Authorizing Connections from Amazon QuickSight to Amazon Redshift Clusters.

After modifying the Amazon Redshift security group, go to Amazon QuickSight. Create a new analysis, and choose Amazon Redshift as the data source.

Enter the database connection details, validate the connection, and create the data source.

Choose the schema to be analyzed. In this case, choose spectrum_schema, and then choose the ecommerce_sales table.

Next, we add a custom field for Total Sales = Price*Quantity. In the drop-down list for the ecommerce_sales table, choose Edit analysis data sets.

On the next screen, choose Edit.

In the data prep screen, choose New Field. Add a new calculated field Total Sales $, which is the product of the Price*Quantity fields. Then choose Create. Save and visualize it.

Next, to visualize total sales figures by month, create a graph with Total Sales on the x-axis and Order Data formatted as month on the y-axis.

After you’ve finished, you can use Amazon QuickSight to add different columns from your Amazon Redshift tables and perform different types of visualizations. You can build operational dashboards that continuously monitor your transactional and analytical data. You can publish these dashboards and share them with others.

Final notes

Amazon QuickSight can also read data in Amazon S3 directly. However, with the method demonstrated in this post, you have the option to manipulate, filter, and combine data from multiple sources or Amazon Redshift tables before visualizing it in Amazon QuickSight.

In this example, we dealt with data being inserted, but triggers can be activated in response to an INSERT, UPDATE, or DELETE trigger.

Keep the following in mind:

  • Be careful when invoking a Lambda function from triggers on tables that experience high write traffic. This would result in a large number of calls to your Lambda function. Although calls to the lambda_async procedure are asynchronous, triggers are synchronous.
  • A statement that results in a large number of trigger activations does not wait for the call to the AWS Lambda function to complete. But it does wait for the triggers to complete before returning control to the client.
  • Similarly, you must account for Amazon Kinesis Data Firehose limits. By default, Kinesis Data Firehose is limited to a maximum of 5,000 records/second. For more information, see Monitoring Amazon Kinesis Data Firehose.

In certain cases, it may be optimal to use AWS Database Migration Service (AWS DMS) to capture data changes in Aurora and use Amazon S3 as a target. For example, AWS DMS might be a good option if you don’t need to transform data from Amazon Aurora. The method used in this post gives you the flexibility to transform data from Aurora using Lambda before sending it to Amazon S3. Additionally, the architecture has the benefits of being serverless, whereas AWS DMS requires an Amazon EC2 instance for replication.

For design considerations while using Redshift Spectrum, see Using Amazon Redshift Spectrum to Query External Data.

If you have questions or suggestions, please comment below.


Additional Reading

If you found this post useful, be sure to check out Capturing Data Changes in Amazon Aurora Using AWS Lambda and 10 Best Practices for Amazon Redshift Spectrum


About the Authors

Re Alvarez-Parmar is a solutions architect for Amazon Web Services. He helps enterprises achieve success through technical guidance and thought leadership. In his spare time, he enjoys spending time with his two kids and exploring outdoors.

 

 

 

More details about mitigations for the CPU Speculative Execution issue (Google Security Blog)

Post Syndicated from jake original https://lwn.net/Articles/743269/rss

One of the main concerns about the mitigations for the Meltdown/Spectre speculative execution bugs has been performance. The Google Security Blog is reporting negligible performance impact on Google systems for two of the mitigations (kernel page-table isolation and Retpoline): “In response to the vulnerabilities that were discovered we developed a novel mitigation called “Retpoline” — a binary modification technique that protects against “branch target injection” attacks. We shared Retpoline with our industry partners and have deployed it on Google’s systems, where we have observed negligible impact on performance.
In addition, we have deployed Kernel Page Table Isolation (KPTI) — a general purpose technique for better protecting sensitive information in memory from other software running on a machine — to the entire fleet of Google Linux production servers that support all of our products, including Search, Gmail, YouTube, and Google Cloud Platform.
There has been speculation that the deployment of KPTI causes significant performance slowdowns. Performance can vary, as the impact of the KPTI mitigations depends on the rate of system calls made by an application. On most of our workloads, including our cloud infrastructure, we see negligible impact on performance.

WebTorrent Desktop Hits a Million Downloads

Post Syndicated from Ernesto original https://torrentfreak.com/webtorrent-desktop-hits-a-million-downloads-180104/

Fifteen years ago BitTorrent conquered the masses. It offered a superior way to share large video files, something that was virtually impossible at the time.

With the shift to online video streaming, BitTorrent has lost prominence in recent years. That’s a shame, since the technology offers many advantages.

This is one of the reasons why Stanford University graduate Feross Aboukhadijeh invented WebTorrent. The technology, which is supported by most modern browsers, allows users to seamlessly stream videos on the web with BitTorrent.

In the few years that it’s been around, several tools and services have been built on WebTorrent, including a dedicated desktop client. The desktop version basically serves as a torrent client that streams torrents almost instantaneously on Windows, Linux, and Mac.

Add in AirPlay, Chromecast and DLNA support and it brings these videos to any network-connected TV as well. Quite a powerful tool, as many people have discovered in recent months.

This week Feross informed TorrentFreak that WebTorrent Desktop had reached the one million download mark. That’s a major milestone for a modest project with no full-time developer. But while users seem to be happy, it’s not perfect yet.

“WebTorrent Desktop is the best torrent app in existence. Yet, the app suffers from performance issues when too many torrents are added or too many peers show up. It’s also missing important power user features like bandwidth throttling,” Feross says.

The same is true for WebTorrent itself, which the desktop version is built on. The software has been on the verge of version 1.0.0 for over two years now but needs some more work to make the final leap. This is why Feross would like to invest more time into the projects, given the right support.

Last month Feross launched a Patreon campaign to crowdfund future development of WebTorrent including the desktop version. There are dozens of open issues and a lot of plans and with proper funding, the developer can free up time to work on these.

“The goal of the campaign is to allow me to spend a few days per week addressing these issues,” Feross says, adding that all software he works on is completely free and always has been.

Feross and cat

Thus far the fundraising campaign is going well. WebTorrent’s developer has received support from dozens of people, totaling $1,730 a month through Patreon alone, and he has signed up the privacy oriented browser Brave and video site PopChest as Platinum backers.

Community-driven funding is a great way to support Open Source projects, Feross believes, and he is encouraging others to try it out as well.

“I’ve been promoting Patreon heavily within my community as a way for open source software developers to get paid for their work,” Feross says.

“The norm in the industry right now is that no one gets paid — it’s all volunteer work, even though we’re generating a lot of value for the world! Patreon is a really promising solution for software people like me.”

People who want to give WebTorrent Desktop a try can download a copy from the official site. More information on the core WebTorrent technology and its implementations is available there was well. And if you like what you see, Feross still needs a bit of help to reach his Patreon goal.

Source: TF, for the latest info on copyright, file-sharing, torrent sites and more. We also have VPN discounts, offers and coupons

Tamper-Detection App for Android

Post Syndicated from Bruce Schneier original https://www.schneier.com/blog/archives/2018/01/tamper-detectio.html

Edward Snowden and Nathan Freitas have created an Android app that detects when it’s being tampered with. The basic idea is to put the app on a second phone and put the app on or near something important, like your laptop. The app can then text you — and also record audio and video — when something happens around it: when it’s moved, when the lighting changes, and so on. This gives you some protection against the “evil maid attack” against laptops.

Micah Lee has a good article about the app, including some caveats about its use and security.

2017’s “Piracy is Dangerous” Rhetoric Was Digital Reefer Madness

Post Syndicated from Andy original https://torrentfreak.com/2017s-piracy-is-dangerous-rhetoric-was-digital-reefer-madness-171230/

On dozens of occasions during the past year, TF has been compelled to cover the latest entertainment industry anti-piracy scare campaigns. We never have a problem doing so since news is to be reported and we’re all adults with our own minds to evaluate what we’re reading.

Unfortunately, many people behind these efforts seem to be under the impression that their target audience is comprised of simpletons, none of whom are blessed with a brain of their own. Frankly it’s insulting but before we go on, let’s get a few things clear.

Copyright infringement – including uploading, downloading, sharing or streaming – is illegal in most countries. That means that copyright holders are empowered under law to do something about those offenses, either through the civil or criminal courts. While unpalatable to some, most people accept that position and understand that should they be caught in the act, there might be some consequences.

With that said, there are copyright holders out there that need to stop treating people like children at best, idiots at worst. At this point in 2017, there’s no adult out there with the ability to pirate that truly believes that obtaining or sharing the latest movies, TV shows and sports is likely to be completely legal.

If you don’t believe me, ask a pirate why he or she is so excited by their fully-loaded Kodi setup. Hint: It’s because they’re getting content for free and they know full well that isn’t what the copyright holder wants. Then ask them if they want the copyright holder to know their name, address and everything they’ve downloaded. There. That’s your answer.

The point is that these people are not dumb. They know what they’re doing and understand that getting caught is something that might possibly happen. They may not understand precisely how and they may consider the risk to be particularly small (they’d be right too) but they know that it’s something best kept fairly quiet when they aren’t shouting about it to anyone who will listen down the pub.

Copyright holders aren’t dumb either. They know only too well that pirates recognize what they’re doing is probably illegal but they’re at a loss as to what to do about it. For reputable content owners, suing is expensive, doesn’t scale, is a public relations nightmare and, moreover, isn’t effective in solving the problem.

So, we now have a concerted effort to convince pirates that piracy is not only bad for their computers but also bad for their lives. It’s a stated industry aim and we’re going to see more of it in 2018.

If pirate sites aren’t infecting people’s computers with malware from God-knows-where, they’re stealing their identities and emptying their bank accounts, the industries warned in 2017. And if somehow people manage to run this gauntlet of terror without damaging their technology or their finances, then they’ll probably have their house burnt down by an exploding set-top box.

