Tag Archives: AWS IoT Platform*

Managing backend requests and frontend notifications in serverless web apps

Post Syndicated from James Beswick original https://aws.amazon.com/blogs/compute/managing-backend-requests-and-frontend-notifications-in-serverless-web-apps/

Web and mobile applications usually interact with a backend service, often via an API. Many front-end applications pass requests for processing, wait for a result, and then display this to the user. This synchronous approach is only one way to handle messages, but modern applications have alternatives to provide a better user experience.

There are three common ways to make and manage requests from your frontend. This blog post explains the benefits and use-cases of each approach. This post references the Ask Around Me example application, which allows users to ask and answer questions in their local geographic area in real time. To learn more, refer to part 1 of the blog application series.

The synchronous model

The synchronous call is the most common API request pattern, where the caller makes a request to an API and then waits for the response:

Synchronous API example

This type of request is easy to implement and understand because it mirrors the functional call-response pattern many developers are familiar with. The requestor is blocked until the calls completes, so it is well suited to simple requests with short execution times. Use cases include: retrieving the contents of a shopping cart, looking up a value in a database, or submitting an email address from a web form.

However, when your API interacts with other services or external workflows, the synchronous model can have limitations. In the following ecommerce example, any slow performance in the downstream services delays the entire roundtrip performance. Additionally, any outages in one of those services may result in an apparent failure of the entire service.

Tight coupling of services

For services with lengthy workflows, you may reach API Gateway’s 29-second integration timeout. In the following ride sharing example, the service responsible for finding available drivers may have a highly variable response time. This request may time out. It also provides a poor user experience, as there is no feedback to the user for a considerable period.

Lengthy request example

Synchronous requests also have others limitations. You cannot receive more than one response per request, nor can you subscribe to future changes in data. In this example, the API request can only inform callers about drivers at the end of the length process request.

The asynchronous model

Asynchronous tasks are common in serverless applications and distributed applications. They allow separate parts of an application to communicate without needing to wait for a synchronous response. Asynchronous workloads often use queues between services to help manage throughout and assist with retry logic.

With asynchronous tasks, the caller hands off the event and continues on to the next task after receiving the acknowledgment response. The caller does not wait for the entire task to complete. The downstream service works on this event while the caller continues servicing other requests. The ecommerce example, converted to an asynchronous flow, looks like this:

Asynchronous request example

In this example, a caller submits an order and receives a response from API Gateway almost immediately. With service integrations, API Gateway then stores the request directly in a durable store such as Amazon SQS or DynamoDB, before any processing has occurred. This results in a relatively consistent caller response time, regardless of downstream service processing time.

The downstream services fetch messages from the SQS queue or the DynamoDB table for processing. If there is a downstream outage, messages are persisted in the queue and may be retried later. From the user’s perspective, the request has been successfully submitted.

The Ask Around Me application handles the publishing of both questions and answers asynchronously. The API passes the user data to a Lambda function that stores the message in an SQS queue. SQS responds immediately to indicate that the message has been stored successfully, ending the API response. Another Lambda function then takes the messages from the SQS queue and processes these independently.

Ask Around Me save question example

Both synchronous and asynchronous requests are useful for different functions in web applications, so it can be helpful to compare their features and behaviors:

Synchronous requestsAsynchronous requests
The caller waits until the end of processing for a response.The caller receives an acknowledgment quickly while processing continues.
Waiting may incur cost.Minimizes the cost of waiting.
Downstream slowness or outages affects the overall request.Queuing separates ingestion of the request from the processing of the request.
Passes payloads between steps.More often passes transaction identifiers.
Failure affects entire request.Failure only affects segment of request.
Easy to implement.Moderate complexity in implementation

Handling response values and state for asynchronous requests

With asynchronous processes, you cannot pass a return value back to the caller in the same way as you can for synchronous processes. Beyond the initial acknowledgment that the request has been received, there is no return path to provide further information. There are a couple of options available to web and mobile developers to track the state of inflight requests:

  • Polling: the initial request returns a tracking identifier. You create a second API endpoint for the frontend to check the status of the request, referencing the tracking ID. Use DynamoDB or another data store to track the state of the request.
  • WebSocket: this is a bidirectional connection between the frontend client and the backend service. It allows you to send additional information after the initial request is completed. Your backend services can continue to send data back to the client by using a WebSocket connection.

Polling is a simple mechanism to implement for many systems but can result in many empty calls. There is also a delay between data availability and the client being notified. WebSockets provide notifications that are closer to real time and reduce the number of messages between the client and backend system. However, implementing WebSockets is often more complex.

Using AWS IoT Core for real-time messaging

In both the synchronous and asynchronous models, it’s assumed that the caller makes a request and is only interested in the final result of that request. This doesn’t allow for partial information, such as the percentage of a task complete, or being notified continuously as data changes.

Modern web applications commonly use the publish-subscribe pattern to receive notifications as data changes. From receiving alerts when new email arrives to providing dashboard analytics, this method allows for much richer streams of event from backend systems.

In Ask Around Me, the application uses this pattern when listening for new questions from the user’s local area. The frontend subscribes to the geohash value of the user’s location via the AWS SDK. It then waits for messages published by the backend to this topic.

AWS IoT Core between frontend and backend

The SDK automatically manages the WebSocket connection and also handles many common connectivity issues in web apps. The messages are categorized using topics, which are strings defining channels of messages.

The AWS IoT Core service manages broadcasts between backend publishers and frontend subscribers. This enables fan-out functionality, which occurs when multiple subscribers are listening to the same topic. You can broadcast messages to thousands of frontend devices using this mechanism. For web application integration, this is the preferable way to implement publish-subscribe than using Amazon SNS.

The IotData class in the AWS SDK returns a client that uses the MQTT protocol. Once the frontend application establishes the connection, it returns messages, errors, and the connection status via callbacks:

        mqttClient.on('connect', function () {
          console.log('mqttClient connected')

        mqttClient.on('error', function (err) {
          console.log('mqttClient error: ', err)

        mqttClient.on('message', function (topic, payload) {
          const msg = JSON.parse(payload.toString())
          console.log('IoT msg: ', topic, msg)

For more details on how to implement MQTT WebSocket connectivity for your application, see the Ask Around Me sample application code.

Combining multiple approaches for your frontend application

Many frontend applications can combine these models depending on the request type. The Ask Around Me application uses multiple approaches in managing the state of user questions:

Combining multiple models in one application

  1. When the application starts, it retrieves an initial set of questions from the synchronous API endpoint. This returns the available list of questions up to this point in time.
  2. Simultaneously, the frontend subscribes to the geohash topic via AWS IoT Core. Any new questions for this geohash location are sent from the backend processing service to the frontend via this topic. This allows the frontend to receive new questions without subsequent API calls.
  3. When a new question is posted, it is saved to the relevant SQS queue and acknowledged. The question is processed asynchronously by a backend process, which sends updates to the topic.

There are several benefits to combining synchronous, asynchronous, and real-time messaging approaches like this. Most importantly, the user experience remains consistent. The user receives immediate feedback to posting new questions and answers, while longer-running processes are managed asynchronously.

When new information becomes available, the frontend is notified in near-real time. This happens without needing to poll an API endpoint or have the user refresh the user interface. This also reduces the number of unnecessary API calls on the backend service, reducing the cost of running this application. Finally, this uses scalable managed services so the frontend application can support large numbers of users without impacting performance.


Web applications commonly use synchronous APIs when communicating with backend services. For longer-running processes, asynchronous workflows can offer an improved user experience and help manage scaling. By using durable message stores like SQS or DynamoDB, you can separate the request ingestion and response from the request processing.

In this post, I show how modern web applications use real-time messaging via WebSockets to improve the user experience. This provides a transport mechanism for pushing state updates from the backend to the frontend client. The AWS IoT Core service can fan out messages using topics, broadcasting messages to large numbers of frontend subscribers.

To see these three methods in an example frontend application, read more about the Ask Around Me example application.

Implementing geohashing at scale in serverless web applications

Post Syndicated from James Beswick original https://aws.amazon.com/blogs/compute/implementing-geohashing-at-scale-in-serverless-web-applications/

Many web and mobile applications use geospatial data, often used with map overlays. This results in dataset queries based upon proximity, for questions such as “How far is the nearest business?” or “How many users are nearby?” Applications with significant traffic need an efficient way to handle geolocation queries. This blog post explores a simple geohashing solution for serverless applications, and how this can work at scale.

Geohashing is a popular public domain geocode system that converts geographic information into an alphanumeric hash. A geohash is used to identify a rectangular area around a fixed point. The length of the hash determines the precision of the area identified. This allows you to use a hierarchical search where the length of the geohash corresponds to the size of a search area.

