Tag Archives: AWS Step Functions

Automating Amazon EBS Snapshot Management with AWS Step Functions and Amazon CloudWatch Events

Post Syndicated from Andy Katz original https://aws.amazon.com/blogs/compute/automating-amazon-ebs-snapshot-management-with-aws-step-functions-and-amazon-cloudwatch-events/

Brittany Doncaster, Solutions Architect

Business continuity is important for building mission-critical workloads on AWS. As an AWS customer, you might define recovery point objectives (RPO) and recovery time objectives (RTO) for different tier applications in your business. After the RPO and RTO requirements are defined, it is up to your architects to determine how to meet those requirements.

You probably store persistent data in Amazon EBS volumes, which live within a single Availability Zone. And, following best practices, you take snapshots of your EBS volumes to back up the data on Amazon S3, which provides 11 9’s of durability. If you are following these best practices, then you’ve probably recognized the need to manage the number of snapshots you keep for a particular EBS volume and delete older, unneeded snapshots. Doing this cleanup helps save on storage costs.

Some customers also have policies stating that backups need to be stored a certain number of miles away as part of a disaster recovery (DR) plan. To meet these requirements, customers copy their EBS snapshots to the DR region. Then, the same snapshot management and cleanup has to also be done in the DR region.

All of this snapshot management logic consists of different components. You would first tag your snapshots so you could manage them. Then, determine how many snapshots you currently have for a particular EBS volume and assess that value against a retention rule. If the number of snapshots was greater than your retention value, then you would clean up old snapshots. And finally, you might copy the latest snapshot to your DR region. All these steps are just an example of a simple snapshot management workflow. But how do you automate something like this in AWS? How do you do it without servers?

One of the most powerful AWS services released in 2016 was Amazon CloudWatch Events. It enables you to build event-driven IT automation, based on events happening within your AWS infrastructure. CloudWatch Events integrates with AWS Lambda to let you execute your custom code when one of those events occurs. However, the actions to take based on those events aren’t always composed of a single Lambda function. Instead, your business logic may consist of multiple steps (like in the case of the example snapshot management flow described earlier). And you may want to run those steps in sequence or in parallel. You may also want to have retry logic or exception handling for each step.

AWS Step Functions serves just this purpose―to help you coordinate your functions and microservices. Step Functions enables you to simplify your effort and pull the error handling, retry logic, and workflow logic out of your Lambda code. Step Functions integrates with Lambda to provide a mechanism for building complex serverless applications. Now, you can kick off a Step Functions state machine based on a CloudWatch event.

In this post, I discuss how you can target Step Functions in a CloudWatch Events rule. This allows you to have event-driven snapshot management based on snapshot completion events firing in CloudWatch Event rules.

As an example of what you could do with Step Functions and CloudWatch Events, we’ve developed a reference architecture that performs management of your EBS snapshots.

Automating EBS Snapshot Management with Step Functions

This architecture assumes that you have already set up CloudWatch Events to create the snapshots on a schedule or that you are using some other means of creating snapshots according to your needs.

This architecture covers the pieces of the workflow that need to happen after a snapshot has been created.

  • It creates a CloudWatch Events rule to invoke a Step Functions state machine execution when an EBS snapshot is created.
  • The state machine then tags the snapshot, cleans up the oldest snapshots if the number of snapshots is greater than the defined number to retain, and copies the snapshot to a DR region.
  • When the DR region snapshot copy is completed, another state machine kicks off in the DR region. The new state machine has a similar flow and uses some of the same Lambda code to clean up the oldest snapshots that are greater than the defined number to retain.
  • Also, both state machines demonstrate how you can use Step Functions to handle errors within your workflow. Any errors that are caught during execution result in the execution of a Lambda function that writes a message to an SNS topic. Therefore, if any errors occur, you can subscribe to the SNS topic and get notified.

The following is an architecture diagram of the reference architecture:

Creating the Lambda functions and Step Functions state machines

First, pull the code from GitHub and use the AWS CLI to create S3 buckets for the Lambda code in the primary and DR regions. For this example, assume that the primary region is us-west-2 and the DR region is us-east-2. Run the following commands, replacing the italicized text in <> with your own unique bucket names.

git clone https://github.com/awslabs/aws-step-functions-ebs-snapshot-mgmt.git

cd aws-step-functions-ebs-snapshot-mgmt/

aws s3 mb s3://<primary region bucket name> --region us-west-2

aws s3 mb s3://<DR region bucket name> --region us-east-2

Next, use the Serverless Application Model (SAM), which uses AWS CloudFormation to deploy the Lambda functions and Step Functions state machines in the primary and DR regions. Replace the italicized text in <> with the S3 bucket names that you created earlier.

aws cloudformation package --template-file PrimaryRegionTemplate.yaml --s3-bucket <primary region bucket name>  --output-template-file tempPrimary.yaml --region us-west-2

aws cloudformation deploy --template-file tempPrimary.yaml --stack-name ebsSnapshotMgmtPrimary --capabilities CAPABILITY_IAM --region us-west-2

aws cloudformation package --template-file DR_RegionTemplate.yaml --s3-bucket <DR region bucket name> --output-template-file tempDR.yaml  --region us-east-2

aws cloudformation deploy --template-file tempDR.yaml --stack-name ebsSnapshotMgmtDR --capabilities CAPABILITY_IAM --region us-east-2

CloudWatch event rule verification

The CloudFormation templates deploy the following resources:

  • The Lambda functions that are coordinated by Step Functions
  • The Step Functions state machine
  • The SNS topic
  • The CloudWatch Events rules that trigger the state machine execution

So, all of the CloudWatch event rules have been created for you by performing the preceding commands. The next section demonstrates how you could create the CloudWatch event rule manually. To jump straight to testing the workflow, see the “Testing in your Account” section. Otherwise, you begin by setting up the CloudWatch event rule in the primary region for the createSnapshot event and also the CloudWatch event rule in the DR region for the copySnapshot command.

First, open the CloudWatch console in the primary region.

Choose Create Rule and create a rule for the createSnapshot command, with your newly created Step Function state machine as the target.

For Event Source, choose Event Pattern and specify the following values:

  • Service Name: EC2
  • Event Type: EBS Snapshot Notification
  • Specific Event: createSnapshot

For Target, choose Step Functions state machine, then choose the state machine created by the CloudFormation commands. Choose Create a new role for this specific resource. Your completed rule should look like the following:

Choose Configure Details and give the rule a name and description.

Choose Create Rule. You now have a CloudWatch Events rule that triggers a Step Functions state machine execution when the EBS snapshot creation is complete.

Now, set up the CloudWatch Events rule in the DR region as well. This looks almost same, but is based off the copySnapshot event instead of createSnapshot.

In the upper right corner in the console, switch to your DR region. Choose CloudWatch, Create Rule.

For Event Source, choose Event Pattern and specify the following values:

  • Service Name: EC2
  • Event Type: EBS Snapshot Notification
  • Specific Event: copySnapshot

For Target, choose Step Functions state machine, then select the state machine created by the CloudFormation commands. Choose Create a new role for this specific resource. Your completed rule should look like in the following:

As in the primary region, choose Configure Details and then give this rule a name and description. Complete the creation of the rule.

Testing in your account

To test this setup, open the EC2 console and choose Volumes. Select a volume to snapshot. Choose Actions, Create Snapshot, and then create a snapshot.

This results in a new execution of your state machine in the primary and DR regions. You can view these executions by going to the Step Functions console and selecting your state machine.

From there, you can see the execution of the state machine.

Primary region state machine:

DR region state machine:

I’ve also provided CloudFormation templates that perform all the earlier setup without using git clone and running the CloudFormation commands. Choose the Launch Stack buttons below to launch the primary and DR region stacks in Dublin and Ohio, respectively. From there, you can pick up at the Testing in Your Account section above to finish the example. All of the code for this example architecture is located in the aws-step-functions-ebs-snapshot-mgmt AWSLabs repo.