Look, the intention is understandable. Entertainment companies need to contain the piracy problem because if they don’t, it only gets worse. Again, there are few people out there who genuinely expect them to do anything different but this current stampede towards blatant scaremongering is disingenuous at best and utterly ridiculous at worst.

And it won’t work.

While piracy can be engaged in as a solo activity, it’s inherently a social phenomenon. That things can be pirated from here and there, in this way and that, is the stuff of conversations between friends and colleagues, in person and via social media. The information is passed around today like VHS and compact cassettes were passed around three decades ago and people really aren’t talking about malware or their houses catching fire.

In the somewhat unlikely event these topics do get raised for more than a minute, they get dealt with in the same way as anything else.

People inquire whether their friends have ever had their bank accounts emptied or houses burnt down, or if they know anyone who has. When the answer comes back as “no” from literally everyone, people are likely to conclude that the stories are being spread by people trying to stop them getting movies, TV shows, and live sports for free. And they would be right.

That’s not to say that these scare stories don’t have at least some basis in fact, they do.

Many pirate sites do have low-tier advertising which can put users at risk. However, it’s nothing that a decent anti-virus program and/or ad blocker can’t handle, which is something everyone should be running when accessing untrusted sites. Also, being cautious about all electronics imported from overseas is something people should be aware of too, despite the tiny risk these devices appear to pose in the scheme of things.

So, what we have here is the modern day equivalent of Reefer Madness, the 1930’s propaganda movie that tried to scare people away from marijuana with tales of car accidents, suicide, attempted rape and murder.

While somewhat more refined, these modern-day cautionary messages over piracy are destined to fall on ears that are far more shrewd and educated than their 20th-century counterparts. Yet they’re all born out of the same desire, to stop people from getting involved in an activity by warning them that it’s dangerous to them, rather than it having a negative effect on someone else – an industry executive, for example.

It’s all designed to appeal to the selfish nature of people, rather than their empathy for others, but that’s a big mistake.

Most people really do want to do the right thing, as the staggering success of Netflix, iTunes, Spotify, and Amazon show. But the ridiculous costs and/or inaccessibility of live sports, latest movies, or packaged TV shows mean that no matter what warnings get thrown out there, some people will still cut corners if they feel they’re being taken advantage of.

Worst still, if they believe the scare stories are completely ridiculous, eventually they’ll also discount the credibility of the messenger. When that happens, what little trust remains will be eroded.

Then, let’s face it, who wants to buy something from people you can’t trust?

Source: TF, for the latest info on copyright, file-sharing, torrent sites and more. We also have VPN discounts, offers and coupons

Sublist3r – Fast Python Subdomain Enumeration Tool

Post Syndicated from Darknet original https://www.darknet.org.uk/2017/12/sublist3r-fast-python-subdomain-enumeration-tool/?utm_source=rss&utm_medium=social&utm_campaign=darknetfeed

Sublist3r – Fast Python Subdomain Enumeration Tool

Sublist3r is a Python-based tool designed to enumerate subdomains of websites using OSINT. It helps penetration testers and bug hunters collect and gather subdomains for the domain they are targeting.

It also integrates with subbrute for subdomain brute-forcing with word lists.

Features of Sublist3r Subdomain Enumeration Tool

It enumerates subdomains using many search engines such as:

  • Google
  • Yahoo
  • Bing
  • Baidu
  • Ask

The tool also enumerates subdomains using:

  • Netcraft
  • Virustotal
  • ThreatCrowd
  • DNSdumpster
  • ReverseDNS

Requirements of Sublist3r Subdomain Search

It currently supports Python 2 and Python 3.

Read the rest of Sublist3r – Fast Python Subdomain Enumeration Tool now! Only available at Darknet.

Instrumenting Web Apps Using AWS X-Ray

Post Syndicated from Bharath Kumar original https://aws.amazon.com/blogs/devops/instrumenting-web-apps-using-aws-x-ray/

This post was written by James Bowman, Software Development Engineer, AWS X-Ray

AWS X-Ray helps developers analyze and debug distributed applications and underlying services in production. You can identify and analyze root-causes of performance issues and errors, understand customer impact, and extract statistical aggregations (such as histograms) for optimization.

In this blog post, I will provide a step-by-step walkthrough for enabling X-Ray tracing in the Go programming language. You can use these steps to add X-Ray tracing to any distributed application.

Revel: A web framework for the Go language

This section will assist you with designing a guestbook application. Skip to “Instrumenting with AWS X-Ray” section below if you already have a Go language application.

Revel is a web framework for the Go language. It facilitates the rapid development of web applications by providing a predefined framework for controllers, views, routes, filters, and more.

To get started with Revel, run revel new github.com/jamesdbowman/guestbook. A project base is then copied to $GOPATH/src/github.com/jamesdbowman/guestbook.

$ tree -L 2
.
├── README.md
├── app
│ ├── controllers
│ ├── init.go
│ ├── routes
│ ├── tmp
│ └── views
├── conf
│ ├── app.conf
│ └── routes
├── messages
│ └── sample.en
├── public
│ ├── css
│ ├── fonts
│ ├── img
│ └── js
└── tests
└── apptest.go

Writing a guestbook application

A basic guestbook application can consist of just two routes: one to sign the guestbook and another to list all entries.
Let’s set up these routes by adding a Book controller, which can be routed to by modifying ./conf/routes.

./app/controllers/book.go:
package controllers

import (
    "math/rand"
    "time"

    "github.com/aws/aws-sdk-go/aws"
    "github.com/aws/aws-sdk-go/aws/endpoints"
    "github.com/aws/aws-sdk-go/aws/session"
    "github.com/aws/aws-sdk-go/service/dynamodb"
    "github.com/aws/aws-sdk-go/service/dynamodb/dynamodbattribute"
    "github.com/revel/revel"
)

const TABLE_NAME = "guestbook"
const SUCCESS = "Success.\n"
const DAY = 86400

var letters = []rune("ABCDEFGHIJKLMNOPQRSTUVWXYZ")

func init() {
    rand.Seed(time.Now().UnixNano())
}

// randString returns a random string of len n, used for DynamoDB Hash key.
func randString(n int) string {
    b := make([]rune, n)
    for i := range b {
        b[i] = letters[rand.Intn(len(letters))]
    }
    return string(b)
}

// Book controls interactions with the guestbook.
type Book struct {
    *revel.Controller
    ddbClient *dynamodb.DynamoDB
}

// Signature represents a user's signature.
type Signature struct {
    Message string
    Epoch   int64
    ID      string
}

// ddb returns the controller's DynamoDB client, instatiating a new client if necessary.
func (c Book) ddb() *dynamodb.DynamoDB {
    if c.ddbClient == nil {
        sess := session.Must(session.NewSession(&aws.Config{
            Region: aws.String(endpoints.UsWest2RegionID),
        }))
        c.ddbClient = dynamodb.New(sess)
    }
    return c.ddbClient
}

// Sign allows users to sign the book.
// The message is to be passed as application/json typed content, listed under the "message" top level key.
func (c Book) Sign() revel.Result {
    var s Signature

    err := c.Params.BindJSON(&s)
    if err != nil {
        return c.RenderError(err)
    }
    now := time.Now()
    s.Epoch = now.Unix()
    s.ID = randString(20)

    item, err := dynamodbattribute.MarshalMap(s)
    if err != nil {
        return c.RenderError(err)
    }

    putItemInput := &dynamodb.PutItemInput{
        TableName: aws.String(TABLE_NAME),
        Item:      item,
    }
    _, err = c.ddb().PutItem(putItemInput)
    if err != nil {
        return c.RenderError(err)
    }

    return c.RenderText(SUCCESS)
}

// List allows users to list all signatures in the book.
func (c Book) List() revel.Result {
    scanInput := &dynamodb.ScanInput{
        TableName: aws.String(TABLE_NAME),
        Limit:     aws.Int64(100),
    }
    res, err := c.ddb().Scan(scanInput)
    if err != nil {
        return c.RenderError(err)
    }

    messages := make([]string, 0)
    for _, v := range res.Items {
        messages = append(messages, *(v["Message"].S))
    }
    return c.RenderJSON(messages)
}

./conf/routes:
POST /sign Book.Sign
GET /list Book.List

Creating the resources and testing

For the purposes of this blog post, the application will be run and tested locally. We will store and retrieve messages from an Amazon DynamoDB table. Use the following AWS CLI command to create the guestbook table:

aws dynamodb create-table --region us-west-2 --table-name "guestbook" --attribute-definitions AttributeName=ID,AttributeType=S AttributeName=Epoch,AttributeType=N --key-schema AttributeName=ID,KeyType=HASH AttributeName=Epoch,KeyType=RANGE --provisioned-throughput ReadCapacityUnits=5,WriteCapacityUnits=5

Now, let’s test our sign and list routes. If everything is working correctly, the following result appears:

$ curl -d '{"message":"Hello from cURL!"}' -H "Content-Type: application/json" http://localhost:9000/book/sign
Success.
$ curl http://localhost:9000/book/list
[
  "Hello from cURL!"
]%

Integrating with AWS X-Ray

Download and run the AWS X-Ray daemon

The AWS SDKs emit trace segments over UDP on port 2000. (This port can be configured.) In order for the trace segments to make it to the X-Ray service, the daemon must listen on this port and batch the segments in calls to the PutTraceSegments API.
For information about downloading and running the X-Ray daemon, see the AWS X-Ray Developer Guide.

Installing the AWS X-Ray SDK for Go

To download the SDK from GitHub, run go get -u github.com/aws/aws-xray-sdk-go/... The SDK will appear in the $GOPATH.