This blog post references the Ask Around Me example application, which helps users ask and answer questions in their local geographic area. This post explores a solution suited for the expected volumes in this web application. See part 1 of the blog application series to learn more.

Choosing geohashing precision for your application

One of the most important considerations in using geohashing is understanding the expected distribution of the locations and the size of the search area. Selecting the correct geohash length is important for the efficiency of the search. There is a balance between the number of cells searched and the number of items within each cell.

A geohash corresponds to a grid cell but a typical search corresponds to multiple overlapping cells. In the following diagram, the search radius overlaps nine distinct geohash cells. The query returns all location pins within the cells but only the green pins are relevant to the radial search. The gray pins are outside of the overlapping geohash cells so are immediately discarded in the query:

Discarded pins from a query

If the geohash is too precise, meaning the cell is small, the search radius may include many more cells:

Search radius with too many cells

If the geohash is too coarse, meaning the cell is too large, the query may return too many results for a single cell for the search to be efficient. You may also find a large number of results in those cells are not within the search radius:

Too many results in a single cell

The geohashing algorithm creates a hash that makes it easy to find the neighboring eight cells of any target cell. For optimal performance, you should ideally select a hashing resolution where most queries are resolved by searching only the target cell and its immediate neighbors.

In the canonical implementation of geohash, there are some areas on the globe where physically neighboring cells are not logically close. This can cause errors in these edge cases where there are “seams”. The S2 geometry library solves this problem by using a spherical reference, meaning you can use this approach anywhere in the world. The library has been ported to TypeScript and is available as an npm package called nodes2ts.

Using Amazon DynamoDB for geohashing queries

Amazon DynamoDB is a serverless NoSQL database that offers single-digit millisecond performance at any scale. For an application with moderate load, you can set read and write capacity to allocate a dedicated amount of throughout, or you can set the provisioning to On-Demand. DynamoDB is well suited to key-based queries needing fast, consistent performance.

For web application developers using Node.js or JavaScript, there is an npm package called dynamodb-geo that ports the Java Geo Library for DynamoDB. Both packages are based on the S2 geometry library. This provides a simple interface to use DynamoDB for geospatial data. The library is a wrapper for DynamoDB and maintains an underlying table. After configuring the table and the library, you interact with the data using the library’s API.

For example, to add a new geospatial item:

    // Add a new location to the database
const result = await myGeoTableManager.putPoint({
        RangeKeyValue: { S: 'location-id-1234' }, // unique ID
        GeoPoint: { 
            latitude: 40.6892534,
            longitude: -74.0466891
        PutItemInput: { 
            Item: { 
                country: { S: 'USA' },
                state: { S: 'New York' },
                pointOfInterest: { S: 'Statue of Liberty' }

The library also provides methods for updating and deleting data points, and supports DynamoDB batch operations. Querying the data via the API can only be done via geo-point requests. You can retrieve a dataset of items based around a rectangular or radial area:

    // Querying 10km (~6.2 miles) around Boston, Massachusetts.

    const result = await myGeoTableManager.queryRadius({
        RadiusInMeter: 10000,
        CenterPoint: {
            latitude: 42.3145186,
            longitude: -71.1103666

    // Outputs results as an array of DynamoDB.AttributeMaps

Moving locations and moving consumers

In Ask Around Me, questions have a fixed latitude and longitude – once a question is asked, the location never changes. The dynamodb-geo library uses the hashKey as a primary key in the underlying DynamoDB table. To update the primary key of a DynamoDB item, you must delete and recreate the entire item.

Many geolocation implementations use static data, such as a list of retail store locations. But if you need to track moving locations, such as the location of mobile users, this is not the best approach. As a result, this library works well for static data (or data where the location rarely changes) but is not suitable where locations change frequently.

In the Ask Around Me app, users receive alerts when new questions appear around their current location. Real-time messaging is implemented using AWS IoT Core, where publish-subscribe topics connect the frontend and backend.

The application retrieves the current latitude and longitude via the browser and uses the S2 geometry library to convert this to a geohash key. It then subscribes to this geohash topic. On the backend, when new questions are saved, these are published to a topic using the geohash key. As a result, users in the same geohash area receive notifications when new questions are asked nearby.

This broadcast pattern allows the application to fan out a single new question in the DynamoDB table to thousands of live users in frontend application. As users move their location, the front-end application can detect if they moved from one geohash cell to another. If so, the frontend unsubscribes from the outdated geohash identifier, and subscribes to the new. This ensures that moving consumers are always listening to questions near their current location. For more information on the broadcast pattern, see the AWS whitepaper, Designing MQTT Topics for AWS IoT Core.

Sorting, aging, and expiring location data

For an application with many writes to the underlying geolocation table, the user may expect to see newer data first. Also, you may need a strategy for removing stale data from the table. Even with a highly performant database like DynamoDB, you must ensure the first page of results return the most relevant items.

The dynamodb-geo library uses the geohash identifier as a primary key, but allows the developer to choose an identifying range key. You need this key to uniquely identify items that have the same geohash. However, you can also use this key to for sorting and paging data that’s returned by the library’s search APIs.

The Ask Around Me app uses a concatenated userId-timestamp pattern as a range key, for example jbeswick-1589202456. This helps in implementing two data access patterns:

  • Finding by user: using the begins_with operator, you can identify questions asked by a specific user. For example, begins_with(‘jbeswick’) returns all the questions for this user.
  • Sorting results by time added: as query results are always sorted by the sort key value, the Unix timestamp ensures that these are returned from oldest to newest. You can reverse this order to return newest first by setting ScanIndexForward to false in the DynamoDB query.

In this application, you might decide that questions more than a year old should be expired from the table. You can have DynamoDB expire items automatically using the time to live (TTL) feature.

To use this, create a custom numeric attribute in the table that contains the expiration time of the item, set as a Unix timestamp. For example, an item expiring on a midnight on January 1, 2023 uses the timestamp 1672531200.

When you enable TTL on a DynamoDB table, you specify which attribute contains the expiration value. A background job checks the TTL values against the current time. For any items found where the TTL timestamp is older than the current time, it expires those items within a 48-hour time window.


This blog post explores how you can solve geolocation queries using geohashing. I discuss how you should decide on the resolution of a geohash for your specific workload.

I explain why DynamoDB is a good fit for many geohashing applications. I cover how you can use the dynamodb-geo library to easily implement location queries in your web applications. Using AWS IoT Core, you can also use MQTT topics to fan out updates to moving subscribers.

Finally, I show how to use the DynamoDB table’s range key to help with sorting data by age and supporting addition access patterns. For application with many writes, you can also automatically expire items using DynamoDB’s TTL feature.

To learn more about how the Ask Around Me application implements geolocation queries, see the blog series.

Building a location-based, scalable, serverless web app – part 3

Post Syndicated from James Beswick original https://aws.amazon.com/blogs/compute/building-a-location-based-scalable-serverless-web-app-part-3/

In part 2, I cover the API configuration, geohashing algorithm, and real-time messaging architecture used in the Ask Around Me web application. These are needed for receiving and processing questions and answers, and sending results back to users in real time.

In this post, I explain the backend processing architecture, how data is aggregated, and how to deploy the final application to production. The code and instructions for this application are available in the GitHub repo.

Processing questions

The frontend sends new user questions to the backend via the POST questions API. While the predicted volume of questions is only 1,000 per hour, it’s possible for usage to spike unexpectedly. To help handle this load, the PostQuestions Lambda function puts incoming questions onto an Amazon SQS queue. The ProcessQuestions function takes messages from the Questions queue in batches of 10, and loads these into the Questions table in Amazon DynamoDB.

Questions processing architecture

This asynchronous process smooths out traffic spikes, ensuring that the application is not throttled by DynamoDB. It also provides consistent response times to the front-end POST request, since the API call returns as soon as the message is durably persisted to the queue.

Currently, the ProcessQuestions function does not parse or validate user questions. It would be easy to add message filtering at this stage, using Amazon Comprehend to detect sentiment or inappropriate language. These changes would increase the processing time per question, but by handling this asynchronously, the initial POST API latency is not adversely affected.

The ProcessQuestions function uses the Geo Library for Amazon DynamoDB that converts the question’s latitude and longitude into a geohash. This geohash attribute is one of the indexes in the underlying DynamoDB table. The GetQuestions function using the same library for efficiently querying questions based on proximity to the user.

There are a couple of different mechanisms used to pass information between the frontend and backend applications. When the frontend first initializes, it retrieves the current location of the user from the browser. It then calls the questions API to get a list of active questions within 5 miles of the current location. This retrieves the state up to this point in time. To receive notifications of new messages posted in the user’s area, the frontend also subscribes to the geohash topic in AWS IoT Core.