Launch EBS Snapshot Management into Ireland with CloudFormation
Primary Region eu-west-1 (Ireland)

Launch EBS Snapshot Management into Ohio with CloudFormation
DR Region us-east-2 (Ohio)

Summary

This reference architecture is just an example of how you can use Step Functions and CloudWatch Events to build event-driven IT automation. The possibilities are endless:

  • Use this pattern to perform other common cleanup type jobs such as managing Amazon RDS snapshots, old versions of Lambda functions, or old Amazon ECR images—all triggered by scheduled events.
  • Use Trusted Advisor events to identify unused EC2 instances or EBS volumes, then coordinate actions on them, such as alerting owners, stopping, or snapshotting.

Happy coding and please let me know what useful state machines you build!

Automate Your IT Operations Using AWS Step Functions and Amazon CloudWatch Events

Post Syndicated from Andy Katz original https://aws.amazon.com/blogs/compute/automate-your-it-operations-using-aws-step-functions-and-amazon-cloudwatch-events/


Rob Percival, Associate Solutions Architect

Are you interested in reducing the operational overhead of your AWS Cloud infrastructure? One way to achieve this is to automate the response to operational events for resources in your AWS account.

Amazon CloudWatch Events provides a near real-time stream of system events that describe the changes and notifications for your AWS resources. From this stream, you can create rules to route specific events to AWS Step Functions, AWS Lambda, and other AWS services for further processing and automated actions.

In this post, learn how you can use Step Functions to orchestrate serverless IT automation workflows in response to CloudWatch events sourced from AWS Health, a service that monitors and generates events for your AWS resources. As a real-world example, I show automating the response to a scenario where an IAM user access key has been exposed.

Serverless workflows with Step Functions and Lambda

Step Functions makes it easy to develop and orchestrate components of operational response automation using visual workflows. Building automation workflows from individual Lambda functions that perform discrete tasks lets you develop, test, and modify the components of your workflow quickly and seamlessly. As serverless services, Step Functions and Lambda also provide the benefits of more productive development, reduced operational overhead, and no costs incurred outside of when the workflows are actively executing.

Example workflow

As an example, this post focuses on automating the response to an event generated by AWS Health when an IAM access key has been publicly exposed on GitHub. This is a diagram of the automation workflow:

AWS proactively monitors popular code repository sites for IAM access keys that have been publicly exposed. Upon detection of an exposed IAM access key, AWS Health generates an AWS_RISK_CREDENTIALS_EXPOSED event in the AWS account related to the exposed key. A configured CloudWatch Events rule detects this event and invokes a Step Functions state machine. The state machine then orchestrates the automated workflow that deletes the exposed IAM access key, summarizes the recent API activity for the exposed key, and sends the summary message to an Amazon SNS topic to notify the subscribers―in that order.

The corresponding Step Functions state machine diagram of this automation workflow can be seen below:

While this particular example focuses on IT automation workflows in response to the AWS_RISK_CREDENTIALS_EXPOSEDevent sourced from AWS Health, it can be generalized to integrate with other events from these services, other event-generating AWS services, and even run on a time-based schedule.

Walkthrough

To follow along, use the code and resources found in the aws-health-tools GitHub repo. The code and resources include an AWS CloudFormation template, in addition to instructions on how to use it.

Launch Stack into N. Virginia with CloudFormation

The Step Functions state machine execution starts with the exposed keys event details in JSON, a sanitized example of which is provided below:

{
    "version": "0",
    "id": "121345678-1234-1234-1234-123456789012",
    "detail-type": "AWS Health Event",
    "source": "aws.health",
    "account": "123456789012",
    "time": "2016-06-05T06:27:57Z",
    "region": "us-east-1",
    "resources": [],
    "detail": {
        "eventArn": "arn:aws:health:us-east-1::event/AWS_RISK_CREDENTIALS_EXPOSED_XXXXXXXXXXXXXXXXX",
        "service": "RISK",
        "eventTypeCode": "AWS_RISK_CREDENTIALS_EXPOSED",
        "eventTypeCategory": "issue",
        "startTime": "Sat, 05 Jun 2016 15:10:09 GMT",
        "eventDescription": [
            {
                "language": "en_US",
                "latestDescription": "A description of the event is provided here"
            }
        ],
        "affectedEntities": [
            {
                "entityValue": "ACCESS_KEY_ID_HERE"
            }
        ]
    }
}

After it’s invoked, the state machine execution proceeds as follows.

Step 1: Delete the exposed IAM access key pair

The first thing you want to do when you determine that an IAM access key has been exposed is to delete the key pair so that it can no longer be used to make API calls. This Step Functions task state deletes the exposed access key pair detailed in the incoming event, and retrieves the IAM user associated with the key to look up API activity for the user in the next step. The user name, access key, and other details about the event are passed to the next step as JSON.

This state contains a powerful error-handling feature offered by Step Functions task states called a catch configuration. Catch configurations allow you to reroute and continue state machine invocation at new states depending on potential errors that occur in your task function. In this case, the catch configuration skips to Step 3. It immediately notifies your security team that errors were raised in the task function of this step (Step 1), when attempting to look up the corresponding IAM user for a key or delete the user’s access key.

Note: Step Functions also offers a retry configuration for when you would rather retry a task function that failed due to error, with the option to specify an increasing time interval between attempts and a maximum number of attempts.

Step 2: Summarize recent API activity for key

After you have deleted the access key pair, you’ll want to have some immediate insight into whether it was used for malicious activity in your account. Another task state, this step uses AWS CloudTrail to look up and summarize the most recent API activity for the IAM user associated with the exposed key. The summary is in the form of counts for each API call made and resource type and name affected. This summary information is then passed to the next step as JSON. This step requires information that you obtained in Step 1. Step Functions ensures the successful completion of Step 1 before moving to Step 2.

Step 3: Notify security

The summary information gathered in the last step can provide immediate insight into any malicious activity on your account made by the exposed key. To determine this and further secure your account if necessary, you must notify your security team with the gathered summary information.

This final task state generates an email message providing in-depth detail about the event using the API activity summary, and publishes the message to an SNS topic subscribed to by the members of your security team.

If the catch configuration of the task state in Step 1 was triggered, then the security notification email instead directs your security team to log in to the console and navigate to the Personal Health Dashboard to view more details on the incident.

Lessons learned

When implementing this use case with Step Functions and Lambda, consider the following:

  • One of the most important parts of implementing automation in response to operational events is to ensure visibility into the response and resolution actions is retained. Step Functions and Lambda enable you to orchestrate your granular response and resolution actions that provides direct visibility into the state of the automation workflow.
  • This basic workflow currently executes these steps serially with a catch configuration for error handling. More sophisticated workflows can leverage the parallel execution, branching logic, and time delay functionality provided by Step Functions.
  • Catch and retry configurations for task states allow for orchestrating reliable workflows while maintaining the granularity of each Lambda function. Without leveraging a catch configuration in Step 1, you would have had to duplicate code from the function in Step 3 to ensure that your security team was notified on failure to delete the access key.
  • Step Functions and Lambda are serverless services, so there is no cost for these services when they are not running. Because this IT automation workflow only runs when an IAM access key is exposed for this account (which is hopefully rare!), the total monthly cost for this workflow is essentially $0.

Conclusion

Automating the response to operational events for resources in your AWS account can free up the valuable time of your engineers. Step Functions and Lambda enable granular IT automation workflows to achieve this result while gaining direct visibility into the orchestration and state of the automation.

For more examples of how to use Step Functions to automate the operations of your AWS resources, or if you’d like to see how Step Functions can be used to build and orchestrate serverless applications, visit Getting Started on the Step Functions website.

Synchronizing Amazon S3 Buckets Using AWS Step Functions

Post Syndicated from Andy Katz original https://aws.amazon.com/blogs/compute/synchronizing-amazon-s3-buckets-using-aws-step-functions/

Constantin Gonzalez is a Principal Solutions Architect at AWS

In my free time, I run a small blog that uses Amazon S3 to host static content and Amazon CloudFront to distribute it world-wide. I use a home-grown, static website generator to create and upload my blog content onto S3.

My blog uses two S3 buckets: one for staging and testing, and one for production. As a website owner, I want to update the production bucket with all changes from the staging bucket in a reliable and efficient way, without having to create and populate a new bucket from scratch. Therefore, to synchronize files between these two buckets, I use AWS Lambda and AWS Step Functions.

In this post, I show how you can use Step Functions to build a scalable synchronization engine for S3 buckets and learn some common patterns for designing Step Functions state machines while you do so.