Enabling the incoming request filter

The first step to instrumenting an application with AWS X-Ray is to enable the generation of trace segments on incoming requests. The SDK conveniently provides an implementation of http.Handler which does exactly that. To ensure incoming web requests travel through this handler, we can modify app/init.go, adding a custom function to be run on application start.

import (
    "github.com/aws/aws-xray-sdk-go/xray"
    "github.com/revel/revel"
)

...

func init() {
  ...
    revel.OnAppStart(installXRayHandler)
}

func installXRayHandler() {
    revel.Server.Handler = xray.Handler(xray.NewFixedSegmentNamer("GuestbookApp"), revel.Server.Handler)
}

The application will now emit a segment for each incoming web request. The service graph appears:

You can customize the name of the segment to make it more descriptive by providing an alternate implementation of SegmentNamer to xray.Handler. For example, you can use xray.NewDynamicSegmentNamer(fallback, pattern) in place of the fixed namer. This namer will use the host name from the incoming web request (if it matches pattern) as the segment name. This is often useful when you are trying to separate different instances of the same application.

In addition, HTTP-centric information such as method and URL is collected in the segment’s http subsection:

"http": {
    "request": {
        "url": "/book/list",
        "method": "GET",
        "user_agent": "curl/7.54.0",
        "client_ip": "::1"
    },
    "response": {
        "status": 200
    }
},

Instrumenting outbound calls

To provide detailed performance metrics for distributed applications, the AWS X-Ray SDK needs to measure the time it takes to make outbound requests. Trace context is passed to downstream services using the X-Amzn-Trace-Id header. To draw a detailed and accurate representation of a distributed application, outbound call instrumentation is required.

AWS SDK calls

The AWS X-Ray SDK for Go provides a one-line AWS client wrapper that enables the collection of detailed per-call metrics for any AWS client. We can modify the DynamoDB client instantiation to include this line:

// ddb returns the controller's DynamoDB client, instatiating a new client if necessary.
func (c Book) ddb() *dynamodb.DynamoDB {
    if c.ddbClient == nil {
        sess := session.Must(session.NewSession(&aws.Config{
            Region: aws.String(endpoints.UsWest2RegionID),
        }))
        c.ddbClient = dynamodb.New(sess)
        xray.AWS(c.ddbClient.Client) // add subsegment-generating X-Ray handlers to this client
    }
    return c.ddbClient
}

We also need to ensure that the segment generated by our xray.Handler is passed to these AWS calls so that the X-Ray SDK knows to which segment these generated subsegments belong. In Go, the context.Context object is passed throughout the call path to achieve this goal. (In most other languages, some variant of ThreadLocal is used.) AWS clients provide a *WithContext method variant for each AWS operation, which we need to switch to:

_, err = c.ddb().PutItemWithContext(c.Request.Context(), putItemInput)
    res, err := c.ddb().ScanWithContext(c.Request.Context(), scanInput)

We now see much more detail in the Timeline view of the trace for the sign and list operations:

We can use this detail to help diagnose throttling on our DynamoDB table. In the following screenshot, the purple in the DynamoDB service graph node indicates that our table is underprovisioned. The red in the GuestbookApp node indicates that the application is throwing faults due to this throttling.

HTTP calls

Although the guestbook application does not make any non-AWS outbound HTTP calls in its current state, there is a similar one-liner to wrap HTTP clients that make outbound requests. xray.Client(c *http.Client) wraps an existing http.Client (or nil if you want to use a default HTTP client). For example:

resp, err := ctxhttp.Get(ctx, xray.Client(nil), "https://aws.amazon.com/")

Instrumenting local operations

X-Ray can also assist in measuring the performance of local compute operations. To see this in action, let’s create a custom subsegment inside the randString method:


// randString returns a random string of len n, used for DynamoDB Hash key.
func randString(ctx context.Context, n int) string {
    xray.Capture(ctx, "randString", func(innerCtx context.Context) {
        b := make([]rune, n)
        for i := range b {
            b[i] = letters[rand.Intn(len(letters))]
        }
        s := string(b)
    })
    return s
}

// we'll also need to change the callsite

s.ID = randString(c.Request.Context(), 20)

Summary

By now, you are an expert on how to instrument X-Ray for your Go applications. Instrumenting X-Ray with your applications is an easy way to analyze and debug performance issues and understand customer impact. Please feel free to give any feedback or comments below.

For more information about advanced configuration of the AWS X-Ray SDK for Go, see the AWS X-Ray SDK for Go in the AWS X-Ray Developer Guide and the aws/aws-xray-sdk-go GitHub repository.

For more information about some of the advanced X-Ray features such as histograms, annotations, and filter expressions, see the Analyzing Performance for Amazon Rekognition Apps Written on AWS Lambda Using AWS X-Ray blog post.

The Raspberry Pi Christmas shopping list 2017

Post Syndicated from Alex Bate original https://www.raspberrypi.org/blog/christmas-shopping-list-2017/

Looking for the perfect Christmas gift for a beloved maker in your life? Maybe you’d like to give a relative or friend a taste of the world of coding and Raspberry Pi? Whatever you’re looking for, the Raspberry Pi Christmas shopping list will point you in the right direction.

An ice-skating Raspberry Pi - The Raspberry Pi Christmas Shopping List 2017

For those getting started

Thinking about introducing someone special to the wonders of Raspberry Pi during the holidays? Although you can set up your Pi with peripherals from around your home, such as a mobile phone charger, your PC’s keyboard, and the old mouse dwelling in an office drawer, a starter kit is a nice all-in-one package for the budding coder.



Check out the starter kits from Raspberry Pi Approved Resellers such as Pimoroni, The Pi Hut, ModMyPi, Adafruit, CanaKit…the list is pretty long. Our products page will direct you to your closest reseller, or you can head to element14 to pick up the official Raspberry Pi Starter Kit.



You can also buy the Raspberry Pi Press’s brand-new Raspberry Pi Beginners Book, which includes a Raspberry Pi Zero W, a case, a ready-made SD card, and adapter cables.

Once you’ve presented a lucky person with their first Raspberry Pi, it’s time for them to spread their maker wings and learn some new skills.

MagPi Essentials books - The Raspberry Pi Christmas Shopping List 2017

To help them along, you could pick your favourite from among the Official Projects Book volume 3, The MagPi Essentials guides, and the brand-new third edition of Carrie Anne Philbin’s Adventures in Raspberry Pi. (She is super excited about this new edition!)

And you can always add a link to our free resources on the gift tag.

For the maker in your life

If you’re looking for something for a confident digital maker, you can’t go wrong with adding to their arsenal of electric and electronic bits and bobs that are no doubt cluttering drawers and boxes throughout their house.



Components such as servomotors, displays, and sensors are staples of the maker world. And when it comes to jumper wires, buttons, and LEDs, one can never have enough.



You could also consider getting your person a soldering iron, some helpings hands, or small tools such as a Dremel or screwdriver set.

And to make their life a little less messy, pop it all inside a Really Useful Box…because they’re really useful.



For kit makers

While some people like to dive into making head-first and to build whatever comes to mind, others enjoy working with kits.



The Naturebytes kit allows you to record the animal visitors of your garden with the help of a camera and a motion sensor. Footage of your local badgers, birds, deer, and more will be saved to an SD card, or tweeted or emailed to you if it’s in range of WiFi.

Cortec Tiny 4WD - The Raspberry Pi Christmas Shopping List 2017

Coretec’s Tiny 4WD is a kit for assembling a Pi Zero–powered remote-controlled robot at home. Not only is the robot adorable, building it also a great introduction to motors and wireless control.



Bare Conductive’s Touch Board Pro Kit offers everything you need to create interactive electronics projects using conductive paint.

Pi Hut Arcade Kit - The Raspberry Pi Christmas Shopping List 2017

Finally, why not help your favourite maker create their own gaming arcade using the Arcade Building Kit from The Pi Hut?

For the reader

For those who like to curl up with a good read, or spend too much of their day on public transport, a book or magazine subscription is the perfect treat.

For makers, hackers, and those interested in new technologies, our brand-new HackSpace magazine and the ever popular community magazine The MagPi are ideal. Both are available via a physical or digital subscription, and new subscribers to The MagPi also receive a free Raspberry Pi Zero W plus case.

Cover of CoderDojo Nano Make your own game

Marc Scott Beginner's Guide to Coding Book

You can also check out other publications from the Raspberry Pi family, including CoderDojo’s new CoderDojo Nano: Make Your Own Game, Eben Upton and Gareth Halfacree’s Raspberry Pi User Guide, and Marc Scott’s A Beginner’s Guide to Coding. And have I mentioned Carrie Anne’s Adventures in Raspberry Pi yet?

Stocking fillers for everyone

Looking for something small to keep your loved ones occupied on Christmas morning? Or do you have to buy a Secret Santa gift for the office tech? Here are some wonderful stocking fillers to fill your boots with this season.

Pi Hut 3D Christmas Tree - The Raspberry Pi Christmas Shopping List 2017

The Pi Hut 3D Xmas Tree: available as both a pre-soldered and a DIY version, this gadget will work with any 40-pin Raspberry Pi and allows you to create your own mini light show.



Google AIY Voice kit: build your own home assistant using a Raspberry Pi, the MagPi Essentials guide, and this brand-new kit. “Google, play Mariah Carey again…”



Pimoroni’s Raspberry Pi Zero W Project Kits offer everything you need, including the Pi, to make your own time-lapse cameras, music players, and more.



The official Raspberry Pi Sense HAT, Camera Module, and cases for the Pi 3 and Pi Zero will complete the collection of any Raspberry Pi owner, while also opening up exciting project opportunities.

STEAM gifts that everyone will love

Awesome Astronauts | Building LEGO’s Women of NASA!

LEGO Idea’s bought out this amazing ‘Women of NASA’ set, and I thought it would be fun to build, play and learn from these inspiring women! First up, let’s discover a little more about Sally Ride and Mae Jemison, two AWESOME ASTRONAUTS!

Treat the kids, and big kids, in your life to the newest LEGO Ideas set, the Women of NASA — starring Nancy Grace Roman, Margaret Hamilton, Sally Ride, and Mae Jemison!