Processing answers

Answers processing architecture

The application allows two types of question that have different answer types. First, the rating questions accept an answer with a 0–5 score range. Second, the geography questions accept a geo-point, which is a latitude and longitude representing a location.

Similar to the way questions are handled, answers are also queued before processing. However, the PostAnswers Lambda function sends answers to different queues, depending on question type. Ratings messages are sent to the StarAnswers queue, while geography messages are routed to the GeoAnswers queue. Star ratings are saved as raw data in the Answers table by the ProcessAnswerStar function. Geography answers are first converted to a geohash before they are stored.

It’s possible for users to submit updates to their answers. For a star rating, the processing function simply saves the new score. For geography answers, if the updated answer contains a latitude and longitude close enough to the original answer, it results in the same geohash. This is due to the different aggregation processes used for these types of answers.

Aggregating data

In this application, the users asking questions are seeking aggregated answers instead of raw data. For example, “How do you rate the park?” shows an average score from users instead of thousands of individual ratings. To maintain performance, this aggregation occurs when new answers are saved to the database, not when the application fetches the question list.

The Answers table emits updates to a DynamoDB stream whenever new items are inserted or updated. The StreamSpecification parameter in the table definition is set to NEW_AND_OLD_IMAGES, meaning the stream record contains both the new and old item record.

New answers to questions are new items in the table, so the stream record only contains the new image. If users update their answers, this creates an updated item in the table, and the stream record contains both the new and old images of the item.

For star ratings, when receiving an updated rating, the Aggregation function uses both images to calculate the delta in the score. For example, if the old rating was 2 and the user changes this to 5, then the delta is 3. The summary score related to the answer is updated in the Questions table, using a DynamoDB update expression:

    const result = await myGeoTableManager.updatePoint({
      RangeKeyValue: { S: update }, 
      GeoPoint: {
        latitude: item.lat,
        longitude: item.lng
      UpdateItemInput: {
        UpdateExpression: 'ADD answers :deltaAnswers, totalScore :deltaTotalScore',
        ExpressionAttributeValues: {
          ':deltaAnswers': { N: item.deltaAnswers.toString()},
          ':deltaTotalScore': { N: item.deltaValue.toString()}

For geo-point ratings, the same approach is used but if the geohash changes, then the delta is -1 for the geohash in the old image, and +1 for the geohash in the new image. The update expression automatically creates a new geohash attribute on the DynamoDB item if it is not already present:

    const result = await myGeoTableManager.updatePoint({
      RangeKeyValue: { S: item.ID }, 
      GeoPoint: {
        latitude: item.lat,
        longitude: item.lng
      UpdateItemInput: {
        UpdateExpression: `ADD ${item.geohash} :deltaAnswers, answers :deltaAnswers`,
        ExpressionAttributeValues: {
          ':deltaAnswers': { N: item.deltaAnswers.toString() }          

By using a Lambda function as a DynamoDB stream processor, you can aggregate large amounts of data in near real time. The Questions and Answers tables have a one-to-many relationship – many answers belong to one question. As answers are saved, the aggregation process updates the summaries in the Questions table.

The Questions table also publishes updates to another DynamoDB stream. These are consumed by a Lambda function that sends the aggregated update to topics in AWS IoT Core. This is how updated scores are sent back to the frontend client application.

Publishing to production with Amplify Console

At this point, you can run the application on your local development machine and view the application via the localhost Vue.js server. Once you are ready to launch the application to users, you must deploy to production.

Single-page applications are easy to deploy publicly. The build process creates static HTML, JS, and CSS files. These can be served via Amazon S3 and Amazon CloudFront, together with any image and media assets used. The process of running the build process and managing the deployment can be automated using AWS Amplify Console.

In this walk through, I use GitHub as the repo provider. You can also use AWS CodeCommit, Bitbucket, GitLab, or upload the build directory from your machine.

To deploy the front end via Amplify Console:

  1. From the AWS Management Console, select the Services dropdown and choose AWS Amplify. From the initial splash screen, choose Get Started under Deploy.Amplify Console getting started
  2. Select GitHub as the repository provider, then choose Continue:Select GitHub as your code repo
  3. Follow the prompts to enable GitHub access, then select the repository dropdown and choose the repo. In the Branch dropdown, choose master. Choose Next.Add repository branch
  4. In the App build and test settings page, choose Next.
  5. In the Review page, choose Save and deploy.
  6. The final screen shows the deployment pipeline for the connected repo, starting at the Provision phase:Amplify Console deployment pipeline

After a few minutes, the Build, Deploy, and Verify steps show green checkmarks. Open the URL in a browser, and you see that the application is now served by the public URL:

Ask Around Me - Deployed application

Finally, before logging in, you must add the URL to the list of allowed URLs in the Auth0 settings:

  1. Log into Auth0 and navigate to the dashboard.
  2. Choose Applications in the menu, then select Ask Around Me from the list of applications.
  3. On the Settings tab, add the application’s URL to Allowed Callback URLs, Allowed Logout URLs, and Allowed Web Origins. Separate from the existing values using a comma.Updating the Auth0 configuration
  4. Choose Save changes. This allows the new published domain name to interact with Auth0 for authentication your application’s users.

Anytime you push changes to the code repository, Amplify Console detects the commit and redeploys the application. If errors are detected, the existing version is presented to users. If there are no errors, the new version is served to visitors.


In the last part of this series, I show how the application queues posted questions and answers. I explain how this asynchronous approach smooths traffic spikes and helps maintain responsive APIs.

I cover how answers are collected from thousands of users and are aggregated using DynamoDB streams. These totals are saved as summaries in the Questions table, and live updates are pushed via AWS IoT Core back to the frontend.

Finally, I show how you can automate deployment using Amplify Console. By connecting the service directly with your code repository, it publishes and serves your application with no need to manually copy files.

To learn more about this application, see the accompanying GitHub repo.

Building a location-based, scalable, serverless web app – part 2

Post Syndicated from James Beswick original https://aws.amazon.com/blogs/compute/building-a-location-based-scalable-serverless-web-app-part-2/

Part 1 introduces the Ask Around Me web application that allows users to send questions to other local users in real time. I explain the app’s functionality and how using a single-page application (SPA) framework complements a serverless backend. I configure Auth0 for authentication and show how to deploy the frontend and backend. I also introduce how SPA frontends can send and receive data using both a traditional API and real-time messaging via a WebSocket.

In this post, I review the backend architecture, Amazon API Gateway’s HTTP APIs, and the geohashing implementation. The code and instructions for this application are available in the GitHub repo.

Architecture overview

After deploying the application using the repo’s README.md instructions, the backend architecture looks like this:

Ask Around Me backend architecture

The Vue.js frontend primarily interacts with the backend via HTTP APIs using Amazon API Gateway. When users submit questions or answers, the data is sent via the POST API endpoints. When the frontend requests lists of questions or answers, this occurs via the GET API endpoints.

Incoming questions and answers are posted to separate Amazon SQS queues. These queues invoke AWS Lambda functions that process and store the data in the application’s Amazon DynamoDB tables. In the Questions table, the application saves geo-location data and aggregated statistics for each question. The Answers table maintains a record of user IDs and answers to ensure that each user can only post one answer per question.

When new answers are stored in the Answers tables, a DynamoDB stream triggers a Lambda aggregation function with the update. This calculates average scores for questions and aggregates data for the heat map, then stores the result in the main Questions table. When the Questions table is updated, this DynamoDB stream invokes the Publish Lambda function. This publishes updates to the relevant topic in AWS IoT Core, which the front-end application subscribes to.


API Gateway is a common integration service used between the frontend and backend of serverless web applications. You can choose between the standard REST APIs, and the newer HTTP APIs. The choice depends upon which features you need, and cost considerations for your workload.

This application uses JWT authentication via Auth0 and Lambda proxy integration, and both are supported by HTTP APIs. Many advanced features like API key management, Amazon Cognito integration, and usage plans are not required in this application. It’s also important to compare to cost of each service:

API typeHourlyDaily Annually
PUT questions1,00024,0008,760,000
GET questions50,0001,200,000438,000,000
PUT answers10,000240,00087,600,000
Total API requests 534,360,000
REST APIs cost$1,870.26
HTTP APIs$534.36

Using the predicted API usage covered in part 1, you can compare the REST APIs and HTTP APIs overall cost. At an estimated $534 annually, the HTTP APIs option is approximately 30% of the cost of REST APIs.