Step Functions overview

Step Functions makes it easy to coordinate the components of distributed applications and microservices using visual workflows. Building applications from individual components that each perform a discrete function lets you scale and change applications quickly.

While this particular example focuses on synchronizing objects between two S3 buckets, it can be generalized to any other use case that involves coordinated processing of any number of objects in S3 buckets, or other, similar data processing patterns.

Bucket replication options

Before I dive into the details on how this particular example works, take a look at some alternatives for copying or replicating data between two Amazon S3 buckets:

  • The AWS CLI provides customers with a powerful aws s3 sync command that can synchronize the contents of one bucket with another.
  • S3DistCP is a powerful tool for users of Amazon EMR that can efficiently load, save, or copy large amounts of data between S3 buckets and HDFS.
  • The S3 cross-region replication functionality enables automatic, asynchronous copying of objects across buckets in different AWS regions.

In this use case, you are looking for a slightly different bucket synchronization solution that:

  • Works within the same region
  • Is more scalable than a CLI approach running on a single machine
  • Doesn’t require managing any servers
  • Uses a more finely grained cost model than the hourly based Amazon EMR approach

You need a scalable, serverless, and customizable bucket synchronization utility.

Solution architecture

Your solution needs to do three things:

  1. Copy all objects from a source bucket into a destination bucket, but leave out objects that are already present, for efficiency.
  2. Delete all "orphaned" objects from the destination bucket that aren’t present on the source bucket, because you don’t want obsolete objects lying around.
  3. Keep track of all objects for #1 and #2, regardless of how many objects there are.

In the beginning, you read in the source and destination buckets as parameters and perform basic parameter validation. Then, you operate two separate, independent loops, one for copying missing objects and one for deleting obsolete objects. Each loop is a sequence of Step Functions states that read in chunks of S3 object lists and use the continuation token to decide in a choice state whether to continue the loop or not.

This solution is based on the following architecture that uses Step Functions, Lambda, and two S3 buckets:

As you can see, this setup involves no servers, just two main building blocks:

  • Step Functions manages the overall flow of synchronizing the objects from the source bucket with the destination bucket.
  • A set of Lambda functions carry out the individual steps necessary to perform the work, such as validating input, getting lists of objects from source and destination buckets, copying or deleting objects in batches, and so on.

To understand the synchronization flow in more detail, look at the Step Functions state machine diagram for this example.

Walkthrough

Here’s a detailed discussion of how this works.

To follow along, use the code in the sync-buckets-state-machine GitHub repo. The code comes with a ready-to-run deployment script in Python that takes care of all the IAM roles, policies, Lambda functions, and of course the Step Functions state machine deployment using AWS CloudFormation, as well as instructions on how to use it.

Fine print: Use at your own risk

Before I start, here are some disclaimers:

  • Educational purposes only.

    The following example and code are intended for educational purposes only. Make sure that you customize, test, and review it on your own before using any of this in production.

  • S3 object deletion.

    In particular, using the code included below may delete objects on S3 in order to perform synchronization. Make sure that you have backups of your data. In particular, consider using the Amazon S3 Versioning feature to protect yourself against unintended data modification or deletion.

Step Functions execution starts with an initial set of parameters that contain the source and destination bucket names in JSON:

{
    "source":       "my-source-bucket-name",
    "destination":  "my-destination-bucket-name"
}

Armed with this data, Step Functions execution proceeds as follows.

Step 1: Detect the bucket region

First, you need to know the regions where your buckets reside. In this case, take advantage of the Step Functions Parallel state. This allows you to use a Lambda function get_bucket_location.py inside two different, parallel branches of task states:

  • FindRegionForSourceBucket
  • FindRegionForDestinationBucket

Each task state receives one bucket name as an input parameter, then detects the region corresponding to "their" bucket. The output of these functions is collected in a result array containing one element per parallel function.

Step 2: Combine the parallel states

The output of a parallel state is a list with all the individual branches’ outputs. To combine them into a single structure, use a Lambda function called combine_dicts.py in its own CombineRegionOutputs task state. The function combines the two outputs from step 1 into a single JSON dict that provides you with the necessary region information for each bucket.

Step 3: Validate the input

In this walkthrough, you only support buckets that reside in the same region, so you need to decide if the input is valid or if the user has given you two buckets in different regions. To find out, use a Lambda function called validate_input.py in the ValidateInput task state that tests if the two regions from the previous step are equal. The output is a Boolean.

Step 4: Branch the workflow

Use another type of Step Functions state, a Choice state, which branches into a Failure state if the comparison in step 3 yields false, or proceeds with the remaining steps if the comparison was successful.

Step 5: Execute in parallel

The actual work is happening in another Parallel state. Both branches of this state are very similar to each other and they re-use some of the Lambda function code.

Each parallel branch implements a looping pattern across the following steps:

  1. Use a Pass state to inject either the string value "source" (InjectSourceBucket) or "destination" (InjectDestinationBucket) into the listBucket attribute of the state document.

    The next step uses either the source or the destination bucket, depending on the branch, while executing the same, generic Lambda function. You don’t need two Lambda functions that differ only slightly. This step illustrates how to use Pass states as a way of injecting constant parameters into your state machine and as a way of controlling step behavior while re-using common step execution code.

  2. The next step UpdateSourceKeyList/UpdateDestinationKeyList lists objects in the given bucket.

    Remember that the previous step injected either "source" or "destination" into the state document’s listBucket attribute. This step uses the same list_bucket.py Lambda function to list objects in an S3 bucket. The listBucket attribute of its input decides which bucket to list. In the left branch of the main parallel state, use the list of source objects to work through copying missing objects. The right branch uses the list of destination objects, to check if they have a corresponding object in the source bucket and eliminate any orphaned objects. Orphans don’t have a source object of the same S3 key.

  3. This step performs the actual work. In the left branch, the CopySourceKeys step uses the copy_keys.py Lambda function to go through the list of source objects provided by the previous step, then copies any missing object into the destination bucket. Its sister step in the other branch, DeleteOrphanedKeys, uses its destination bucket key list to test whether each object from the destination bucket has a corresponding source object, then deletes any orphaned objects.

  4. The S3 ListObjects API action is designed to be scalable across many objects in a bucket. Therefore, it returns object lists in chunks of configurable size, along with a continuation token. If the API result has a continuation token, it means that there are more objects in this list. You can work from token to token to continue getting object list chunks, until you get no more continuation tokens.

By breaking down large amounts of work into chunks, you can make sure each chunk is completed within the timeframe allocated for the Lambda function, and within the maximum input/output data size for a Step Functions state.

This approach comes with a slight tradeoff: the more objects you process at one time in a given chunk, the faster you are done. There’s less overhead for managing individual chunks. On the other hand, if you process too many objects within the same chunk, you risk going over time and space limits of the processing Lambda function or the Step Functions state so the work cannot be completed.

In this particular case, use a Lambda function that maximizes the number of objects listed from the S3 bucket that can be stored in the input/output state data. This is currently up to 32,768 bytes, assuming (based on some experimentation) that the execution of the COPY/DELETE requests in the processing states can always complete in time.

A more sophisticated approach would use the Step Functions retry/catch state attributes to account for any time limits encountered and adjust the list size accordingly through some list site adjusting.

Step 6: Test for completion

Because the presence of a continuation token in the S3 ListObjects output signals that you are not done processing all objects yet, use a Choice state to test for its presence. If a continuation token exists, it branches into the UpdateSourceKeyList step, which uses the token to get to the next chunk of objects. If there is no token, you’re done. The state machine then branches into the FinishCopyBranch/FinishDeleteBranch state.

By using Choice states like this, you can create loops exactly like the old times, when you didn’t have for statements and used branches in assembly code instead!

Step 7: Success!

Finally, you’re done, and can step into your final Success state.

Lessons learned

When implementing this use case with Step Functions and Lambda, I learned the following things:

  • Sometimes, it is necessary to manipulate the JSON state of a Step Functions state machine with just a few lines of code that hardly seem to warrant their own Lambda function. This is ok, and the cost is actually pretty low given Lambda’s 100 millisecond billing granularity. The upside is that functions like these can be helpful to make the data more palatable for the following steps or for facilitating Choice states. An example here would be the combine_dicts.py function.
  • Pass states can be useful beyond debugging and tracing, they can be used to inject arbitrary values into your state JSON and guide generic Lambda functions into doing specific things.
  • Choice states are your friend because you can build while-loops with them. This allows you to reliably grind through large amounts of data with the patience of an engine that currently supports execution times of up to 1 year.