Explore the world of wearables with Pimoroni’s sewable, hackable, wearable, adorable Bearables kits.



Add lights and motors to paper creations with the Activating Origami Kit, available from The Pi Hut.




We all loved Hidden Figures, and the STEAM enthusiast you know will do too. The film’s available on DVD, and you can also buy the original book, along with other fascinating non-fiction such as Rebecca Skloot’s The Immortal Life of Henrietta Lacks, Rachel Ignotofsky’s Women in Science, and Sydney Padua’s (mostly true) The Thrilling Adventures of Lovelace and Babbage.

Have we missed anything?

With so many amazing kits, HATs, and books available from members of the Raspberry Pi community, it’s hard to only pick a few. Have you found something splendid for the maker in your life? Maybe you’ve created your own kit that uses the Raspberry Pi? Share your favourites with us in the comments below or via our social media accounts.

The post The Raspberry Pi Christmas shopping list 2017 appeared first on Raspberry Pi.

Object models

Post Syndicated from Eevee original https://eev.ee/blog/2017/11/28/object-models/

Anonymous asks, with dollars:

More about programming languages!

Well then!

I’ve written before about what I think objects are: state and behavior, which in practice mostly means method calls.

I suspect that the popular impression of what objects are, and also how they should work, comes from whatever C++ and Java happen to do. From that point of view, the whole post above is probably nonsense. If the baseline notion of “object” is a rigid definition woven tightly into the design of two massively popular languages, then it doesn’t even make sense to talk about what “object” should mean — it does mean the features of those languages, and cannot possibly mean anything else.

I think that’s a shame! It piles a lot of baggage onto a fairly simple idea. Polymorphism, for example, has nothing to do with objects — it’s an escape hatch for static type systems. Inheritance isn’t the only way to reuse code between objects, but it’s the easiest and fastest one, so it’s what we get. Frankly, it’s much closer to a speed tradeoff than a fundamental part of the concept.

We could do with more experimentation around how objects work, but that’s impossible in the languages most commonly thought of as object-oriented.

Here, then, is a (very) brief run through the inner workings of objects in four very dynamic languages. I don’t think I really appreciated objects until I’d spent some time with Python, and I hope this can help someone else whet their own appetite.

Python 3

Of the four languages I’m going to touch on, Python will look the most familiar to the Java and C++ crowd. For starters, it actually has a class construct.

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class Vector:
    def __init__(self, x, y):
        self.x = x
        self.y = y

    def __neg__(self):
        return Vector(-self.x, -self.y)

    def __div__(self, denom):
        return Vector(self.x / denom, self.y / denom)

    @property
    def magnitude(self):
        return (self.x ** 2 + self.y ** 2) ** 0.5

    def normalized(self):
        return self / self.magnitude

The __init__ method is an initializer, which is like a constructor but named differently (because the object already exists in a usable form by the time the initializer is called). Operator overloading is done by implementing methods with other special __dunder__ names. Properties can be created with @property, where the @ is syntax for applying a wrapper function to a function as it’s defined. You can do inheritance, even multiply:

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class Foo(A, B, C):
    def bar(self, x, y, z):
        # do some stuff
        super().bar(x, y, z)

Cool, a very traditional object model.

Except… for some details.

Some details

For one, Python objects don’t have a fixed layout. Code both inside and outside the class can add or remove whatever attributes they want from whatever object they want. The underlying storage is just a dict, Python’s mapping type. (Or, rather, something like one. Also, it’s possible to change, which will probably be the case for everything I say here.)

If you create some attributes at the class level, you’ll start to get a peek behind the curtains:

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class Foo:
    values = []

    def add_value(self, value):
        self.values.append(value)

a = Foo()
b = Foo()
a.add_value('a')
print(a.values)  # ['a']
b.add_value('b')
print(b.values)  # ['a', 'b']

The [] assigned to values isn’t a default assigned to each object. In fact, the individual objects don’t know about it at all! You can use vars(a) to get at the underlying storage dict, and you won’t see a values entry in there anywhere.

Instead, values lives on the class, which is a value (and thus an object) in its own right. When Python is asked for self.values, it checks to see if self has a values attribute; in this case, it doesn’t, so Python keeps going and asks the class for one.

Python’s object model is secretly prototypical — a class acts as a prototype, as a shared set of fallback values, for its objects.

In fact, this is also how method calls work! They aren’t syntactically special at all, which you can see by separating the attribute lookup from the call.

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print("abc".startswith("a"))  # True
meth = "abc".startswith
print(meth("a"))  # True

Reading obj.method looks for a method attribute; if there isn’t one on obj, Python checks the class. Here, it finds one: it’s a function from the class body.

Ah, but wait! In the code I just showed, meth seems to “know” the object it came from, so it can’t just be a plain function. If you inspect the resulting value, it claims to be a “bound method” or “built-in method” rather than a function, too. Something funny is going on here, and that funny something is the descriptor protocol.

Descriptors

Python allows attributes to implement their own custom behavior when read from or written to. Such an attribute is called a descriptor. I’ve written about them before, but here’s a quick overview.

If Python looks up an attribute, finds it in a class, and the value it gets has a __get__ method… then instead of using that value, Python will use the return value of its __get__ method.

The @property decorator works this way. The magnitude property in my original example was shorthand for doing this:

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class MagnitudeDescriptor:
    def __get__(self, instance, owner):
        if instance is None:
            return self
        return (instance.x ** 2 + instance.y ** 2) ** 0.5

class Vector:
    def __init__(self, x, y):
        self.x = x
        self.y = y

    magnitude = MagnitudeDescriptor()

When you ask for somevec.magnitude, Python checks somevec but doesn’t find magnitude, so it consults the class instead. The class does have a magnitude, and it’s a value with a __get__ method, so Python calls that method and somevec.magnitude evaluates to its return value. (The instance is None check is because __get__ is called even if you get the descriptor directly from the class via Vector.magnitude. A descriptor intended to work on instances can’t do anything useful in that case, so the convention is to return the descriptor itself.)

You can also intercept attempts to write to or delete an attribute, and do absolutely whatever you want instead. But note that, similar to operating overloading in Python, the descriptor must be on a class; you can’t just slap one on an arbitrary object and have it work.

This brings me right around to how “bound methods” actually work. Functions are descriptors! The function type implements __get__, and when a function is retrieved from a class via an instance, that __get__ bundles the function and the instance together into a tiny bound method object. It’s essentially:

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class FunctionType:
    def __get__(self, instance, owner):
        if instance is None:
            return self
        return functools.partial(self, instance)

The self passed as the first argument to methods is not special or magical in any way. It’s built out of a few simple pieces that are also readily accessible to Python code.

Note also that because obj.method() is just an attribute lookup and a call, Python doesn’t actually care whether method is a method on the class or just some callable thing on the object. You won’t get the auto-self behavior if it’s on the object, but otherwise there’s no difference.

More attribute access, and the interesting part

Descriptors are one of several ways to customize attribute access. Classes can implement __getattr__ to intervene when an attribute isn’t found on an object; __setattr__ and __delattr__ to intervene when any attribute is set or deleted; and __getattribute__ to implement unconditional attribute access. (That last one is a fantastic way to create accidental recursion, since any attribute access you do within __getattribute__ will of course call __getattribute__ again.)

Here’s what I really love about Python. It might seem like a magical special case that descriptors only work on classes, but it really isn’t. You could implement exactly the same behavior yourself, in pure Python, using only the things I’ve just told you about. Classes are themselves objects, remember, and they are instances of type, so the reason descriptors only work on classes is that type effectively does this:

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class type:
    def __getattribute__(self, name):
        value = super().__getattribute__(name)
        # like all op overloads, __get__ must be on the type, not the instance
        ty = type(value)
        if hasattr(ty, '__get__'):
            # it's a descriptor!  this is a class access so there is no instance
            return ty.__get__(value, None, self)
        else:
            return value

You can even trivially prove to yourself that this is what’s going on by skipping over types behavior:

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class Descriptor:
    def __get__(self, instance, owner):
        print('called!')

class Foo:
    bar = Descriptor()

Foo.bar  # called!
type.__getattribute__(Foo, 'bar')  # called!
object.__getattribute__(Foo, 'bar')  # ...

And that’s not all! The mysterious super function, used to exhaustively traverse superclass method calls even in the face of diamond inheritance, can also be expressed in pure Python using these primitives. You could write your own superclass calling convention and use it exactly the same way as super.

This is one of the things I really like about Python. Very little of it is truly magical; virtually everything about the object model exists in the types rather than the language, which means virtually everything can be customized in pure Python.

Class creation and metaclasses

A very brief word on all of this stuff, since I could talk forever about Python and I have three other languages to get to.

The class block itself is fairly interesting. It looks like this:

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class Name(*bases, **kwargs):
    # code

I’ve said several times that classes are objects, and in fact the class block is one big pile of syntactic sugar for calling type(...) with some arguments to create a new type object.

The Python documentation has a remarkably detailed description of this process, but the gist is:

  • Python determines the type of the new class — the metaclass — by looking for a metaclass keyword argument. If there isn’t one, Python uses the “lowest” type among the provided base classes. (If you’re not doing anything special, that’ll just be type, since every class inherits from object and object is an instance of type.)

  • Python executes the class body. It gets its own local scope, and any assignments or method definitions go into that scope.

  • Python now calls type(name, bases, attrs, **kwargs). The name is whatever was right after class; the bases are position arguments; and attrs is the class body’s local scope. (This is how methods and other class attributes end up on the class.) The brand new type is then assigned to Name.

Of course, you can mess with most of this. You can implement __prepare__ on a metaclass, for example, to use a custom mapping as storage for the local scope — including any reads, which allows for some interesting shenanigans. The only part you can’t really implement in pure Python is the scoping bit, which has a couple extra rules that make sense for classes. (In particular, functions defined within a class block don’t close over the class body; that would be nonsense.)