The AWS Serverless Application Model (SAM) template in the repo defines the HTTP API resource and CORS configuration. It also includes the Auth0 authorizer used to validate each API request:

    Type: AWS::Serverless::HttpApi
              issuer: !Ref Auth0issuer
                - https://auth0-jwt-authorizer
            IdentitySource: "$request.header.Authorization"
        DefaultAuthorizer: MyAuthorizer

          - GET
          - POST
          - DELETE
          - OPTIONS
          - "*"   
          - "*"   

With the HTTP API resource defined, each Lambda function has an event configuration referencing this resource. All the functions referencing the HTTP API resource automatically use the Auth0 authorizer.

    Type: AWS::Serverless::Function
      Description: Get all answers for a question
          Type: HttpApi
            Path: /answers/{Key}
            Method: get
            ApiId: !Ref MyApi    

Using geohashing in web applications

A key part of the functionality in Ask Around Me is the ability to find and answer questions near the user. Given the expected volume of questions in this system, this requires an efficient way to query based upon location that maintains performance as traffic grows.

In a naïve implementation, you might compare the current geographical position of the user with the geo-location of each question and answer in the database. But with an expected 1,000 questions per hour, this would soon become a slow operation with O(n) performance.

A more efficient solution is geohashing. This divides the geographical area of the planet into series of grid cells that are identified by an alphanumeric hash. The first character of the hash identifies one of 32 cells in the grid, roughly 5000 km x 5000 km on the planet. The second character identifies one of 32 squares in that first cell, so combining the first two characters provides a resolution of approximately 1250 km x 1250 km. By the 12th character in the hash, you can identify an area as small as a couple of square inches on Earth. For a more detailed explanation, see this geohashing site.

When using this algorithm, it’s important to choose the correct level of resolution. For Ask Around Me, the frontend searches for questions within 5 miles of the user. You can identify these areas with a 5-character hash. This means you can compare the user’s current location using their geohash, to the geohash stored in the Questions table. This comparison allows you to immediately discard most questions from the search and quickly find the relevant items.

This solution uses the Geo Library for Amazon DynamoDB npm library. Both the GET and POST questions APIs use this library to calculate the geohash when storing and fetching questions. The library requires a dedicated DynamoDB table, which is why user answers are stored in a separate table.

The GET questions API uses the latitude and longitude from the query parameters to query the underlying DynamoDB using this library:

const AWS = require('aws-sdk')
AWS.config.update({region: process.env.AWS_REGION})

const ddb = new AWS.DynamoDB() 
const ddbGeo = require('dynamodb-geo')
const config = new ddbGeo.GeoDataManagerConfiguration(ddb, process.env.TableName)
config.hashKeyLength = 5

const myGeoTableManager = new ddbGeo.GeoDataManager(config)

exports.handler = async (event) => {

  const latitude = parseFloat(event.queryStringParameters.lat)
  const longitude = parseFloat(event.queryStringParameters.lng)

  // Get questions within geo range
  const result = await myGeoTableManager.queryRadius({
    CenterPoint: {

  return {
    statusCode: 200,
    body: JSON.stringify(result)

The publish/subscribe pattern for real time in web apps

Modern web applications frequently use real-time notifications to keep users informed of state changes. You could achieve this with frequently polling of the APIs to fetch new information. However, this approach is usually wasteful, both in cost and compute terms, because most API calls do not return new information. Additionally, if updates are evenly distributed and you poll every n seconds, there is an average delay of n/2 seconds between data becoming available and your application receiving it.

Instead of polling, a better option for many web applications is a WebSocket. Data availability is closer to real time, and the messaging is less frequent. This can be important for web applications used on mobile devices where unnecessary messaging can impact battery life.

This approach uses the publish-subscribe pattern. The frontend makes subscriptions to a backend service, indicating topics of interest. The backend service receives messages from publishers, which are upstream processes in the application. It filters the messages and routes to the appropriate subscribers.

Although powerful, this can be complex to implement due to connectivity issues over networks. For a web application, users may turn off their devices, disconnect Wi-Fi, or become unreachable due to limited coverage. This pattern is generally forward-only, meaning you only receive messages after the point of subscription.

AWS IoT Core simplifies this process, and the JavaScript SDK handles the common reconnection issues. The backend application sends messages to topics in AWS IoT Core, and the frontend application subscribes to topics of interest. The service maintains the list of active publishers and subscribers, and routes messages between the two. It also automatically manages fan-out, which occurs when there are many subscribers to a single topic.

From a pricing perspective, this is also a cost-efficient approach. At the time of writing, AWS IoT Core costs $0.08 per million minutes of connection, and $1.00 per million messages. There are also no servers to manage, and the service scales automatically to handle your application’s load.

In the example application, the real-time connection is configured and managed in a single component, IoT.vue. This initiates a connection to an IoT endpoint when the application first starts, and listens for messages on subscribed topics. It passes data back to the global Vuex store so other components automatically receive updates with no dependency on the IoT component.

Choosing publish-subscribe topics for web apps

In a typical synchronous API call, the client application makes a specific request and receives a response from a backend service. With a topic-based subscription, the topic itself is the equivalent of the request, but you usually don’t receive immediate information.

In this web application, there are a number of topics that are potentially important to users. Some topics are shared across multiple users, while other are private to a single user:

  • Account-level topic: messages relating only to a single user ID, such as billing and notifications. These are intended for any devices where that user is logged in.
  • Per-question topic: when a user asks a question, they need alerts when new answers arrive. Each question ID maps to an individual topic. Anyone who asks or watches a question subscribes to this topic.
  • Geo-fenced alert topic: a user receives alerts when new questions are asked in their local area. In this case, the geohash of their location is the topic identifier. New questions are published to their geohash topics, and users within the same geohash area receive those messages.
  • A system-wide topic: this is a single topic that all users subscribe to. This is reserved for important messages for all application users.

In web applications, you subscribe to some topics when the application initializes, such as account-level or system-wide topics. Other subscriptions are dynamic. For example, you subscribe to a question ID topic only after posting a question, or subscribe to different geo-fence hashes when the user’s location changes.


This post explores the backend architecture of the Ask Around Me application. I compare the cost and features in deciding between REST APIs and HTTP APIs in API Gateway. I introduce geohashing and the npm library used to handle geo-location queries in DynamoDB. And I show how you can build real-time messaging into your web applications using the publish-subscribe pattern with AWS IoT Core.

To learn more, visit the application’s code repo on GitHub.

Building a Raspberry Pi telepresence robot using serverless: Part 1

Post Syndicated from Moheeb Zara original https://aws.amazon.com/blogs/compute/building-a-raspberry-pi-telepresence-robot-using-serverless-part-1/

A Pimoroni STS-Pi Robot Kit connected to AWS for remote control and viewing.

A Pimoroni STS-Pi Robot Kit connected to AWS for remote control and viewing.

A telepresence robot allows you to explore remote environments from the comfort of your home through live stream video and remote control. These types of robots can improve the lives of the disabled, elderly, or those that simply cannot be with their coworkers or loved ones in person. Some are used to explore off-world terrain and others for search and rescue.

This guide walks through building a simple telepresence robot using a Pimoroni STS-PI Raspberry Pi robot kit. A Raspberry Pi is a small low-cost device that runs Linux. Add-on modules for Raspberry Pi are called “hats”. You can substitute this kit with any mobile platform that uses two motors wired to an Adafruit Motor Hat or a Pimoroni Explorer Hat.

The sample serverless application uses AWS Lambda and Amazon API Gateway to create a REST API for driving the robot. A Python application running on the robot uses AWS IoT Core to receive drive commands and authenticate with Amazon Kinesis Video Streams with WebRTC using an IoT Credentials Provider. In the next blog I walk through deploying a web frontend to both view the livestream and control the robot via the API.


You need the following to complete the project:

A Pimoroni STS-Pi robot kit, Explorer Hat, Raspberry Pi, camera, and battery.

A Pimoroni STS-Pi robot kit, Explorer Hat, Raspberry Pi, camera, and battery.

Estimated Cost: $120

There are three major parts to this project. First deploy the serverless backend using the AWS Serverless Application Repository. Then assemble the robot and run an installer on the Raspberry Pi. Finally, configure and run the Python application on the robot to confirm it can be driven through the API and is streaming video.

Deploy the serverless application

In this section, use the Serverless Application Repository to deploy the backend resources for the robot. The resources to deploy are defined using the AWS Serverless Application Model (SAM), an open-source framework for building serverless applications using AWS CloudFormation. To deeper understand how this application is built, look at the SAM template in the GitHub repository.

An architecture diagram of the AWS IoT and Amazon Kinesis Video Stream resources of the deployed application.