    Currently, there is an execution history limit of 25,000 events. Each Lambda task state execution takes up 5 events, while each choice state takes 2 events for a total of 7 events per loop. This means you can loop about 3500 times with this state machine. For even more scalability, you can split up work across multiple Step Functions executions through object key sharding or similar approaches.

  • It’s not necessary to spend a lot of time coding exception handling within your Lambda functions. You can delegate all exception handling to Step Functions and instead simplify your functions as much as possible.

  • Step Functions are great replacements for shell scripts. This could have been a shell script, but then I would have had to worry about where to execute it reliably, how to scale it if it went beyond a few thousand objects, etc. Think of Step Functions and Lambda as tools for scripting at a cloud level, beyond the boundaries of servers or containers. "Serverless" here also means "boundary-less".

Summary

This approach gives you scalability by breaking down any number of S3 objects into chunks, then using Step Functions to control logic to work through these objects in a scalable, serverless, and fully managed way.

To take a look at the code or tweak it for your own needs, use the code in the sync-buckets-state-machine GitHub repo.

To see more examples, please visit the Step Functions Getting Started page.

Enjoy!

Event: AWS Serverless Roadshow – Hands-on Workshops

Post Syndicated from Tara Walker original https://aws.amazon.com/blogs/aws/event-aws-serverless-roadshow-hands-on-workshops/

Surely, some of you have contemplated how you would survive the possible Zombie apocalypse or how you would build your exciting new startup to disrupt the transportation industry when Unicorn haven is uncovered. Well, there is no need to worry; I know just the thing to get you prepared to handle both of those scenarios: the AWS Serverless Computing Workshop Roadshow.

With the roadshow’s serverless workshops, you can get hands-on experience building serverless applications and microservices so you can rebuild what remains of our great civilization after a widespread viral infection causes human corpses to reanimate around the world in the AWS Zombie Microservices Workshop. In addition, you can give your startup a jump on the competition with the Wild Rydes workshop in order to revolutionize the transportation industry; just in time for a pilot’s crash landing leading the way to the discovery of abundant Unicorn pastures found on the outskirts of the female Amazonian warrior inhabited island of Themyscira also known as Paradise Island.

These free, guided hands-on workshops will introduce the basics of building serverless applications and microservices for common and uncommon scenarios using services like AWS Lambda, Amazon API Gateway, Amazon DynamoDB, Amazon S3, Amazon Kinesis, AWS Step Functions, and more. Let me share some advice before you decide to tackle Zombies and mount Unicorns – don’t forget to bring your laptop to the workshop and make sure you have an AWS account established and available for use for the event.

Check out the schedule below and get prepared today by registering for an upcoming workshop in a city near you. Remember these are workshops are completely free, so participation is on a first come, first served basis. So register and get there early, we need Zombie hunters and Unicorn riders across the globe.  Learn more about AWS Serverless Computing Workshops here and register for your city using links below.

Event Location Date
Wild Rydes New York Thursday, June 8
Wild Rydes Austin Thursday, June 22
Wild Rydes Santa Monica Thursday, July 20
Zombie Apocalypse Chicago Thursday, July 20
Wild Rydes Atlanta Tuesday, September 12
Zombie Apocalypse Dallas Tuesday, September 19

 

I look forward to fighting zombies and riding unicorns with you all.

Tara

Building High-Throughput Genomics Batch Workflows on AWS: Workflow Layer (Part 4 of 4)

Post Syndicated from Andy Katz original https://aws.amazon.com/blogs/compute/building-high-throughput-genomics-batch-workflows-on-aws-workflow-layer-part-4-of-4/

Aaron Friedman is a Healthcare and Life Sciences Partner Solutions Architect at AWS

Angel Pizarro is a Scientific Computing Technical Business Development Manager at AWS

This post is the fourth in a series on how to build a genomics workflow on AWS. In Part 1, we introduced a general architecture, shown below, and highlighted the three common layers in a batch workflow:

  • Job
  • Batch
  • Workflow

In Part 2, you built a Docker container for each job that needed to run as part of your workflow, and stored them in Amazon ECR.

In Part 3, you tackled the batch layer and built a scalable, elastic, and easily maintainable batch engine using AWS Batch. This solution took care of dynamically scaling your compute resources in response to the number of runnable jobs in your job queue length as well as managed job placement.

In part 4, you build out the workflow layer of your solution using AWS Step Functions and AWS Lambda. You then run an end-to-end genomic analysis―specifically known as exome secondary analysis―for many times at a cost of less than $1 per exome.

Step Functions makes it easy to coordinate the components of your applications using visual workflows. Building applications from individual components that each perform a single function lets you scale and change your workflow quickly. You can use the graphical console to arrange and visualize the components of your application as a series of steps, which simplify building and running multi-step applications. You can change and add steps without writing code, so you can easily evolve your application and innovate faster.

An added benefit of using Step Functions to define your workflows is that the state machines you create are immutable. While you can delete a state machine, you cannot alter it after it is created. For regulated workloads where auditing is important, you can be assured that state machines you used in production cannot be altered.

In this blog post, you will create a Lambda state machine to orchestrate your batch workflow. For more information on how to create a basic state machine, please see this Step Functions tutorial.

All code related to this blog series can be found in the associated GitHub repository here.

Build a state machine building block

To skip the following steps, we have provided an AWS CloudFormation template that can deploy your Step Functions state machine. You can use this in combination with the setup you did in part 3 to quickly set up the environment in which to run your analysis.

The state machine is composed of smaller state machines that submit a job to AWS Batch, and then poll and check its execution.

The steps in this building block state machine are as follows:

  1. A job is submitted.
    Each analytical module/job has its own Lambda function for submission and calls the batchSubmitJob Lambda function that you built in the previous blog post. You will build these specialized Lambda functions in the following section.
  2. The state machine queries the AWS Batch API for the job status.
    This is also a Lambda function.
  3. The job status is checked to see if the job has completed.
    If the job status equals SUCCESS, proceed to log the final job status. If the job status equals FAILED, end the execution of the state machine. In all other cases, wait 30 seconds and go back to Step 2.

Here is the JSON representing this state machine.

{
  "Comment": "A simple example that submits a Job to AWS Batch",
  "StartAt": "SubmitJob",
  "States": {
    "SubmitJob": {
      "Type": "Task",
      "Resource": "arn:aws:lambda:us-east-1:<account-id>::function:batchSubmitJob",
      "Next": "GetJobStatus"
    },
    "GetJobStatus": {
      "Type": "Task",
      "Resource": "arn:aws:lambda:us-east-1:<account-id>:function:batchGetJobStatus",
      "Next": "CheckJobStatus",
      "InputPath": "$",
      "ResultPath": "$.status"
    },
    "CheckJobStatus": {
      "Type": "Choice",
      "Choices": [
        {
          "Variable": "$.status",
          "StringEquals": "FAILED",
          "End": true
        },
        {
          "Variable": "$.status",
          "StringEquals": "SUCCEEDED",
          "Next": "GetFinalJobStatus"
        }
      ],
      "Default": "Wait30Seconds"
    },
    "Wait30Seconds": {
      "Type": "Wait",
      "Seconds": 30,
      "Next": "GetJobStatus"
    },
    "GetFinalJobStatus": {
      "Type": "Task",
      "Resource": "arn:aws:lambda:us-east-1:<account-id>:function:batchGetJobStatus",
      "End": true
    }
  }
}

Building the Lambda functions for the state machine

You need two basic Lambda functions for this state machine. The first one submits a job to AWS Batch and the second checks the status of the AWS Batch job that was submitted.

In AWS Step Functions, you specify an input as JSON that is read into your state machine. Each state receives the aggregate of the steps immediately preceding it, and you can specify which components a state passes on to its children. Because you are using Lambda functions to execute tasks, one of the easiest routes to take is to modify the input JSON, represented as a Python dictionary, within the Lambda function and return the entire dictionary back for the next state to consume.