Object creation

Finally, there’s what actually happens when you create an object — including a class, which remember is just an invocation of type(...).

Calling Foo(...) is implemented as, well, a call. Any type can implement calls with the __call__ special method, and you’ll find that type itself does so. It looks something like this:

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# oh, a fun wrinkle that's hard to express in pure python: type is a class, so
# it's an instance of itself
class type:
    def __call__(self, *args, **kwargs):
        # remember, here 'self' is a CLASS, an instance of type.
        # __new__ is a true constructor: object.__new__ allocates storage
        # for a new blank object
        instance = self.__new__(self, *args, **kwargs)
        # you can return whatever you want from __new__ (!), and __init__
        # is only called on it if it's of the right type
        if isinstance(instance, self):
            instance.__init__(*args, **kwargs)
        return instance

Again, you can trivially confirm this by asking any type for its __call__ method. Assuming that type doesn’t implement __call__ itself, you’ll get back a bound version of types implementation.

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>>> list.__call__
<method-wrapper '__call__' of type object at 0x7fafb831a400>

You can thus implement __call__ in your own metaclass to completely change how subclasses are created — including skipping the creation altogether, if you like.

And… there’s a bunch of stuff I haven’t even touched on.

The Python philosophy

Python offers something that, on the surface, looks like a “traditional” class/object model. Under the hood, it acts more like a prototypical system, where failed attribute lookups simply defer to a superclass or metaclass.

The language also goes to almost superhuman lengths to expose all of its moving parts. Even the prototypical behavior is an implementation of __getattribute__ somewhere, which you are free to completely replace in your own types. Proxying and delegation are easy.

Also very nice is that these features “bundle” well, by which I mean a library author can do all manner of convoluted hijinks, and a consumer of that library doesn’t have to see any of it or understand how it works. You only need to inherit from a particular class (which has a metaclass), or use some descriptor as a decorator, or even learn any new syntax.

This meshes well with Python culture, which is pretty big on the principle of least surprise. These super-advanced features tend to be tightly confined to single simple features (like “makes a weak attribute“) or cordoned with DSLs (e.g., defining a form/struct/database table with a class body). In particular, I’ve never seen a metaclass in the wild implement its own __call__.

I have mixed feelings about that. It’s probably a good thing overall that the Python world shows such restraint, but I wonder if there are some very interesting possibilities we’re missing out on. I implemented a metaclass __call__ myself, just once, in an entity/component system that strove to minimize fuss when communicating between components. It never saw the light of day, but I enjoyed seeing some new things Python could do with the same relatively simple syntax. I wouldn’t mind seeing, say, an object model based on composition (with no inheritance) built atop Python’s primitives.

Lua

Lua doesn’t have an object model. Instead, it gives you a handful of very small primitives for building your own object model. This is pretty typical of Lua — it’s a very powerful language, but has been carefully constructed to be very small at the same time. I’ve never encountered anything else quite like it, and “but it starts indexing at 1!” really doesn’t do it justice.

The best way to demonstrate how objects work in Lua is to build some from scratch. We need two key features. The first is metatables, which bear a passing resemblance to Python’s metaclasses.

Tables and metatables

The table is Lua’s mapping type and its primary data structure. Keys can be any value other than nil. Lists are implemented as tables whose keys are consecutive integers starting from 1. Nothing terribly surprising. The dot operator is sugar for indexing with a string key.

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local t = { a = 1, b = 2 }
print(t['a'])  -- 1
print(t.b)  -- 2
t.c = 3
print(t['c'])  -- 3

A metatable is a table that can be associated with another value (usually another table) to change its behavior. For example, operator overloading is implemented by assigning a function to a special key in a metatable.

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local t = { a = 1, b = 2 }
--print(t + 0)  -- error: attempt to perform arithmetic on a table value

local mt = {
    __add = function(left, right)
        return 12
    end,
}
setmetatable(t, mt)
print(t + 0)  -- 12

Now, the interesting part: one of the special keys is __index, which is consulted when the base table is indexed by a key it doesn’t contain. Here’s a table that claims every key maps to itself.

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local t = {}
local mt = {
    __index = function(table, key)
        return key
    end,
}
setmetatable(t, mt)
print(t.foo)  -- foo
print(t.bar)  -- bar
print(t[3])  -- 3

__index doesn’t have to be a function, either. It can be yet another table, in which case that table is simply indexed with the key. If the key still doesn’t exist and that table has a metatable with an __index, the process repeats.

With this, it’s easy to have several unrelated tables that act as a single table. Call the base table an object, fill the __index table with functions and call it a class, and you have half of an object system. You can even get prototypical inheritance by chaining __indexes together.

At this point things are a little confusing, since we have at least three tables going on, so here’s a diagram. Keep in mind that Lua doesn’t actually have anything called an “object”, “class”, or “method” — those are just convenient nicknames for a particular structure we might build with Lua’s primitives.

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                    ╔═══════════╗        ...
                    ║ metatable ║         ║
                    ╟───────────╢   ┌─────╨───────────────────────┐
                    ║ __index   ╫───┤ lookup table ("superclass") │
                    ╚═══╦═══════╝   ├─────────────────────────────┤
  ╔═══════════╗         ║           │ some other method           ┼─── function() ... end
  ║ metatable ║         ║           └─────────────────────────────┘
  ╟───────────╢   ┌─────╨──────────────────┐
  ║ __index   ╫───┤ lookup table ("class") │
  ╚═══╦═══════╝   ├────────────────────────┤
      ║           │ some method            ┼─── function() ... end
      ║           └────────────────────────┘
┌─────╨─────────────────┐
│ base table ("object") │
└───────────────────────┘

Note that a metatable is not the same as a class; it defines behavior, not methods. Conversely, if you try to use a class directly as a metatable, it will probably not do much. (This is pretty different from e.g. Python, where operator overloads are just methods with funny names. One nice thing about the Lua approach is that you can keep interface-like functionality separate from methods, and avoid clogging up arbitrary objects’ namespaces. You could even use a dummy table as a key and completely avoid name collisions.)

Anyway, code!

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local class = {
    foo = function(a)
        print("foo got", a)
    end,
}
local mt = { __index = class }
-- setmetatable returns its first argument, so this is nice shorthand
local obj1 = setmetatable({}, mt)
local obj2 = setmetatable({}, mt)
obj1.foo(7)  -- foo got 7
obj2.foo(9)  -- foo got 9

Wait, wait, hang on. Didn’t I call these methods? How do they get at the object? Maybe Lua has a magical this variable?

Methods, sort of

Not quite, but this is where the other key feature comes in: method-call syntax. It’s the lightest touch of sugar, just enough to have method invocation.

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-- note the colon!
a:b(c, d, ...)

-- exactly equivalent to this
-- (except that `a` is only evaluated once)
a.b(a, c, d, ...)

-- which of course is really this
a["b"](a, c, d, ...)

Now we can write methods that actually do something.

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local class = {
    bar = function(self)
        print("our score is", self.score)
    end,
}
local mt = { __index = class }
local obj1 = setmetatable({ score = 13 }, mt)
local obj2 = setmetatable({ score = 25 }, mt)
obj1:bar()  -- our score is 13
obj2:bar()  -- our score is 25

And that’s all you need. Much like Python, methods and data live in the same namespace, and Lua doesn’t care whether obj:method() finds a function on obj or gets one from the metatable’s __index. Unlike Python, the function will be passed self either way, because self comes from the use of : rather than from the lookup behavior.

(Aside: strictly speaking, any Lua value can have a metatable — and if you try to index a non-table, Lua will always consult the metatable’s __index. Strings all have the string library as a metatable, so you can call methods on them: try ("%s %s"):format(1, 2). I don’t think Lua lets user code set the metatable for non-tables, so this isn’t that interesting, but if you’re writing Lua bindings from C then you can wrap your pointers in metatables to give them methods implemented in C.)

Bringing it all together

Of course, writing all this stuff every time is a little tedious and error-prone, so instead you might want to wrap it all up inside a little function. No problem.

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local function make_object(body)
    -- create a metatable
    local mt = { __index = body }
    -- create a base table to serve as the object itself
    local obj = setmetatable({}, mt)
    -- and, done
    return obj
end

-- you can leave off parens if you're only passing in 
local Dog = {
    -- this acts as a "default" value; if obj.barks is missing, __index will
    -- kick in and find this value on the class.  but if obj.barks is assigned
    -- to, it'll go in the object and shadow the value here.
    barks = 0,

    bark = function(self)
        self.barks = self.barks + 1
        print("woof!")
    end,
}

local mydog = make_object(Dog)
mydog:bark()  -- woof!
mydog:bark()  -- woof!
mydog:bark()  -- woof!
print(mydog.barks)  -- 3
print(Dog.barks)  -- 0

It works, but it’s fairly barebones. The nice thing is that you can extend it pretty much however you want. I won’t reproduce an entire serious object system here — lord knows there are enough of them floating around — but the implementation I have for my LÖVE games lets me do this:

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local Animal = Object:extend{
    cries = 0,
}

-- called automatically by Object
function Animal:init()
    print("whoops i couldn't think of anything interesting to put here")
end

-- this is just nice syntax for adding a first argument called 'self', then
-- assigning this function to Animal.cry
function Animal:cry()
    self.cries = self.cries + 1
end

local Cat = Animal:extend{}

function Cat:cry()
    print("meow!")
    Cat.__super.cry(self)
end

local cat = Cat()
cat:cry()  -- meow!
cat:cry()  -- meow!
print(cat.cries)  -- 2

When I say you can extend it however you want, I mean that. I could’ve implemented Python (2)-style super(Cat, self):cry() syntax; I just never got around to it. I could even make it work with multiple inheritance if I really wanted to — or I could go the complete opposite direction and only implement composition. I could implement descriptors, customizing the behavior of individual table keys. I could add pretty decent syntax for composition/proxying. I am trying very hard to end this section now.