The Python application that runs on the robot requires permissions to connect as an IoT Thing and subscribe to messages sent to a specific topic on the AWS IoT Core message broker. The following policy is created in the SAM template:

      Type: "AWS::IoT::Policy"
        PolicyName: !Sub "${RobotName}Policy"
          Version: "2012-10-17"
            - Effect: Allow
                - iot:Connect
                - iot:Subscribe
                - iot:Publish
                - iot:Receive
                - !Sub "arn:aws:iot:*:*:topicfilter/${RobotName}/action"
                - !Sub "arn:aws:iot:*:*:topic/${RobotName}/action"
                - !Sub "arn:aws:iot:*:*:topic/${RobotName}/telemetry"
                - !Sub "arn:aws:iot:*:*:client/${RobotName}"

To transmit video, the Python application runs the amazon-kinesis-video-streams-webrtc-sdk-c sample in a subprocess. Instead of using separate credentials to authenticate with Kinesis Video Streams, a Role Alias policy is created so that IoT credentials can be used.

  "Version": "2012-10-17",
  "Statement": [
      "Action": [
      "Resource": "arn:aws:iot:Region:AccountID:rolealias/robot-camera-streaming-role-alias",
      "Effect": "Allow"

When the above policy is attached to a certificate associated with an IoT Thing, it can assume the following role:

      Type: 'AWS::IAM::Role'
          Version: '2012-10-17'
          - Effect: 'Allow'
              Service: 'credentials.iot.amazonaws.com'
            Action: 'sts:AssumeRole'
        - PolicyName: !Sub "KVSIAMPolicy-${AWS::StackName}"
            Version: '2012-10-17'
            - Effect: Allow
                - kinesisvideo:ConnectAsMaster
                - kinesisvideo:GetSignalingChannelEndpoint
                - kinesisvideo:CreateSignalingChannel
                - kinesisvideo:GetIceServerConfig
                - kinesisvideo:DescribeSignalingChannel
              Resource: "arn:aws:kinesisvideo:*:*:channel/${credentials-iot:ThingName}/*"

This role grants access to connect and transmit video over WebRTC using the Kinesis Video Streams signaling channel deployed by the serverless application. An architecture diagram of the API endpoint in the deployed application.

A deployed API Gateway endpoint, when called with valid JSON, invokes a Lambda function that publishes to an IoT message topic, RobotName/action. The Python application on the robot subscribes to this topic and drives the motors based on any received message that maps to a command.

  1. Navigate to the aws-serverless-telepresence-robot application in the Serverless Application Repository.
  2. Choose Deploy.
  3. On the next page, under Application Settings, fill out the parameter, RobotName.
  4. Choose Deploy.
  5. Once complete, choose View CloudFormation Stack.
  6. Select the Outputs tab. Copy the ApiURL and the EndpointURL for use when configuring the robot.

Create and download the AWS IoT device certificate

The robot requires an AWS IoT root CA (fetched by the install script), certificate, and private key to authenticate with AWS IoT Core. The certificate and private key are not created by the serverless application since they can only be downloaded on creation. Create a new certificate and attach the IoT policy and Role Alias policy deployed by the serverless application.

  1. Navigate to the AWS IoT Core console.
  2. Choose Manage, Things.
  3. Choose the Thing that corresponds with the name of the robot.
  4. Under Security, choose Create certificate.
  5. Choose Activate.
  6. Download the Private Key and Thing Certificate. Save these securely, as this is the only time you can download this certificate.
  7. Choose Attach Policy.
  8. Two policies are created and must be attached. From the list, select
  9. Choose Done.

Flash an operating system to an SD card

The Raspberry Pi single-board Linux computer uses an SD card as the main file system storage. Raspbian Buster Lite is an officially supported Debian Linux operating system that must be flashed to an SD card. Balena.io has created an application called balenaEtcher for the sole purpose of accomplishing this safely.

  1. Download the latest version of Raspbian Buster Lite.
  2. Download and install balenaEtcher.
  3. Insert the SD card into your computer and run balenaEtcher.
  4. Choose the Raspbian image. Choose Flash to burn the image to the SD card.
  5. When flashing is complete, balenaEtcher dismounts the SD card.

Configure Wi-Fi and SSH headless

Typically, a keyboard and monitor are used to configure Wi-Fi or to access the command line on a Raspberry Pi. Since it is on a mobile platform, configure the Raspberry Pi to connect to a Wi-Fi network and enable remote access headless by adding configuration files to the SD card.

  1. Re-insert the SD card to your computer so that it shows as volume boot.
  2. Create a file in the boot volume of the SD card named wpa_supplicant.conf.
  3. Paste in the following contents, substituting your Wi-Fi credentials.
    ctrl_interface=DIR=/var/run/wpa_supplicant GROUP=netdev
            country=<Insert country code here>
             ssid="<Name of your WiFi>"
             psk="<Password for your WiFi>"

  4. Create an empty file without a file extension in the boot volume named ssh. At boot, the Raspbian operating system looks for this file and enables remote access if it exists. This can be done from a command line:
    cd path/to/volume/boot
    touch ssh

  5. Safely eject the SD card from your computer.

Assemble the robot

For this section, you can use the Pimoroni STS-Pi robot kit with a Pimoroni Explorer Hat, along with a Raspberry Pi Model 3 B+ or newer, and a camera module. Alternatively, you can use any two motor robot platform that uses the Explorer Hat or Adafruit Motor Hat.

  1. Follow the instructions in this video to assemble the Pimoroni STS-Pi robot kit.
  2. Place the SD card in the Raspberry Pi.
  3. Since the installation may take some time, power the Raspberry Pi using a USB 5V power supply connected to a wall plug rather than a battery.

Connect remotely using SSH

Use your computer to gain remote command line access of the Raspberry Pi using SSH. Both devices must be on the same network.

  1. Open a terminal application with SSH installed. It is already built into Linux and Mac OS, to enable SSH on Windows follow these instructions.
  2. Enter the following to begin a secure shell session as user pi on the default local hostname raspberrypi, which resolves to the IP address of the device using MDNS:
  3. If prompted to add an SSH key to the list of known hosts, type yes.
  4. When prompted for a password, type raspberry. This is the default password and can be changed using the raspi-config utility.
  5. Upon successful login, you now have shell access to your Raspberry Pi device.

Enable the camera using raspi-config

A built-in utility, raspi-config, provides an easy to use interface for configuring Raspbian. You must enable the camera module, along with I2C, a serial bus used for communicating with the motor driver.

  1. In an open SSH session, type the following to open the raspi-config utility:
    sudo raspi-config

  2. Using the arrows, choose Interfacing Options.
  3. Choose Camera. When prompted, choose Yes to enable the camera module.
  4. Repeat the process to enable the I2C interface.
  5. Select Finish and reboot.

Run the install script

An installer script is provided for building and installing the Kinesis Video Stream WebRTC producer, AWSIoTPythonSDK and Pimoroni Explorer Hat Python libraries. Upon completion, it creates a directory with the following structure:

├── /home/pi/Projects/robot
│  └── main.py // The main Python application
│  └── config.json // Parameters used by main.py
│  └── kvsWebrtcClientMasterGstSample //Kinesis Video Stream producer
│  └── /certs
│     └── cacert.pem // Amazon SFSRootCAG2 Certificate Authority
│     └── certificate.pem // AWS IoT certificate placeholder
│     └── private.pem.key // AWS IoT private key placeholder
  1. Open an SSH session on the Raspberry Pi.
  2. (Optional) If using the Adafruit Motor Hat, run this command, otherwise the script defaults to the Pimoroni Explorer Hat.
    export MOTOR_DRIVER=adafruit  

  3. Run the following command to fetch and execute the installer script.
    wget -O - https://raw.githubusercontent.com/aws-samples/aws-serverless-telepresence-robot/master/scripts/install.sh | bash

  4. While the script installs, proceed to the next section.

Configure the code

The Python application on the robot subscribes to AWS IoT Core to receive messages. It requires the certificate and private key created for the IoT thing to authenticate. These files must be copied to the directory where the Python application is stored on the Raspberry Pi.

It also requires the IoT Credentials endpoint is added to the file config.json to assume permissions necessary to transmit video to Amazon Kinesis Video Streams.

  1. Open an SSH session on the Raspberry Pi.
  2. Open the certificate.pem file with the nano text editor and paste in the contents of the certificate downloaded earlier.
    nano certificate.pem

  3. Press CTRL+X and then Y to save the file.
  4. Repeat the process with the private.key.pem file.
    nano private.key.pem

  5. Open the config.json file.
    nano config.json

  6. Provide the following information:
    IOT_THINGNAME: The name of your robot, as set in the serverless application.
    IOT_CORE_ENDPOINT: This is found under the Settings page in the AWS IoT Core console.
    IOT_GET_CREDENTIAL_ENDPOINT: Provided by the serverless application.
    ROLE_ALIAS: This is already set to match the Role Alias deployed by the serverless application.
    AWS_DEFAULT_REGION: Corresponds to the Region the application is deployed in.
  7. Save the file using CTRL+X and Y.
  8. To start the robot, run the command:
    python3 main.py

  9. To stop the script, press CTRL+C.

View the Kinesis video stream

The following steps create a WebRTC connection with the robot to view the live stream.