Building the batchSubmitIsaacJob Lambda function

For Step 1 above, you need a Lambda function for each of the steps in your analysis workflow. As you created a generic Lambda function in the previous post to submit a batch job (batchSubmitJob), you can use that function as the basis for the specialized functions you’ll include in this state machine. Here is such a Lambda function for the Isaac aligner.

from __future__ import print_function

import boto3
import json
import traceback

lambda_client = boto3.client('lambda')



def lambda_handler(event, context):
    try:
        # Generate output put
        bam_s3_path = '/'.join([event['resultsS3Path'], event['sampleId'], 'bam/'])

        depends_on = event['dependsOn'] if 'dependsOn' in event else []

        # Generate run command
        command = [
            '--bam_s3_folder_path', bam_s3_path,
            '--fastq1_s3_path', event['fastq1S3Path'],
            '--fastq2_s3_path', event['fastq2S3Path'],
            '--reference_s3_path', event['isaac']['referenceS3Path'],
            '--working_dir', event['workingDir']
        ]

        if 'cmdArgs' in event['isaac']:
            command.extend(['--cmd_args', event['isaac']['cmdArgs']])
        if 'memory' in event['isaac']:
            command.extend(['--memory', event['isaac']['memory']])

        # Submit Payload
        response = lambda_client.invoke(
            FunctionName='batchSubmitJob',
            InvocationType='RequestResponse',
            LogType='Tail',
            Payload=json.dumps(dict(
                dependsOn=depends_on,
                containerOverrides={
                    'command': command,
                },
                jobDefinition=event['isaac']['jobDefinition'],
                jobName='-'.join(['isaac', event['sampleId']]),
                jobQueue=event['isaac']['jobQueue']
            )))

        response_payload = response['Payload'].read()

        # Update event
        event['bamS3Path'] = bam_s3_path
        event['jobId'] = json.loads(response_payload)['jobId']
        
        return event
    except Exception as e:
        traceback.print_exc()
        raise e

In the Lambda console, create a Python 2.7 Lambda function named batchSubmitIsaacJob and paste in the above code. Use the LambdaBatchExecutionRole that you created in the previous post. For more information, see Step 2.1: Create a Hello World Lambda Function.

This Lambda function reads in the inputs passed to the state machine it is part of, formats the data for the batchSubmitJob Lambda function, invokes that Lambda function, and then modifies the event dictionary to pass onto the subsequent states. You can repeat these for each of the other tools, which can be found in the tools//lambda/lambda_function.py script in the GitHub repo.

Building the batchGetJobStatus Lambda function

For Step 2 above, the process queries the AWS Batch DescribeJobs API action with jobId to identify the state that the job is in. You can put this into a Lambda function to integrate it with Step Functions.

In the Lambda console, create a new Python 2.7 function with the LambdaBatchExecutionRole IAM role. Name your function batchGetJobStatus and paste in the following code. This is similar to the batch-get-job-python27 Lambda blueprint.

from __future__ import print_function

import boto3
import json

print('Loading function')

batch_client = boto3.client('batch')

def lambda_handler(event, context):
    # Log the received event
    print("Received event: " + json.dumps(event, indent=2))
    # Get jobId from the event
    job_id = event['jobId']

    try:
        response = batch_client.describe_jobs(
            jobs=[job_id]
        )
        job_status = response['jobs'][0]['status']
        return job_status
    except Exception as e:
        print(e)
        message = 'Error getting Batch Job status'
        print(message)
        raise Exception(message)

Structuring state machine input

You have structured the state machine input so that general file references are included at the top-level of the JSON object, and any job-specific items are contained within a nested JSON object. At a high level, this is what the input structure looks like:

{
        "general_field_1": "value1",
        "general_field_2": "value2",
        "general_field_3": "value3",
        "job1": {},
        "job2": {},
        "job3": {}
}

Building the full state machine

By chaining these state machine components together, you can quickly build flexible workflows that can process genomes in multiple ways. The development of the larger state machine that defines the entire workflow uses four of the above building blocks. You use the Lambda functions that you built in the previous section. Rename each building block submission to match the tool name.

We have provided a CloudFormation template to deploy your state machine and the associated IAM roles. In the CloudFormation console, select Create Stack, choose your template (deploy_state_machine.yaml), and enter in the ARNs for the Lambda functions you created.

Continue through the rest of the steps and deploy your stack. Be sure to check the box next to "I acknowledge that AWS CloudFormation might create IAM resources."

Once the CloudFormation stack is finished deploying, you should see the following image of your state machine.

In short, you first submit a job for Isaac, which is the aligner you are using for the analysis. Next, you use parallel state to split your output from "GetFinalIsaacJobStatus" and send it to both your variant calling step, Strelka, and your QC step, Samtools Stats. These then are run in parallel and you annotate the results from your Strelka step with snpEff.

Putting it all together

Now that you have built all of the components for a genomics secondary analysis workflow, test the entire process.

We have provided sequences from an Illumina sequencer that cover a region of the genome known as the exome. Most of the positions in the genome that we have currently associated with disease or human traits reside in this region, which is 1–2% of the entire genome. The workflow that you have built works for both analyzing an exome, as well as an entire genome.

Additionally, we have provided prebuilt reference genomes for Isaac, located at:

s3://aws-batch-genomics-resources/reference/

If you are interested, we have provided a script that sets up all of that data. To execute that script, run the following command on a large EC2 instance:

make reference REGISTRY=<your-ecr-registry>

Indexing and preparing this reference takes many hours on a large-memory EC2 instance. Be careful about the costs involved and note that the data is available through the prebuilt reference genomes.

Starting the execution

In a previous section, you established a provenance for the JSON that is fed into your state machine. For ease, we have auto-populated the input JSON for you to the state machine. You can also find this in the GitHub repo under workflow/test.input.json:

{
  "fastq1S3Path": "s3://aws-batch-genomics-resources/fastq/SRR1919605_1.fastq.gz",
  "fastq2S3Path": "s3://aws-batch-genomics-resources/fastq/SRR1919605_2.fastq.gz",
  "referenceS3Path": "s3://aws-batch-genomics-resources/reference/hg38.fa",
  "resultsS3Path": "s3://<bucket>/genomic-workflow/results",
  "sampleId": "NA12878_states_1",
  "workingDir": "/scratch",
  "isaac": {
    "jobDefinition": "isaac-myenv:1",
    "jobQueue": "arn:aws:batch:us-east-1:<account-id>:job-queue/highPriority-myenv",
    "referenceS3Path": "s3://aws-batch-genomics-resources/reference/isaac/"
  },
  "samtoolsStats": {
    "jobDefinition": "samtools_stats-myenv:1",
    "jobQueue": "arn:aws:batch:us-east-1:<account-id>:job-queue/lowPriority-myenv"
  },
  "strelka": {
    "jobDefinition": "strelka-myenv:1",
    "jobQueue": "arn:aws:batch:us-east-1:<account-id>:job-queue/highPriority-myenv",
    "cmdArgs": " --exome "
  },
  "snpEff": {
    "jobDefinition": "snpeff-myenv:1",
    "jobQueue": "arn:aws:batch:us-east-1:<account-id>:job-queue/lowPriority-myenv",
    "cmdArgs": " -t hg38 "
  }
}

You are now at the stage to run your full genomic analysis. Copy the above to a new text file, change paths and ARNs to the ones that you created previously, and save your JSON input as input.states.json.

In the CLI, execute the following command. You need the ARN of the state machine that you created in the previous post:

aws stepfunctions start-execution --state-machine-arn <your-state-machine-arn> --input file://input.states.json

Your analysis has now started. By using Spot Instances with AWS Batch, you can quickly scale out your workflows while concurrently optimizing for cost. While this is not guaranteed, most executions of the workflows presented here should cost under $1 for a full analysis.

Monitoring the execution

The output from the above CLI command gives you the ARN that describes the specific execution. Copy that and navigate to the Step Functions console. Select the state machine that you created previously and paste the ARN into the search bar.

The screen shows information about your specific execution. On the left, you see where your execution currently is in the workflow.

In the following screenshot, you can see that your workflow has successfully completed the alignment job and moved onto the subsequent steps, which are variant calling and generating quality information about your sample.

You can also navigate to the AWS Batch console and see that progress of all of your jobs reflected there as well.