The Lua philosophy

Lua’s philosophy is to… not have a philosophy? It gives you the bare minimum to make objects work, and you can do absolutely whatever you want from there. Lua does have something resembling prototypical inheritance, but it’s not so much a first-class feature as an emergent property of some very simple tools. And since you can make __index be a function, you could avoid the prototypical behavior and do something different entirely.

The very severe downside, of course, is that you have to find or build your own object system — which can get pretty confusing very quickly, what with the multiple small moving parts. Third-party code may also have its own object system with subtly different behavior. (Though, in my experience, third-party code tries very hard to avoid needing an object system at all.)

It’s hard to say what the Lua “culture” is like, since Lua is an embedded language that’s often a little different in each environment. I imagine it has a thousand millicultures, instead. I can say that the tedium of building my own object model has led me into something very “traditional”, with prototypical inheritance and whatnot. It’s partly what I’m used to, but it’s also just really dang easy to get working.

Likewise, while I love properties in Python and use them all the dang time, I’ve yet to use a single one in Lua. They wouldn’t be particularly hard to add to my object model, but having to add them myself (or shop around for an object model with them and also port all my code to use it) adds a huge amount of friction. I’ve thought about designing an interesting ECS with custom object behavior, too, but… is it really worth the effort? For all the power and flexibility Lua offers, the cost is that by the time I have something working at all, I’m too exhausted to actually use any of it.

JavaScript

JavaScript is notable for being preposterously heavily used, yet not having a class block.

Well. Okay. Yes. It has one now. It didn’t for a very long time, and even the one it has now is sugar.

Here’s a vector class again:

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class Vector {
    constructor(x, y) {
        this.x = x;
        this.y = y;
    }

    get magnitude() {
        return Math.sqrt(this.x * this.x + this.y * this.y);
    }

    dot(other) {
        return this.x * other.x + this.y * other.y;
    }
}

In “classic” JavaScript, this would be written as:

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function Vector(x, y) {
    this.x = x;
    this.y = y;
}

Object.defineProperty(Vector.prototype, 'magnitude', {
    configurable: true,
    enumerable: true,
    get: function() {
        return Math.sqrt(this.x * this.x + this.y * this.y);
    },
});


Vector.prototype.dot = function(other) {
    return this.x * other.x + this.y * other.y;
};

Hm, yes. I can see why they added class.

The JavaScript model

In JavaScript, a new type is defined in terms of a function, which is its constructor.

Right away we get into trouble here. There is a very big difference between these two invocations, which I actually completely forgot about just now after spending four hours writing about Python and Lua:

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let vec = Vector(3, 4);
let vec = new Vector(3, 4);

The first calls the function Vector. It assigns some properties to this, which here is going to be window, so now you have a global x and y. It then returns nothing, so vec is undefined.

The second calls Vector with this set to a new empty object, then evaluates to that object. The result is what you’d actually expect.

(You can detect this situation with the strange new.target expression, but I have never once remembered to do so.)

From here, we have true, honest-to-god, first-class prototypical inheritance. The word “prototype” is even right there. When you write this:

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vec.dot(vec2)

JavaScript will look for dot on vec and (presumably) not find it. It then consults vecs prototype, an object you can see for yourself by using Object.getPrototypeOf(). Since vec is a Vector, its prototype is Vector.prototype.

I stress that Vector.prototype is not the prototype for Vector. It’s the prototype for instances of Vector.

(I say “instance”, but the true type of vec here is still just object. If you want to find Vector, it’s automatically assigned to the constructor property of its own prototype, so it’s available as vec.constructor.)

Of course, Vector.prototype can itself have a prototype, in which case the process would continue if dot were not found. A common (and, arguably, very bad) way to simulate single inheritance is to set Class.prototype to an instance of a superclass to get the prototype right, then tack on the methods for Class. Nowadays we can do Object.create(Superclass.prototype).

Now that I’ve been through Python and Lua, though, this isn’t particularly surprising. I kinda spoiled it.

I suppose one difference in JavaScript is that you can tack arbitrary attributes directly onto Vector all you like, and they will remain invisible to instances since they aren’t in the prototype chain. This is kind of backwards from Lua, where you can squirrel stuff away in the metatable.

Another difference is that every single object in JavaScript has a bunch of properties already tacked on — the ones in Object.prototype. Every object (and by “object” I mean any mapping) has a prototype, and that prototype defaults to Object.prototype, and it has a bunch of ancient junk like isPrototypeOf.

(Nit: it’s possible to explicitly create an object with no prototype via Object.create(null).)

Like Lua, and unlike Python, JavaScript doesn’t distinguish between keys found on an object and keys found via a prototype. Properties can be defined on prototypes with Object.defineProperty(), but that works just as well directly on an object, too. JavaScript doesn’t have a lot of operator overloading, but some things like Symbol.iterator also work on both objects and prototypes.

About this

You may, at this point, be wondering what this is. Unlike Lua and Python (and the last language below), this is a special built-in value — a context value, invisibly passed for every function call.

It’s determined by where the function came from. If the function was the result of an attribute lookup, then this is set to the object containing that attribute. Otherwise, this is set to the global object, window. (You can also set this to whatever you want via the call method on functions.)

This decision is made lexically, i.e. from the literal source code as written. There are no Python-style bound methods. In other words:

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// this = obj
obj.method()
// this = window
let meth = obj.method
meth()

Also, because this is reassigned on every function call, it cannot be meaningfully closed over, which makes using closures within methods incredibly annoying. The old approach was to assign this to some other regular name like self (which got syntax highlighting since it’s also a built-in name in browsers); then we got Function.bind, which produced a callable thing with a fixed context value, which was kind of nice; and now finally we have arrow functions, which explicitly close over the current this when they’re defined and don’t change it when called. Phew.

Class syntax

I already showed class syntax, and it’s really just one big macro for doing all the prototype stuff The Right Way. It even prevents you from calling the type without new. The underlying model is exactly the same, and you can inspect all the parts.

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class Vector { ... }

console.log(Vector.prototype);  // { dot: ..., magnitude: ..., ... }
let vec = new Vector(3, 4);
console.log(Object.getPrototypeOf(vec));  // same as Vector.prototype

// i don't know why you would subclass vector but let's roll with it
class Vectest extends Vector { ... }

console.log(Vectest.prototype);  // { ... }
console.log(Object.getPrototypeOf(Vectest.prototype))  // same as Vector.prototype

Alas, class syntax has a couple shortcomings. You can’t use the class block to assign arbitrary data to either the type object or the prototype — apparently it was deemed too confusing that mutations would be shared among instances. Which… is… how prototypes work. How Python works. How JavaScript itself, one of the most popular languages of all time, has worked for twenty-two years. Argh.

You can still do whatever assignment you want outside of the class block, of course. It’s just a little ugly, and not something I’d think to look for with a sugary class.

A more subtle result of this behavior is that a class block isn’t quite the same syntax as an object literal. The check for data isn’t a runtime thing; class Foo { x: 3 } fails to parse. So JavaScript now has two largely but not entirely identical styles of key/value block.

Attribute access

Here’s where things start to come apart at the seams, just a little bit.

JavaScript doesn’t really have an attribute protocol. Instead, it has two… extension points, I suppose.

One is Object.defineProperty, seen above. For common cases, there’s also the get syntax inside a property literal, which does the same thing. But unlike Python’s @property, these aren’t wrappers around some simple primitives; they are the primitives. JavaScript is the only language of these four to have “property that runs code on access” as a completely separate first-class concept.

If you want to intercept arbitrary attribute access (and some kinds of operators), there’s a completely different primitive: the Proxy type. It doesn’t let you intercept attribute access or operators; instead, it produces a wrapper object that supports interception and defers to the wrapped object by default.

It’s cool to see composition used in this way, but also, extremely weird. If you want to make your own type that overloads in or calling, you have to return a Proxy that wraps your own type, rather than actually returning your own type. And (unlike the other three languages in this post) you can’t return a different type from a constructor, so you have to throw that away and produce objects only from a factory. And instanceof would be broken, but you can at least fix that with Symbol.hasInstance — which is really operator overloading, implement yet another completely different way.

I know the design here is a result of legacy and speed — if any object could intercept all attribute access, then all attribute access would be slowed down everywhere. Fair enough. It still leaves the surface area of the language a bit… bumpy?

The JavaScript philosophy

It’s a little hard to tell. The original idea of prototypes was interesting, but it was hidden behind some very awkward syntax. Since then, we’ve gotten a bunch of extra features awkwardly bolted on to reflect the wildly varied things the built-in types and DOM API were already doing. We have class syntax, but it’s been explicitly designed to avoid exposing the prototype parts of the model.

I admit I don’t do a lot of heavy JavaScript, so I might just be overlooking it, but I’ve seen virtually no code that makes use of any of the recent advances in object capabilities. Forget about custom iterators or overloading call; I can’t remember seeing any JavaScript in the wild that even uses properties yet. I don’t know if everyone’s waiting for sufficient browser support, nobody knows about them, or nobody cares.

The model has advanced recently, but I suspect JavaScript is still shackled to its legacy of “something about prototypes, I don’t really get it, just copy the other code that’s there” as an object model. Alas! Prototypes are so good. Hopefully class syntax will make it a bit more accessible, as it has in Python.

Perl 5

Perl 5 also doesn’t have an object system and expects you to build your own. But where Lua gives you two simple, powerful tools for building one, Perl 5 feels more like a puzzle with half the pieces missing. Clearly they were going for something, but they only gave you half of it.

In brief, a Perl object is a reference that has been blessed with a package.

I need to explain a few things. Honestly, one of the biggest problems with the original Perl object setup was how many strange corners and unique jargon you had to understand just to get off the ground.

(If you want to try running any of this code, you should stick a use v5.26; as the first line. Perl is very big on backwards compatibility, so you need to opt into breaking changes, and even the mundane say builtin is behind a feature gate.)