  1. Navigate to the Amazon Kinesis Video Streams console.
  2. Choose Signaling channels from the left menu.
  3. Choose the channel that corresponds with the name of your robot.
  4. Open the Media Playback card.
  5. After a moment, a WebRTC peer to peer connection is negotiated and live video is displayed.
    An animated gif demonstrating a live video stream from the robot.

Sending drive commands

The serverless backend includes an Amazon API Gateway REST endpoint that publishes JSON messages to the Python script on the robot.

The robot expects a message:

{ “action”: <direction> }

Where direction can be “forward”, “backwards”, “left”, or “right”.

  1. While the Python script is running on the robot, open another terminal window.
  2. Run this command to tell the robot to drive forward. Replace <API-URL> using the endpoint listed under Outputs in the CloudFormation stack for the serverless application.
    curl -d '{"action":"forward"}' -H "Content-Type: application/json" -X POST https://<API-URL>/publish

    An animated gif demonstrating the robot being driven from a REST request.


In this post, I show how to build and program a telepresence robot with remote control and a live video feed in the cloud. I did this by installing a Python application on a Raspberry Pi robot and deploying a serverless application.

The Python application uses AWS IoT credentials to receive remote commands from the cloud and transmit live video using Kinesis Video Streams with WebRTC. The serverless application deploys a REST endpoint using API Gateway and a Lambda function. Any application that can connect to the endpoint can drive the robot.

In part two, I build on this project by deploying a web interface for the robot using AWS Amplify.

A preview of the web frontend built in the next blog.

A preview of the web frontend built in the next blog.



Building an AWS IoT Core device using AWS Serverless and an ESP32

Post Syndicated from Moheeb Zara original https://aws.amazon.com/blogs/compute/building-an-aws-iot-core-device-using-aws-serverless-and-an-esp32/

Using a simple Arduino sketch, an AWS Serverless Application Repository application, and a microcontroller, you can build a basic serverless workflow for communicating with an AWS IoT Core device.

A microcontroller is a programmable chip and acts as the brain of an electronic device. It has input and output pins for reading and writing on digital or analog components. Those components could be sensors, relays, actuators, or various other devices. It can be used to build remote sensors, home automation products, robots, and much more. The ESP32 is a powerful low-cost microcontroller with Wi-Fi and Bluetooth built in and is used this walkthrough.

The Arduino IDE, a lightweight development environment for hardware, now includes support for the ESP32. There is a large collection of community and officially supported libraries, from addressable LED strips to spectral light analysis.

The following walkthrough demonstrates connecting an ESP32 to AWS IoT Core to allow it to publish and subscribe to topics. This means that the device can send any arbitrary information, such as sensor values, into AWS IoT Core while also being able to receive commands.

Solution overview

This post walks through deploying an application from the AWS Serverless Application Repository. This allows an AWS IoT device to be messaged using a REST endpoint powered by Amazon API Gateway and AWS Lambda. The AWS SAR application also configures an AWS IoT rule that forwards any messages published by the device to a Lambda function that updates an Amazon DynamoDB table, demonstrating basic bidirectional communication.

The last section explores how to build an IoT project with real-world application. By connecting a thermal printer module and modifying a few lines of code in the example firmware, the ESP32 device becomes an AWS IoT–connected printer.

All of this can be accomplished within the AWS Free Tier, which is necessary for the following instructions.

An example of an AWS IoT project using an ESP32, AWS IoT Core, and an Arduino thermal printer

An example of an AWS IoT project using an ESP32, AWS IoT Core, and an Arduino thermal printer.

Required steps

To complete the walkthrough, follow these steps:

  • Create an AWS IoT device.
  • Install and configure the Arduino IDE.
  • Configure and flash an ESP32 IoT device.
  • Deploying the lambda-iot-rule AWS SAR application.
  • Monitor and test.
  • Create an IoT thermal printer.

Creating an AWS IoT device

To communicate with the ESP32 device, it must connect to AWS IoT Core with device credentials. You must also specify the topics it has permissions to publish and subscribe on.

  1. In the AWS IoT console, choose Register a new thing, Create a single thing.
  2. Name the new thing. Use this exact name later when configuring the ESP32 IoT device. Leave the remaining fields set to their defaults. Choose Next.
  3.  Choose Create certificate. Only the thing cert, private key, and Amazon Root CA 1 downloads are necessary for the ESP32 to connect. Download and save them somewhere secure, as they are used when programming the ESP32 device.
  4. Choose Activate, Attach a policy.
  5. Skip adding a policy, and choose Register Thing.
  6. In the AWS IoT console side menu, choose Secure, Policies, Create a policy.
  7. Name the policy Esp32Policy. Choose the Advanced tab.
  8. Paste in the following policy template.
      "Version": "2012-10-17",
      "Statement": [
          "Effect": "Allow",
          "Action": "iot:Connect",
          "Resource": "arn:aws:iot:REGION:ACCOUNT_ID:client/THINGNAME"
          "Effect": "Allow",
          "Action": "iot:Subscribe",
          "Resource": "arn:aws:iot:REGION:ACCOUNT_ID:topicfilter/esp32/sub"
          "Effect": "Allow",
          "Action": "iot:Receive",
          "Resource": "arn:aws:iot:REGION:ACCOUNT_ID:topic/esp32/sub"
          "Effect": "Allow",
          "Action": "iot:Publish",
          "Resource": "arn:aws:iot:REGION:ACCOUNT_ID:topic/esp32/pub"
  9. Replace REGION with the matching AWS Region you’re currently operating in. This can be found on the top right corner of the AWS console window.
  10.  Replace ACCOUNT_ID with your own, which can be found in Account Settings.
  11. Replace THINGNAME with the name of your device.
  12. Choose Create.
  13. In the AWS IoT console, choose Secure, Certification. Select the one created for your device and choose Actions, Attach policy.
  14. Choose Esp32Policy, Attach.

Your AWS IoT device is now configured to have permission to connect to AWS IoT Core. It can also publish to the topic esp32/pub and subscribe to the topic esp32/sub. For more information on securing devices, see AWS IoT Policies.

Installing and configuring the Arduino IDE

The Arduino IDE is an open-source development environment for programming microcontrollers. It supports a continuously growing number of platforms including most ESP32-based modules. It must be installed along with the ESP32 board definitions, MQTT library, and ArduinoJson library.

  1. Download the Arduino installer for the desired operating system.
  2. Start Arduino and open the Preferences window.
  3. For Additional Board Manager URLs, add
  4. Choose Tools, Board, Boards Manager.
  5. Search esp32 and install the latest version.
  6. Choose Sketch, Include Library, Manage Libraries.
  7. Search MQTT, and install the latest version by Joel Gaehwiler.
  8. Repeat the library installation process for ArduinoJson.

The Arduino IDE is now installed and configured with all the board definitions and libraries needed for this walkthrough.

Configuring and flashing an ESP32 IoT device

A collection of various ESP32 development boards.

A collection of various ESP32 development boards.

For this section, you need an ESP32 device. To check if your board is compatible with the Arduino IDE, see the boards.txt file. The following code connects to AWS IoT Core securely using MQTT, a publish and subscribe messaging protocol.