Finally, after your workflow has completed successfully, check out the S3 path to which you wrote all of your files. If you run a ls –recursive command on the S3 results path, specified in the input to your state machine execution, you should see something similar to the following:

2017-05-02 13:46:32 6475144340 genomic-workflow/results/NA12878_run1/bam/sorted.bam
2017-05-02 13:46:34    7552576 genomic-workflow/results/NA12878_run1/bam/sorted.bam.bai
2017-05-02 13:46:32         45 genomic-workflow/results/NA12878_run1/bam/sorted.bam.md5
2017-05-02 13:53:20      68769 genomic-workflow/results/NA12878_run1/stats/bam_stats.dat
2017-05-02 14:05:12        100 genomic-workflow/results/NA12878_run1/vcf/stats/runStats.tsv
2017-05-02 14:05:12        359 genomic-workflow/results/NA12878_run1/vcf/stats/runStats.xml
2017-05-02 14:05:12  507577928 genomic-workflow/results/NA12878_run1/vcf/variants/genome.S1.vcf.gz
2017-05-02 14:05:12     723144 genomic-workflow/results/NA12878_run1/vcf/variants/genome.S1.vcf.gz.tbi
2017-05-02 14:05:12  507577928 genomic-workflow/results/NA12878_run1/vcf/variants/genome.vcf.gz
2017-05-02 14:05:12     723144 genomic-workflow/results/NA12878_run1/vcf/variants/genome.vcf.gz.tbi
2017-05-02 14:05:12   30783484 genomic-workflow/results/NA12878_run1/vcf/variants/variants.vcf.gz
2017-05-02 14:05:12    1566596 genomic-workflow/results/NA12878_run1/vcf/variants/variants.vcf.gz.tbi

Modifications to the workflow

You have now built and run your genomics workflow. While diving deep into modifications to this architecture are beyond the scope of these posts, we wanted to leave you with several suggestions of how you might modify this workflow to satisfy additional business requirements.

  • Job tracking with Amazon DynamoDB
    In many cases, such as if you are offering Genomics-as-a-Service, you might want to track the state of your jobs with DynamoDB to get fine-grained records of how your jobs are running. This way, you can easily identify the cost of individual jobs and workflows that you run.
  • Resuming from failure
    Both AWS Batch and Step Functions natively support job retries and can cover many of the standard cases where a job might be interrupted. There may be cases, however, where your workflow might fail in a way that is unpredictable. In this case, you can use custom error handling with AWS Step Functions to build out a workflow that is even more resilient. Also, you can build in fail states into your state machine to fail at any point, such as if a batch job fails after a certain number of retries.
  • Invoking Step Functions from Amazon API Gateway
    You can use API Gateway to build an API that acts as a "front door" to Step Functions. You can create a POST method that contains the input JSON to feed into the state machine you built. For more information, see the Implementing Serverless Manual Approval Steps in AWS Step Functions and Amazon API Gateway blog post.

Conclusion

While the approach we have demonstrated in this series has been focused on genomics, it is important to note that this can be generalized to nearly any high-throughput batch workload. We hope that you have found the information useful and that it can serve as a jump-start to building your own batch workloads on AWS with native AWS services.

For more information about how AWS can enable your genomics workloads, be sure to check out the AWS Genomics page.

Other posts in this four-part series:

Please leave any questions and comments below.

Building High-Throughput Genomic Batch Workflows on AWS: Batch Layer (Part 3 of 4)

Post Syndicated from Andy Katz original https://aws.amazon.com/blogs/compute/building-high-throughput-genomic-batch-workflows-on-aws-batch-layer-part-3-of-4/

Aaron Friedman is a Healthcare and Life Sciences Partner Solutions Architect at AWS

Angel Pizarro is a Scientific Computing Technical Business Development Manager at AWS

This post is the third in a series on how to build a genomics workflow on AWS. In Part 1, we introduced a general architecture, shown below, and highlighted the three common layers in a batch workflow:

  • Job
  • Batch
  • Workflow

In Part 2, you built a Docker container for each job that needed to run as part of your workflow, and stored them in Amazon ECR.

In Part 3, you tackle the batch layer and build a scalable, elastic, and easily maintainable batch engine using AWS Batch.

AWS Batch enables developers, scientists, and engineers to easily and efficiently run hundreds of thousands of batch computing jobs on AWS. It dynamically provisions the optimal quantity and type of compute resources (for example, CPU or memory optimized instances) based on the volume and specific resource requirements of the batch jobs that you submit. With AWS Batch, you do not need to install and manage your own batch computing software or server clusters, which allows you to focus on analyzing results, such as those of your genomic analysis.

Integrating applications into AWS Batch

If you are new to AWS Batch, we recommend reading Setting Up AWS Batch to ensure that you have the proper permissions and AWS environment.

After you have a working environment, you define several types of resources:

  • IAM roles that provide service permissions
  • A compute environment that launches and terminates compute resources for jobs
  • A custom Amazon Machine Image (AMI)
  • A job queue to submit the units of work and to schedule the appropriate resources within the compute environment to execute those jobs
  • Job definitions that define how to execute an application

After the resources are created, you’ll test the environment and create an AWS Lambda function to send generic jobs to the queue.

This genomics workflow covers the basic steps. For more information, see Getting Started with AWS Batch.

Creating the necessary IAM roles

AWS Batch simplifies batch processing by managing a number of underlying AWS services so that you can focus on your applications. As a result, you create IAM roles that give the service permissions to act on your behalf. In this section, deploy the AWS CloudFormation template included in the GitHub repository and extract the ARNs for later use.

To deploy the stack, go to the top level in the repo with the following command:

aws cloudformation create-stack --template-body file://batch/setup/iam.template.yaml --stack-name iam --capabilities CAPABILITY_NAMED_IAM

You can capture the output from this stack in the Outputs tab in the CloudFormation console:

Creating the compute environment

In AWS Batch, you will set up a managed compute environments. Managed compute environments automatically launch and terminate compute resources on your behalf based on the aggregate resources needed by your jobs, such as vCPU and memory, and simple boundaries that you define.

When defining your compute environment, specify the following:

  • Desired instance types in your environment
  • Min and max vCPUs in the environment
  • The Amazon Machine Image (AMI) to use
  • Percentage value for bids on the Spot Market and VPC subnets that can be used.

AWS Batch then provisions an elastic and heterogeneous pool of Amazon EC2 instances based on the aggregate resource requirements of jobs sitting in the RUNNABLE state. If a mix of CPU and memory-intensive jobs are ready to run, AWS Batch provisions the appropriate ratio and size of CPU and memory-optimized instances within your environment. For this post, you will use the simplest configuration, in which instance types are set to "optimal" allowing AWS Batch to choose from the latest C, M, and R EC2 instance families.

While you could create this compute environment in the console, we provide the following CLI commands. Replace the subnet IDs and key name with your own private subnets and key, and the image-id with the image you will build in the next section.

ACCOUNTID=<your account id>
SERVICEROLE=<from output in CloudFormation template>
IAMFLEETROLE=<from output in CloudFormation template>
JOBROLEARN=<from output in CloudFormation template>
SUBNETS=<comma delimited list of subnets>
SECGROUPS=<your security groups>
SPOTPER=50 # percentage of on demand
IMAGEID=<ami-id corresponding to the one you created>
INSTANCEROLE=<from output in CloudFormation template>
REGISTRY=${ACCOUNTID}.dkr.ecr.us-east-1.amazonaws.com
KEYNAME=<your key name>
MAXCPU=1024 # max vCPUs in compute environment
ENV=myenv

# Creates the compute environment
aws batch create-compute-environment --compute-environment-name genomicsEnv-$ENV --type MANAGED --state ENABLED --service-role ${SERVICEROLE} --compute-resources type=SPOT,minvCpus=0,maxvCpus=$MAXCPU,desiredvCpus=0,instanceTypes=optimal,imageId=$IMAGEID,subnets=$SUBNETS,securityGroupIds=$SECGROUPS,ec2KeyPair=$KEYNAME,instanceRole=$INSTANCEROLE,bidPercentage=$SPOTPER,spotIamFleetRole=$IAMFLEETROLE

Creating the custom AMI for AWS Batch

While you can use default Amazon ECS-optimized AMIs with AWS Batch, you can also provide your own image in managed compute environments. We will use this feature to provision additional scratch EBS storage on each of the instances that AWS Batch launches and also to encrypt both the Docker and scratch EBS volumes.