References

A reference in Perl is sort of like a pointer, but its main use is very different. See, Perl has the strange property that its data structures try very hard to spill their contents all over the place. Despite having dedicated syntax for arrays — @foo is an array variable, distinct from the single scalar variable $foo — it’s actually impossible to nest arrays.

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my @foo = (1, 2, 3, 4);
my @bar = (@foo, @foo);
# @bar is now a flat list of eight items: 1, 2, 3, 4, 1, 2, 3, 4

The idea, I guess, is that an array is not one thing. It’s not a container, which happens to hold multiple things; it is multiple things. Anywhere that expects a single value, such as an array element, cannot contain an array, because an array fundamentally is not a single value.

And so we have “references”, which are a form of indirection, but also have the nice property that they’re single values. They add containment around arrays, and in general they make working with most of Perl’s primitive types much more sensible. A reference to a variable can be taken with the \ operator, or you can use [ ... ] and { ... } to directly create references to anonymous arrays or hashes.

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my @foo = (1, 2, 3, 4);
my @bar = (\@foo, \@foo);
# @bar is now a nested list of two items: [1, 2, 3, 4], [1, 2, 3, 4]

(Incidentally, this is the sole reason I initially abandoned Perl for Python. Non-trivial software kinda requires nesting a lot of data structures, so you end up with references everywhere, and the syntax for going back and forth between a reference and its contents is tedious and ugly.)

A Perl object must be a reference. Perl doesn’t care what kind of reference — it’s usually a hash reference, since hashes are a convenient place to store arbitrary properties, but it could just as well be a reference to an array, a scalar, or even a sub (i.e. function) or filehandle.

I’m getting a little ahead of myself. First, the other half: blessing and packages.

Packages and blessing

Perl packages are just namespaces. A package looks like this:

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package Foo::Bar;

sub quux {
    say "hi from quux!";
}

# now Foo::Bar::quux() can be called from anywhere

Nothing shocking, right? It’s just a named container. A lot of the details are kind of weird, like how a package exists in some liminal quasi-value space, but the basic idea is a Bag Of Stuff.

The final piece is “blessing,” which is Perl’s funny name for binding a package to a reference. A very basic class might look like this:

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package Vector;

# the name 'new' is convention, not special
sub new {
    # perl argument passing is weird, don't ask
    my ($class, $x, $y) = @_;

    # create the object itself -- here, unusually, an array reference makes sense
    my $self = [ $x, $y ];

    # associate the package with that reference
    # note that $class here is just the regular string, 'Vector'
    bless $self, $class;

    return $self;
}

sub x {
    my ($self) = @_;
    return $self->[0];
}

sub y {
    my ($self) = @_;
    return $self->[1];
}

sub magnitude {
    my ($self) = @_;
    return sqrt($self->x ** 2 + $self->y ** 2);
}

# switch back to the "default" package
package main;

# -> is method call syntax, which passes the invocant as the first argument;
# for a package, that's just the package name
my $vec = Vector->new(3, 4);
say $vec->magnitude;  # 5

A few things of note here. First, $self->[0] has nothing to do with objects; it’s normal syntax for getting the value of a index 0 out of an array reference called $self. (Most classes are based on hashrefs and would use $self->{value} instead.) A blessed reference is still a reference and can be treated like one.

In general, -> is Perl’s dereferencey operator, but its exact behavior depends on what follows. If it’s followed by brackets, then it’ll apply the brackets to the thing in the reference: ->{} to index a hash reference, ->[] to index an array reference, and ->() to call a function reference.

But if -> is followed by an identifier, then it’s a method call. For packages, that means calling a function in the package and passing the package name as the first argument. For objects — blessed references — that means calling a function in the associated package and passing the object as the first argument.

This is a little weird! A blessed reference is a superposition of two things: its normal reference behavior, and some completely orthogonal object behavior. Also, object behavior has no notion of methods vs data; it only knows about methods. Perl lets you omit parentheses in a lot of places, including when calling a method with no arguments, so $vec->magnitude is really $vec->magnitude().

Perl’s blessing bears some similarities to Lua’s metatables, but ultimately Perl is much closer to Ruby’s “message passing” approach than the above three languages’ approaches of “get me something and maybe it’ll be callable”. (But this is no surprise — Ruby is a spiritual successor to Perl 5.)

All of this leads to one little wrinkle: how do you actually expose data? Above, I had to write x and y methods. Am I supposed to do that for every single attribute on my type?

Yes! But don’t worry, there are third-party modules to help with this incredibly fundamental task. Take Class::Accessor::Fast, so named because it’s faster than Class::Accessor:

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package Foo;
use base qw(Class::Accessor::Fast);
__PACKAGE__->mk_accessors(qw(fred wilma barney));

(__PACKAGE__ is the lexical name of the current package; qw(...) is a list literal that splits its contents on whitespace.)

This assumes you’re using a hashref with keys of the same names as the attributes. $obj->fred will return the fred key from your hashref, and $obj->fred(4) will change it to 4.

You also, somewhat bizarrely, have to inherit from Class::Accessor::Fast. Speaking of which,

Inheritance

Inheritance is done by populating the package-global @ISA array with some number of (string) names of parent packages. Most code instead opts to write use base ...;, which does the same thing. Or, more commonly, use parent ...;, which… also… does the same thing.

Every package implicitly inherits from UNIVERSAL, which can be freely modified by Perl code.

A method can call its superclass method with the SUPER:: pseudo-package:

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sub foo {
    my ($self) = @_;
    $self->SUPER::foo;
}

However, this does a depth-first search, which means it almost certainly does the wrong thing when faced with multiple inheritance. For a while the accepted solution involved a third-party module, but Perl eventually grew an alternative you have to opt into: C3, which may be more familiar to you as the order Python uses.

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use mro 'c3';

sub foo {
    my ($self) = @_;
    $self->next::method;
}

Offhand, I’m not actually sure how next::method works, seeing as it was originally implemented in pure Perl code. I suspect it involves peeking at the caller’s stack frame. If so, then this is a very different style of customizability from e.g. Python — the MRO was never intended to be pluggable, and the use of a special pseudo-package means it isn’t really, but someone was determined enough to make it happen anyway.

Operator overloading and whatnot

Operator overloading looks a little weird, though really it’s pretty standard Perl.

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package MyClass;

use overload '+' => \&_add;

sub _add {
    my ($self, $other, $swap) = @_;
    ...
}

use overload here is a pragma, where “pragma” means “regular-ass module that does some wizardry when imported”.

\&_add is how you get a reference to the _add sub so you can pass it to the overload module. If you just said &_add or _add, that would call it.

And that’s it; you just pass a map of operators to functions to this built-in module. No worry about name clashes or pollution, which is pretty nice. You don’t even have to give references to functions that live in the package, if you don’t want them to clog your namespace; you could put them in another package, or even inline them anonymously.

One especially interesting thing is that Perl lets you overload every operator. Perl has a lot of operators. It considers some math builtins like sqrt and trig functions to be operators, or at least operator-y enough that you can overload them. You can also overload the “file text” operators, such as -e $path to test whether a file exists. You can overload conversions, including implicit conversion to a regex. And most fascinating to me, you can overload dereferencing — that is, the thing Perl does when you say $hashref->{key} to get at the underlying hash. So a single object could pretend to be references of multiple different types, including a subref to implement callability. Neat.

Somewhat related: you can overload basic operators (indexing, etc.) on basic types (not references!) with the tie function, which is designed completely differently and looks for methods with fixed names. Go figure.

You can intercept calls to nonexistent methods by implementing a function called AUTOLOAD, within which the $AUTOLOAD global will contain the name of the method being called. Originally this feature was, I think, intended for loading binary components or large libraries on-the-fly only when needed, hence the name. Offhand I’m not sure I ever saw it used the way __getattr__ is used in Python.

Is there a way to intercept all method calls? I don’t think so, but it is Perl, so I must be forgetting something.

Actually no one does this any more

Like a decade ago, a council of elder sages sat down and put together a whole whizbang system that covers all of it: Moose.

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package Vector;
use Moose;

has x => (is => 'rw', isa => 'Int');
has y => (is => 'rw', isa => 'Int');

sub magnitude {
    my ($self) = @_;
    return sqrt($self->x ** 2 + $self->y ** 2);
}

Moose has its own way to do pretty much everything, and it’s all built on the same primitives. Moose also adds metaclasses, somehow, despite that the underlying model doesn’t actually support them? I’m not entirely sure how they managed that, but I do remember doing some class introspection with Moose and it was much nicer than the built-in way.

(If you’re wondering, the built-in way begins with looking at the hash called %Vector::. No, that’s not a typo.)

I really cannot stress enough just how much stuff Moose does, but I don’t want to delve into it here since Moose itself is not actually the language model.

The Perl philosophy

I hope you can see what I meant with what I first said about Perl, now. It has multiple inheritance with an MRO, but uses the wrong one by default. It has extensive operator overloading, which looks nothing like how inheritance works, and also some of it uses a totally different mechanism with special method names instead. It only understands methods, not data, leaving you to figure out accessors by hand.

There’s 70% of an object system here with a clear general design it was gunning for, but none of the pieces really look anything like each other. It’s weird, in a distinctly Perl way.

The result is certainly flexible, at least! It’s especially cool that you can use whatever kind of reference you want for storage, though even as I say that, I acknowledge it’s no different from simply subclassing list or something in Python. It feels different in Perl, but maybe only because it looks so different.

I haven’t written much Perl in a long time, so I don’t know what the community is like any more. Moose was already ubiquitous when I left, which you’d think would let me say “the community mostly focuses on the stuff Moose can do” — but even a decade ago, Moose could already do far more than I had ever seen done by hand in Perl. It’s always made a big deal out of roles (read: interfaces), for instance, despite that I’d never seen anyone care about them in Perl before Moose came along. Maybe their presence in Moose has made them more popular? Who knows.