This project has been tested on the following devices:

  1. Install the required serial drivers for your device. Some boards use different USB/FTDI chips for interfacing. Here are the most commonly used with links to drivers.
  2. Open the Arduino IDE and choose File, New to create a new sketch.
  3. Add a new tab and name it secrets.h.
  4. Paste the following into the secrets file.
    #include <pgmspace.h>
    #define SECRET
    #define THINGNAME ""
    const char WIFI_SSID[] = "";
    const char WIFI_PASSWORD[] = "";
    const char AWS_IOT_ENDPOINT[] = "xxxxx.amazonaws.com";
    // Amazon Root CA 1
    static const char AWS_CERT_CA[] PROGMEM = R"EOF(
    -----END CERTIFICATE-----
    // Device Certificate
    static const char AWS_CERT_CRT[] PROGMEM = R"KEY(
    -----END CERTIFICATE-----
    // Device Private Key
    static const char AWS_CERT_PRIVATE[] PROGMEM = R"KEY(
    -----END RSA PRIVATE KEY-----
  5. Enter the name of your AWS IoT thing, as it is in the console, in the field THINGNAME.
  6. To connect to Wi-Fi, add the SSID and PASSWORD of the desired network. Note: The network name should not include spaces or special characters.
  7. The AWS_IOT_ENDPOINT can be found from the Settings page in the AWS IoT console.
  8. Copy the Amazon Root CA 1, Device Certificate, and Device Private Key to their respective locations in the secrets.h file.
  9. Choose the tab for the main sketch file, and paste the following.
    #include "secrets.h"
    #include <WiFiClientSecure.h>
    #include <MQTTClient.h>
    #include <ArduinoJson.h>
    #include "WiFi.h"
    // The MQTT topics that this device should publish/subscribe
    #define AWS_IOT_PUBLISH_TOPIC   "esp32/pub"
    #define AWS_IOT_SUBSCRIBE_TOPIC "esp32/sub"
    WiFiClientSecure net = WiFiClientSecure();
    MQTTClient client = MQTTClient(256);
    void connectAWS()
      Serial.println("Connecting to Wi-Fi");
      while (WiFi.status() != WL_CONNECTED){
      // Configure WiFiClientSecure to use the AWS IoT device credentials
      // Connect to the MQTT broker on the AWS endpoint we defined earlier
      client.begin(AWS_IOT_ENDPOINT, 8883, net);
      // Create a message handler
      Serial.print("Connecting to AWS IOT");
      while (!client.connect(THINGNAME)) {
        Serial.println("AWS IoT Timeout!");
      // Subscribe to a topic
      Serial.println("AWS IoT Connected!");
    void publishMessage()
      StaticJsonDocument<200> doc;
      doc["time"] = millis();
      doc["sensor_a0"] = analogRead(0);
      char jsonBuffer[512];
      serializeJson(doc, jsonBuffer); // print to client
      client.publish(AWS_IOT_PUBLISH_TOPIC, jsonBuffer);
    void messageHandler(String &topic, String &payload) {
      Serial.println("incoming: " + topic + " - " + payload);
    //  StaticJsonDocument<200> doc;
    //  deserializeJson(doc, payload);
    //  const char* message = doc["message"];
    void setup() {
    void loop() {
  10. Choose File, Save, and give your project a name.

Flashing the ESP32

  1. Plug the ESP32 board into a USB port on the computer running the Arduino IDE.
  2. Choose Tools, Board, and then select the matching type of ESP32 module. In this case, a Sparkfun ESP32 Thing was used.
  3. Choose Tools, Port, and then select the matching port for your device.
  4. Choose Upload. Arduino reads Done uploading when the upload is successful.
  5. Choose the magnifying lens icon to open the Serial Monitor. Set the baud rate to 9600.

Keep the Serial Monitor open. When connected to Wi-Fi and then AWS IoT Core, any messages received on the topic esp32/sub are logged to this console. The device is also now publishing to the topic esp32/pub.

The topics are set at the top of the sketch. When changing or adding topics, remember to add permissions in the device policy.

// The MQTT topics that this device should publish/subscribe
#define AWS_IOT_PUBLISH_TOPIC   "esp32/pub"
#define AWS_IOT_SUBSCRIBE_TOPIC "esp32/sub"

Within this sketch, the relevant functions are publishMessage() and messageHandler().

The publishMessage() function creates a JSON object with the current time in milliseconds and the analog value of pin A0 on the device. It then publishes this JSON object to the topic esp32/pub.

void publishMessage()
  StaticJsonDocument<200> doc;
  doc["time"] = millis();
  doc["sensor_a0"] = analogRead(0);
  char jsonBuffer[512];
  serializeJson(doc, jsonBuffer); // print to client

  client.publish(AWS_IOT_PUBLISH_TOPIC, jsonBuffer);

The messageHandler() function prints out the topic and payload of any message from a subscribed topic. To see all the ways to parse JSON messages in Arduino, see the deserializeJson() example.

void messageHandler(String &topic, String &payload) {
  Serial.println("incoming: " + topic + " - " + payload);

//  StaticJsonDocument<200> doc;
//  deserializeJson(doc, payload);
//  const char* message = doc["message"];

Additional topic subscriptions can be added within the connectAWS() function by adding another line similar to the following.

// Subscribe to a topic

  Serial.println("AWS IoT Connected!");

Deploying the lambda-iot-rule AWS SAR application

Now that an ESP32 device has been connected to AWS IoT, the following steps walk through deploying an AWS Serverless Application Repository application. This is a base for building serverless integration with a physical device.

  1. On the lambda-iot-rule AWS Serverless Application Repository application page, make sure that the Region is the same as the AWS IoT device.
  2. Choose Deploy.
  3. Under Application settings, for PublishTopic, enter esp32/sub. This is the topic to which the ESP32 device is subscribed. It receives messages published to this topic. Likewise, set SubscribeTopic to esp32/pub, the topic on which the device publishes.
  4. Choose Deploy.
  5. When creation of the application is complete, choose Test app to navigate to the application page. Keep this page open for the next section.

Monitoring and testing

At this stage, two Lambda functions, a DynamoDB table, and an AWS IoT rule have been deployed. The IoT rule forwards messages on topic esp32/pub to TopicSubscriber, a Lambda function, which inserts the messages on to the DynamoDB table.

  1. On the application page, under Resources, choose MyTable. This is the DynamoDB table that the TopicSubscriber Lambda function updates.
  2. Choose Items. If the ESP32 device is still active and connected, messages that it has published appear here.

The TopicPublisher Lambda function is invoked by the API Gateway endpoint and publishes to the AWS IoT topic esp32/sub.

1.     On the application page, find the Application endpoint.

2.     To test that the TopicPublisher function is working, enter the following into a terminal or command-line utility, replacing ENDPOINT with the URL from above.

curl -d '{"text":"Hello world!"}' -H "Content-Type: application/json" -X POST https://ENDPOINT/publish

Upon success, the request returns a copy of the message.

Back in the Serial Monitor, the message published to the topic esp32/sub prints out.

Creating an IoT thermal printer

With the completion of the previous steps, the ESP32 device currently logs incoming messages to the serial console.

The following steps demonstrate how the code can be modified to use incoming messages to interact with a peripheral component. This is done by wiring a thermal printer to the ESP32 in order to physically print messages. The REST endpoint from the previous section can be used as a webhook in third-party applications to interact with this device.

A wiring diagram depicting an ESP32 connected to a thermal printer.

A wiring diagram depicting an ESP32 connected to a thermal printer.

  1. Follow the product instructions for powering, wiring, and installing the correct Arduino library.
  2. Ensure that the thermal printer is working by holding the power button on the printer while connecting the power. A sample receipt prints. On that receipt, the default baud rate is specified as either 9600 or 19200.
  3. In the Arduino code from earlier, include the following lines at the top of the main sketch file. The second line defines what interface the thermal printer is connected to. &Serial2 is used to set the third hardware serial interface on the ESP32. For this example, the pins on the Sparkfun ESP32 Thing, GPIO16/GPIO17, are used for RX/TX respectively.
    #include "Adafruit_Thermal.h"
    Adafruit_Thermal printer(&Serial2);
  4. Replace the setup() function with the following to initialize the printer on device bootup. Change the baud rate of Serial2.begin() to match what is specified in the test print. The default is 19200.
    void setup() {
      // Start the thermal printer
  5. Replace the messageHandler() function with the following. On any incoming message, it parses the JSON and prints the message on the thermal printer.
    void messageHandler(String &topic, String &payload) {
      Serial.println("incoming: " + topic + " - " + payload);
      // deserialize json
      StaticJsonDocument<200> doc;
      deserializeJson(doc, payload);
      String message = doc["message"];
      // Print the message on the thermal printer
  6. Choose Upload.
  7. After the firmware has successfully uploaded, open the Serial Monitor to confirm that the board has connected to AWS IoT.
  8. Enter the following into a command-line utility, replacing ENDPOINT, as in the previous section.
    curl -d '{"message": "Hello World!"}' -H "Content-Type: application/json" -X POST https://ENDPOINT/publish

If successful, the device prints out the message “Hello World” from the attached thermal printer. This is a fully serverless IoT printer that can be triggered remotely from a webhook. As an example, this can be used with GitHub Webhooks to print a physical readout of events.


Using a simple Arduino sketch, an AWS Serverless Application Repository application, and a microcontroller, this post demonstrated how to build a basic serverless workflow for communicating with a physical device. It also showed how to expand that into an IoT thermal printer with real-world applications.

With the use of AWS serverless, advanced compute and extensibility can be added to an IoT device, from machine learning to translation services and beyond. By using the Arduino programming environment, the vast collection of open-source libraries, projects, and code examples open up a world of possibilities. The next step is to explore what can be done with an Arduino and the capabilities of AWS serverless. The sample Arduino code for this project and more can be found at this GitHub repository.