AWS Batch has the same requirements for your AMI as Amazon ECS. To build the custom image, modify the default Amazon ECS-Optimized Amazon Linux AMI in the following ways:

  • Attach a 1 TB scratch volume to /dev/sdb
  • Encrypt the Docker and new scratch volumes
  • Mount the scratch volume to /docker_scratch by modifying /etcfstab

The first two tasks can be addressed when you create the custom AMI in the console. Spin up a small t2.micro instance, and proceed through the standard EC2 instance launch.

After your instance has launched, record the IP address and then SSH into the instance. Copy and paste the following code:

sudo yum -y update
sudo parted /dev/xvdb mklabel gpt
sudo parted /dev/xvdb mkpart primary 0% 100%
sudo mkfs -t ext4 /dev/xvdb1
sudo mkdir /docker_scratch
sudo echo -e '/dev/xvdb1\t/docker_scratch\text4\tdefaults\t0\t0' | sudo tee -a /etc/fstab
sudo mount -a

This auto-mounts your scratch volume to /docker_scratch, which is your scratch directory for batch processing. Next, create your new AMI and record the image ID.

Creating the job queues

AWS Batch job queues are used to coordinate the submission of batch jobs. Your jobs are submitted to job queues, which can be mapped to one or more compute environments. Job queues have priority relative to each other. You can also specify the order in which they consume resources from your compute environments.

In this solution, use two job queues. The first is for high priority jobs, such as alignment or variant calling. Set this with a high priority (1000) and map back to the previously created compute environment. Next, set a second job queue for low priority jobs, such as quality statistics generation. To create these compute environments, enter the following CLI commands:

aws batch create-job-queue --job-queue-name highPriority-${ENV} --compute-environment-order order=0,computeEnvironment=genomicsEnv-${ENV}  --priority 1000 --state ENABLED
aws batch create-job-queue --job-queue-name lowPriority-${ENV} --compute-environment-order order=0,computeEnvironment=genomicsEnv-${ENV}  --priority 1 --state ENABLED

Creating the job definitions

To run the Isaac aligner container image locally, supply the Amazon S3 locations for the FASTQ input sequences, the reference genome to align to, and the output BAM file. For more information, see tools/isaac/README.md.

The Docker container itself also requires some information on a suitable mountable volume so that it can read and write files temporary files without running out of space.

Note: In the following example, the FASTQ files as well as the reference files to run are in a publicly available bucket.

FASTQ1=s3://aws-batch-genomics-resources/fastq/SRR1919605_1.fastq.gz
FASTQ2=s3://aws-batch-genomics-resources/fastq/SRR1919605_2.fastq.gz
REF=s3://aws-batch-genomics-resources/reference/isaac/
BAM=s3://mybucket/genomic-workflow/test_results/bam/

mkdir ~/scratch

docker run --rm -ti -v $(HOME)/scratch:/scratch $REPO_URI --bam_s3_folder_path $BAM \
--fastq1_s3_path $FASTQ1 \
--fastq2_s3_path $FASTQ2 \
--reference_s3_path $REF \
--working_dir /scratch 

Locally running containers can typically expand their CPU and memory resource headroom. In AWS Batch, the CPU and memory requirements are hard limits and are allocated to the container image at runtime.

Isaac is a fairly resource-intensive algorithm, as it creates an uncompressed index of the reference genome in memory to match the query DNA sequences. The large memory space is shared across multiple CPU threads, and Isaac can scale almost linearly with the number of CPU threads given to it as a parameter.

To fit these characteristics, choose an optimal instance size to maximize the number of CPU threads based on a given large memory footprint, and deploy a Docker container that uses all of the instance resources. In this case, we chose a host instance with 80+ GB of memory and 32+ vCPUs. The following code is example JSON that you can pass to the AWS CLI to create a job definition for Isaac.

aws batch register-job-definition --job-definition-name isaac-${ENV} --type container --retry-strategy attempts=3 --container-properties '
{"image": "'${REGISTRY}'/isaac",
"jobRoleArn":"'${JOBROLEARN}'",
"memory":80000,
"vcpus":32,
"mountPoints": [{"containerPath": "/scratch", "readOnly": false, "sourceVolume": "docker_scratch"}],
"volumes": [{"name": "docker_scratch", "host": {"sourcePath": "/docker_scratch"}}]
}'

You can copy and paste the following code for the other three job definitions:

aws batch register-job-definition --job-definition-name strelka-${ENV} --type container --retry-strategy attempts=3 --container-properties '
{"image": "'${REGISTRY}'/strelka",
"jobRoleArn":"'${JOBROLEARN}'",
"memory":32000,
"vcpus":32,
"mountPoints": [{"containerPath": "/scratch", "readOnly": false, "sourceVolume": "docker_scratch"}],
"volumes": [{"name": "docker_scratch", "host": {"sourcePath": "/docker_scratch"}}]
}'

aws batch register-job-definition --job-definition-name snpeff-${ENV} --type container --retry-strategy attempts=3 --container-properties '
{"image": "'${REGISTRY}'/snpeff",
"jobRoleArn":"'${JOBROLEARN}'",
"memory":10000,
"vcpus":4,
"mountPoints": [{"containerPath": "/scratch", "readOnly": false, "sourceVolume": "docker_scratch"}],
"volumes": [{"name": "docker_scratch", "host": {"sourcePath": "/docker_scratch"}}]
}'

aws batch register-job-definition --job-definition-name samtoolsStats-${ENV} --type container --retry-strategy attempts=3 --container-properties '
{"image": "'${REGISTRY}'/samtools_stats",
"jobRoleArn":"'${JOBROLEARN}'",
"memory":10000,
"vcpus":4,
"mountPoints": [{"containerPath": "/scratch", "readOnly": false, "sourceVolume": "docker_scratch"}],
"volumes": [{"name": "docker_scratch", "host": {"sourcePath": "/docker_scratch"}}]
}'

The value for "image" comes from the previous post on creating a Docker image and publishing to ECR. The value for jobRoleArn you can find from the output of the CloudFormation template that you deployed earlier. In addition to providing the number of CPU cores and memory required by Isaac, you also give it a storage volume for scratch and staging. The volume comes from the previously defined custom AMI.

Testing the environment

After you have created the Isaac job definition, you can submit the job using the AWS Batch submitJob API action. While the base mappings for Docker run are taken care of in the job definition that you just built, the specific job parameters should be specified in the container overrides section of the API call. Here’s what this would look like in the CLI, using the same parameters as in the bash commands shown earlier:

aws batch submit-job --job-name testisaac --job-queue highPriority-${ENV} --job-definition isaac-${ENV}:1 --container-overrides '{
"command": [
			"--bam_s3_folder_path", "s3://mybucket/genomic-workflow/test_batch/bam/",
            "--fastq1_s3_path", "s3://aws-batch-genomics-resources/fastq/ SRR1919605_1.fastq.gz",
            "--fastq2_s3_path", "s3://aws-batch-genomics-resources/fastq/SRR1919605_2.fastq.gz",
            "--reference_s3_path", "s3://aws-batch-genomics-resources/reference/isaac/",
            "--working_dir", "/scratch",
			"—cmd_args", " --exome ",]
}'

When you execute a submitJob call, jobId is returned. You can then track the progress of your job using the describeJobs API action:

aws batch describe-jobs –jobs <jobId returned from submitJob>

You can also track the progress of all of your jobs in the AWS Batch console dashboard.

To see exactly where a RUNNING job is at, use the link in the AWS Batch console to direct you to the appropriate location in CloudWatch logs.

Completing the batch environment setup

To finish, create a Lambda function to submit a generic AWS Batch job.