Also, I wrote Perl seriously, but in the intervening years I’ve only encountered people who only ever used Perl for one-offs. Maybe it’ll come as a surprise to a lot of readers that Perl has an object model at all.

End

Well, that was fun! I hope any of that made sense.

Special mention goes to Rust, which doesn’t have an object model you can fiddle with at runtime, but does do things a little differently.

It’s been really interesting thinking about how tiny differences make a huge impact on what people do in practice. Take the choice of storage in Perl versus Python. Perl’s massively common URI class uses a string as the storage, nothing else; I haven’t seen anything like that in Python aside from markupsafe, which is specifically designed as a string type. I would guess this is partly because Perl makes you choose — using a hashref is an obvious default, but you have to make that choice one way or the other. In Python (especially 3), inheriting from object and getting dict-based storage is the obvious thing to do; the ability to use another type isn’t quite so obvious, and doing it “right” involves a tiny bit of extra work.

Or, consider that Lua could have descriptors, but the extra bit of work (especially design work) has been enough of an impediment that I’ve never implemented them. I don’t think the object implementations I’ve looked at have included them, either. Super weird!

In that light, it’s only natural that objects would be so strongly associated with the features Java and C++ attach to them. I think that makes it all the more important to play around! Look at what Moose has done. No, really, you should bear in mind my description of how Perl does stuff and flip through the Moose documentation. It’s amazing what they’ve built.

Pip: digital creation in your pocket from Curious Chip

Post Syndicated from Alex Bate original https://www.raspberrypi.org/blog/pip-curious-chip/

Get your hands on Pip, the handheld Raspberry Pi–based device for aspiring young coders and hackers from Curious Chip.

A GIF of Pip - Curious Chip - Pip handheld device - Raspberry Pi

Pip is a handheld gaming console from Curios Chip which you can now back on Kickstarter. Using the Raspberry Pi Compute Module 3, Pip allows users to code, hack, and play wherever they are.

We created Pip so that anyone can tinker with technology. From beginners to those who know more — Pip makes it easy, simple, and fun!

For gaming

Pip’s smart design may well remind you of a certain handheld gaming console released earlier this year. With its central screen and detachable side controllers, Pip has a size and shape ideal for gaming.

A GIF of Pip - Curious Chip - Pip handheld device - Raspberry Pi

Those who have used a Raspberry Pi with the Raspbian OS might be familiar with Minecraft Pi, a variant of the popular Minecraft game created specifically for Pi users to play and hack for free. Users of Pip will be able to access Minecraft Pi from the portable device and take their block-shaped creations with them wherever they go.

And if that’s not enough, Pip’s Pi brain allows coders to create their own games using Scratch, in addition to giving access a growing library of games in Curious Chip’s online arcade.

Digital making

Pip’s GPIO pins are easily accessible, so that you can expand upon your digital making skills with physical computing projects. Grab your Pip and a handful of jumper leads, and you will be able to connect and control components such as lights, buttons, servomotors, and more!

A smiling girl with Pip and a laptop

You can also attach any of the range of HAT add-on boards available on the market, such as our own Sense HAT, or ones created by Pimoroni, Adafruit, and others. And if you’re looking to learn a new coding language, you’re in luck: Pip supports Python, HTML/CSS, JavaScript, Lua, and PHP.

Maker Pack and add-ons

Backers can also pledge their funds for additional hardware, such as the Maker Pack, an integrated camera, or a Pip Breadboard Kit.

PipHAT and Breadboard add-ons - Curious Chip - Pip handheld device - Raspberry Pi

The breadboard and the optional PipHAT are also compatible with any Raspberry Pi 2 and 3. Nice!

Curiosity from Curious Chip

Users of Pip can program their device via Curiosity, a tool designed specifically for this handheld device.

Pip’s programming tool is called Curiosity, and it’s hosted on Pip itself and accessed via WiFi from any modern web browser, so there’s no software to download and install. Curiosity allows Pip to be programmed using a number of popular programming languages, including JavaScript, Python, Lua, PHP, and HTML5. Scratch-inspired drag-and-drop block programming is also supported with our own Google Blockly–based editor, making it really easy to access all of Pip’s built-in functionality from a simple, visual programming language.

Back the project

If you’d like to back Curious Chip and bag your own Pip, you can check out their Kickstarter page here. And if you watch their promo video closely, you may see a familiar face from the Raspberry Pi community.

Are you planning on starting your own Raspberry Pi-inspired crowd-funded campaign? Then be sure to tag us on social media. We love to see what the community is creating for our little green (or sometimes blue) computer.

The post Pip: digital creation in your pocket from Curious Chip appeared first on Raspberry Pi.

Physical computing blocks at Maker Faire New York

Post Syndicated from Matt Richardson original https://www.raspberrypi.org/blog/physical-computing-blocks/

At events like Maker Faire New York, we love offering visitors the chance to try out easy, inviting, and hands-on activities, so we teamed up with maker Ben Light to create interactive physical computing blocks.

Raspberry Blocks FINAL

In response to the need for hands-on, easy and inviting activities at events such as Maker Faire New York, we teamed up with maker Ben Light to create our interactive physical computing blocks.

Getting hands-on experience at events

At the Raspberry Pi Foundation, we often have the opportunity to engage with families and young people at events such as Maker Faires and STEAM festivals. When we set up a booth, it’s really important to us that we provide an educational, fun experience for everyone who visits us. But there are a few reasons why this can be a challenge.

Girls use the physical computing blocks at Maker Faire New York

For one, you have a broad audience of people with differing levels of experience with computers. Moreover, some people want to take the time to learn a lot, others just want to try something quick and move on. And on top of that, the environment is often loud, crowded, and chaotic…in a good way!

Creating our physical computing blocks

We were up against these challenges when we set out to create a new physical computing experience for our World Maker Faire New York booth. Our goal was to give people the opportunity to try a little bit of circuit making and a little bit of coding — and they should be able to get hands-on with the activity right away.




Inspired by Exploratorium’s Tinkering Studio, we sketched out physical computing blocks which let visitors use the Raspberry Pi’s GPIO pins without needing to work with tiny components or needing to understand how a breadboard works. We turned the sketches over to our friend Ben Light in New York City, and he brought the project to life.

Father and infant child clip crocodile leads to the Raspberry Pi physical computing blocks at Maker Faire New York

As you can see, the activity turned out really well, so we hope to bring it to more events in the future. Thank you, Ben Light, for collaborating with us on it!

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Pirate-Friendly Coinhive’s DNS Hacked, User Hashes Stolen

Post Syndicated from Andy original https://torrentfreak.com/pirate-friendly-coinhives-dns-hacked-user-hashes-stolen-171025/

Just over a month ago, a Javascript cryptocurrency miner was silently added to The Pirate Bay. Noticed by users who observed their CPU usage going through the roof, it later transpired the site was trialing a miner operated by Coinhive.

Many users were disappointed that The Pirate Bay had added the Javascript-based Monero coin miner without their permission. However, it didn’t take long for people to see the potential benefits, with a raft of other sites adding the miner in the hope of generating additional revenue.

Now, however, Coinhive has an unexpected and potentially serious problem to deal with. The company has just revealed that on Monday night its DNS records maintained at Cloudflare were accessed by a third-party, allowing an unnamed attacker to redirect user mining traffic to a server they controlled.

“The DNS records for coinhive.com have been manipulated to redirect requests for the coinhive.min.js to a third party server. This third party server hosted a modified version of the JavaScript file with a hardcoded site key. This essentially let the attacker ‘steal’ hashes from our users,” Coinhive said in a statement.

The company hasn’t revealed how long the unauthorized redirect stayed in place for, but it appears that all coins mined on sites hosting Coinhive’s script were ‘stolen’ during the period, instead of being credited to their accounts.

Coinhive stresses that no user account information was leaked and that its website and database servers were uncompromised. But while that’s good news, the method that the hackers used to access the company’s DNS provider lay in a basic security error.

Back in 2014, crowdfunding platform Kickstarter – which Coinhive used – fell victim to a security breach. After being advised of the fact by law enforcement officials, Kickstarter shut down unauthorized access, began strengthening its systems, while advising customers to do the same.

While Coinhive did respond to the warning to ensure that its data was safe, something slipped through the net. One piece of information – its Cloudflare account password – remained unchanged after the Kickstarter attack. It now seems the most likely culprit for this week’s DNS breach.

“The root cause for this incident was an insecure password for our Cloudflare account that was probably leaked with the Kickstarter data breach back in 2014,” Coinhive says.

“We have learned hard lessons about security and used 2FA and unique passwords with all services since, but we neglected to update our years old Cloudflare account.”

While not mentioning Coinhive explicitly, Kickstarter warned earlier this month that the 2014 incident may not be completely over. In an update posted on the site Oct 6, Kickstarter noted that some of its customers had recently been hearing more information about the breach from notification service Have I been pwned?.

In the meantime, Coinhive has issued an apology and indicated it will find ways to reimburse sites which have lost revenue as a result of the DNS hack.

“We’re deeply sorry about this severe oversight,” the company said. “Our current plan is to credit all sites with an additional 12 hours of their the daily average hashrate. Please give us a few hours to roll this out.”

Based on earlier calculations carried out by TF, The Pirate Bay (if it was mining during the breach) could be potentially owed around $200 for the lost hashes, give or take. After turning off mining in September, the site reactivated it again in October, with no opt-out. The situation appears fluid.

While the hack is obviously a disappointment, Coinhive appears to have advised its users quickly and transparently, which under the circumstances is exactly what’s required. The fact that it’s offering compensation to users will also be welcomed.

The breach is the latest controversy to hit the company. Earlier this month, Cloudflare began banning sites which implemented Coinhive mining without informing their users. The CDN company said it considered non-advised mining as malware.

Source: TF, for the latest info on copyright, file-sharing, torrent sites and ANONYMOUS VPN services.