New – Machine Learning Inference at the Edge Using AWS Greengrass

Post Syndicated from Jeff Barr original https://aws.amazon.com/blogs/aws/new-machine-learning-inference-at-the-edge-using-aws-greengrass/

What happens when you combine the Internet of Things, Machine Learning, and Edge Computing? Before I tell you, let’s review each one and discuss what AWS has to offer.

Internet of Things (IoT) – Devices that connect the physical world and the digital one. The devices, often equipped with one or more types of sensors, can be found in factories, vehicles, mines, fields, homes, and so forth. Important AWS services include AWS IoT Core, AWS IoT Analytics, AWS IoT Device Management, and Amazon FreeRTOS, along with others that you can find on the AWS IoT page.

Machine Learning (ML) – Systems that can be trained using an at-scale dataset and statistical algorithms, and used to make inferences from fresh data. At Amazon we use machine learning to drive the recommendations that you see when you shop, to optimize the paths in our fulfillment centers, fly drones, and much more. We support leading open source machine learning frameworks such as TensorFlow and MXNet, and make ML accessible and easy to use through Amazon SageMaker. We also provide Amazon Rekognition for images and for video, Amazon Lex for chatbots, and a wide array of language services for text analysis, translation, speech recognition, and text to speech.

Edge Computing – The power to have compute resources and decision-making capabilities in disparate locations, often with intermittent or no connectivity to the cloud. AWS Greengrass builds on AWS IoT, giving you the ability to run Lambda functions and keep device state in sync even when not connected to the Internet.

ML Inference at the Edge
Today I would like to toss all three of these important new technologies into a blender! You can now perform Machine Learning inference at the edge using AWS Greengrass. This allows you to use the power of the AWS cloud (including fast, powerful instances equipped with GPUs) to build, train, and test your ML models before deploying them to small, low-powered, intermittently-connected IoT devices running in those factories, vehicles, mines, fields, and homes that I mentioned.

Here are a few of the many ways that you can put Greengrass ML Inference to use:

Precision Farming – With an ever-growing world population and unpredictable weather that can affect crop yields, the opportunity to use technology to increase yields is immense. Intelligent devices that are literally in the field can process images of soil, plants, pests, and crops, taking local corrective action and sending status reports to the cloud.

Physical Security – Smart devices (including the AWS DeepLens) can process images and scenes locally, looking for objects, watching for changes, and even detecting faces. When something of interest or concern arises, the device can pass the image or the video to the cloud and use Amazon Rekognition to take a closer look.

Industrial Maintenance – Smart, local monitoring can increase operational efficiency and reduce unplanned downtime. The monitors can run inference operations on power consumption, noise levels, and vibration to flag anomalies, predict failures, detect faulty equipment.

Greengrass ML Inference Overview
There are several different aspects to this new AWS feature. Let’s take a look at each one:

Machine Learning ModelsPrecompiled TensorFlow and MXNet libraries, optimized for production use on the NVIDIA Jetson TX2 and Intel Atom devices, and development use on 32-bit Raspberry Pi devices. The optimized libraries can take advantage of GPU and FPGA hardware accelerators at the edge in order to provide fast, local inferences.

Model Building and Training – The ability to use Amazon SageMaker and other cloud-based ML tools to build, train, and test your models before deploying them to your IoT devices. To learn more about SageMaker, read Amazon SageMaker – Accelerated Machine Learning.

Model Deployment – SageMaker models can (if you give them the proper IAM permissions) be referenced directly from your Greengrass groups. You can also make use of models stored in S3 buckets. You can add a new machine learning resource to a group with a couple of clicks:

These new features are available now and you can start using them today! To learn more read Perform Machine Learning Inference.



In the Works – AWS IoT Device Defender – Secure Your IoT Fleet

Post Syndicated from Jeff Barr original https://aws.amazon.com/blogs/aws/in-the-works-aws-sepio-secure-your-iot-fleet/

Scale takes on a whole new meaning when it comes to IoT. Last year I was lucky enough to tour a gigantic factory that had, on average, one environment sensor per square meter. The sensors measured temperature, humidity, and air purity several times per second, and served as an early warning system for contaminants. I’ve heard customers express interest in deploying IoT-enabled consumer devices in the millions or tens of millions.

With powerful, long-lived devices deployed in a geographically distributed fashion, managing security challenges is crucial. However, the limited amount of local compute power and memory can sometimes limit the ability to use encryption and other forms of data protection.

To address these challenges and to allow our customers to confidently deploy IoT devices at scale, we are working on IoT Device Defender. While the details might change before release, AWS IoT Device Defender is designed to offer these benefits:

Continuous AuditingAWS IoT Device Defender monitors the policies related to your devices to ensure that the desired security settings are in place. It looks for drifts away from best practices and supports custom audit rules so that you can check for conditions that are specific to your deployment. For example, you could check to see if a compromised device has subscribed to sensor data from another device. You can run audits on a schedule or on an as-needed basis.

Real-Time Detection and AlertingAWS IoT Device Defender looks for and quickly alerts you to unusual behavior that could be coming from a compromised device. It does this by monitoring the behavior of similar devices over time, looking for unauthorized access attempts, changes in connection patterns, and changes in traffic patterns (either inbound or outbound).

Fast Investigation and Mitigation – In the event that you get an alert that something unusual is happening, AWS IoT Device Defender gives you the tools, including contextual information, to help you to investigate and mitigate the problem. Device information, device statistics, diagnostic logs, and previous alerts are all at your fingertips. You have the option to reboot the device, revoke its permissions, reset it to factory defaults, or push a security fix.

Stay Tuned
I’ll have more info (and a hands-on post) as soon as possible, so stay tuned!


AWS IoT Update – Better Value with New Pricing Model

Post Syndicated from Jeff Barr original https://aws.amazon.com/blogs/aws/aws-iot-update-better-value-with-new-pricing-model/

Our customers are using AWS IoT to make their connected devices more intelligent. These devices collect & measure data in the field (below the ground, in the air, in the water, on factory floors and in hospital rooms) and use AWS IoT as their gateway to the AWS Cloud. Once connected to the cloud, customers can write device data to Amazon Simple Storage Service (S3) and Amazon DynamoDB, process data using Amazon Kinesis and AWS Lambda functions, initiate Amazon Simple Notification Service (SNS) push notifications, and much more.

New Pricing Model (20-40% Reduction)
Today we are making a change to the AWS IoT pricing model that will make it an even better value for you. Most customers will see a price reduction of 20-40%, with some receiving a significantly larger discount depending on their workload.

The original model was based on a charge for the number of messages that were sent to or from the service. This all-inclusive model was a good starting point, but also meant that some customers were effectively paying for parts of AWS IoT that they did not actually use. For example, some customers have devices that ping AWS IoT very frequently, with sparse rule sets that fire infrequently. Our new model is more fine-grained, with independent charges for each component (all prices are for devices that connect to the US East (Northern Virginia) Region):

Connectivity – Metered in 1 minute increments and based on the total time your devices are connected to AWS IoT. Priced at $0.08 per million minutes of connection (equivalent to $0.042 per device per year for 24/7 connectivity). Your devices can send keep-alive pings at 30 second to 20 minute intervals at no additional cost.

Messaging – Metered by the number of messages transmitted between your devices and AWS IoT. Pricing starts at $1 per million messages, with volume pricing falling as low as $0.70 per million. You may send and receive messages up to 128 kilobytes in size. Messages are metered in 5 kilobyte increments (up from 512 bytes previously). For example, an 8 kilobyte message is metered as two messages.

Rules Engine – Metered for each time a rule is triggered, and for the number of actions executed within a rule, with a minimum of one action per rule. Priced at $0.15 per million rules-triggered and $0.15 per million actions-executed. Rules that process a message in excess of 5 kilobytes are metered at the next multiple of the 5 kilobyte size. For example, a rule that processes an 8 kilobyte message is metered as two rules.

Device Shadow & Registry Updates – Metered on the number of operations to access or modify Device Shadow or Registry data, priced at $1.25 per million operations. Device Shadow and Registry operations are metered in 1 kilobyte increments of the Device Shadow or Registry record size. For example, an update to a 1.5 kilobyte Shadow record is metered as two operations.

The AWS Free Tier now offers a generous allocation of connection minutes, messages, triggered rules, rules actions, Shadow, and Registry usage, enough to operate a fleet of up to 50 devices. The new prices will take effect on January 1, 2018 with no effort on your part. At that time, the updated prices will be published on the AWS IoT Pricing page.

AWS IoT at re:Invent
We have an entire IoT track at this year’s AWS re:Invent. Here is a sampling:

We also have customer-led sessions from Philips, Panasonic, Enel, and Salesforce.