In the Lambda console, create a Python 2.7 Lambda function named batchSubmitJob. Copy and paste the following code. This is similar to the batch-submit-job-python27 Lambda blueprint. Use the LambdaBatchExecutionRole that you created earlier. For more information about creating functions, see Step 2.1: Create a Hello World Lambda Function.

from __future__ import print_function

import json
import boto3

batch_client = boto3.client('batch')

def lambda_handler(event, context):
    # Log the received event
    print("Received event: " + json.dumps(event, indent=2))
    # Get parameters for the SubmitJob call
    # http://docs.aws.amazon.com/batch/latest/APIReference/API_SubmitJob.html
    job_name = event['jobName']
    job_queue = event['jobQueue']
    job_definition = event['jobDefinition']
    
    # containerOverrides, dependsOn, and parameters are optional
    container_overrides = event['containerOverrides'] if event.get('containerOverrides') else {}
    parameters = event['parameters'] if event.get('parameters') else {}
    depends_on = event['dependsOn'] if event.get('dependsOn') else []
    
    try:
        response = batch_client.submit_job(
            dependsOn=depends_on,
            containerOverrides=container_overrides,
            jobDefinition=job_definition,
            jobName=job_name,
            jobQueue=job_queue,
            parameters=parameters
        )
        
        # Log response from AWS Batch
        print("Response: " + json.dumps(response, indent=2))
        
        # Return the jobId
        event['jobId'] = response['jobId']
        return event
    
    except Exception as e:
        print(e)
        message = 'Error getting Batch Job status'
        print(message)
        raise Exception(message)

Conclusion

In part 3 of this series, you successfully set up your data processing, or batch, environment in AWS Batch. We also provided a Python script in the corresponding GitHub repo that takes care of all of the above CLI arguments for you, as well as building out the job definitions for all of the jobs in the workflow: Isaac, Strelka, SAMtools, and snpEff. You can check the script’s README for additional documentation.

In Part 4, you’ll cover the workflow layer using AWS Step Functions and AWS Lambda.

Please leave any questions and comments below.

Build a Healthcare Data Warehouse Using Amazon EMR, Amazon Redshift, AWS Lambda, and OMOP

Post Syndicated from Ryan Hood original https://aws.amazon.com/blogs/big-data/build-a-healthcare-data-warehouse-using-amazon-emr-amazon-redshift-aws-lambda-and-omop/

In the healthcare field, data comes in all shapes and sizes. Despite efforts to standardize terminology, some concepts (e.g., blood glucose) are still often depicted in different ways. This post demonstrates how to convert an openly available dataset called MIMIC-III, which consists of de-identified medical data for about 40,000 patients, into an open source data model known as the Observational Medical Outcomes Partnership (OMOP) Common Data Model (CDM). It describes the architecture and steps for analyzing data across various disconnected sources of health datasets so you can start applying Big Data methods to health research.

Note: If you arrived at this page looking for more info on the movie Mimic 3: Sentinel, you might not enjoy this post.

OMOP overview

The OMOP CDM helps standardize healthcare data and makes it easier to analyze outcomes at a large scale. The CDM is gaining a lot of traction in the health research community, which is deeply involved in developing and adopting a common data model. Community resources are available for converting datasets, and there are software tools to help unlock your data after it’s in the OMOP format. The great advantage of converting data sources into a standard data model like OMOP is that it allows for streamlined, comprehensive analytics and helps remove the variability associated with analyzing health records from different sources.

OMOP ETL with Apache Spark

Observational Health Data Sciences and Informatics (OHDSI) provides the OMOP CDM in a variety of formats, including Apache Impala, Oracle, PostgreSQL, and SQL Server. (See the OHDSI Common Data Model repo in GitHub.) In this scenario, the data is moved to AWS to take advantage of the unbounded scale of Amazon EMR and serverless technologies, and the variety of AWS services that can help make sense of the data in a cost-effective way—including Amazon Machine Learning, Amazon QuickSight, and Amazon Redshift.

This example demonstrates an architecture that can be used to run SQL-based extract, transform, load (ETL) jobs to map any data source to the OMOP CDM. It uses MIMIC ETL code provided by Md. Shamsuzzoha Bayzid. The code was modified to run in Amazon Redshift.

Getting access to the MIMIC-III data

Before you can retrieve the MIMIC-III data, you must request access on the PhysioNet website, which is hosted on Amazon S3 as part of the Amazon Web Services (AWS) Public Dataset Program. However, you don’t need access to the MIMIC-III data to follow along with this post.

Solution architecture and loading process

The following diagram shows the architecture that is used to convert the MIMIC-III dataset to the OMOP CDM.

The data conversion process includes the following steps:

  1. The entire infrastructure is spun up using an AWS CloudFormation template. This includes the Amazon EMR cluster, Amazon SNS topics/subscriptions, an AWS Lambda function and trigger, and AWS Identity and Access Management (IAM) roles.
  2. The MIMIC-III data is read in via an Apache Spark program that is running on Amazon EMR. The files are registered as tables in Spark so that they can be queried by Spark SQL.
  3. The transformation queries are located in a separate Amazon S3 location, which is read in by Spark and executed on the newly registered tables to convert the data into OMOP form.
  4. The data is then written to a staging S3 location, where it is ready to be copied into Amazon Redshift.
  5. As each file is loaded in OMOP form into S3, the Spark program sends a message to an SNS topic that signifies that the load completed successfully.
  6. After that message is pushed, it triggers a Lambda function that consumes the message and executes a COPY command from S3 into Amazon Redshift for the appropriate table.

This architecture provides a scalable way to use various healthcare sources and convert them to OMOP format, where the only changes needed are in the SQL transformation files. The transformation logic is stored in an S3 bucket and is completely de-coupled from the Apache Spark program that runs on EMR and converts the data into OMOP form. This makes the transformation code portable and allows the Spark jar to be reused if other data sources are added—for example, electronic health records (EHR), billing systems, and other research datasets.

Note: For larger files, you might experience the five-minute timeout limitation in Lambda. In that scenario you can use AWS Step Functions to split the file and load it one piece at a time.

Scaling the solution

The transformation code runs in a Spark container that can scale out based on how you define your EMR cluster. There are no single points of failure. As your data grows, your infrastructure can grow without requiring any changes to the underlying architecture.

If you add more data sources, such as EHRs and other research data, the high-level view of the ETL would look like the following:

In this case, the loads of the different systems are completely independent. If the EHR load is four times the size that you expected and uses all the resources, it has no impact on the Research Data or HR System loads because they are in separate containers.

You can scale your EMR cluster based on the size of the data that you anticipate. For example, you can have a 50-node cluster in your container for loading EHR data and a 2-node cluster for loading the HR System. This design helps you scale the resources based on what you consume, as opposed to expensive infrastructure sitting idle.

The only code that is unique to each execution is any diffs between the CloudFormation templates (e.g., cluster size and SQL file locations) and the transformation SQL that resides in S3 buckets. The Spark jar that is executed as an EMR step is reused across all three executions.

Upgrading versions

In this architecture, upgrading the versions of Amazon EMR, Apache Hadoop, or Spark requires a one-time change to one line of code in the CloudFormation template:

"EMRC2SparkBatch": {
      "Type": "AWS::EMR::Cluster",
      "Properties": {
        "Applications": [
          {
            "Name": "Hadoop"
          },
          {
            "Name": "Spark"
          }
        ],
        "Instances": {
          "MasterInstanceGroup": {
            "InstanceCount": 1,
            "InstanceType": "m3.xlarge",
            "Market": "ON_DEMAND",
            "Name": "Master"
          },
          "CoreInstanceGroup": {
            "InstanceCount": 1,
            "InstanceType": "m3.xlarge",
            "Market": "ON_DEMAND",
            "Name": "Core"
          },
          "TerminationProtected": false
        },
        "Name": "EMRC2SparkBatch",
        "JobFlowRole": { "Ref": "EMREC2InstanceProfile" },
          "ServiceRole": {
                    "Ref": "EMRRole"
                  },
        "ReleaseLabel": "emr-5.0.0",
        "VisibleToAllUsers": true      
}
    }

Note that this example uses a slightly lower version of EMR so that it can use Spark 2.0.0 instead of Spark 2.1.0, which does not support nulls in CSV files.

You can also select the version in the Release list in the General Configuration section of the EMR console:

The data sources all have different CloudFormation templates, so you can upgrade one data source at a time or upgrade them all together. As long as the reusable Spark jar is compatible with the new version, none of the transformation code has to change.

Executing queries on the data

After all the data is loaded, it’s easy to tear down the CloudFormation stack so you don’t pay for resources that aren’t being used:

CloudFormationManager cf = new CloudFormationManager(); 
cf.terminateStack(stack);    

This includes the EMR cluster, Lambda function, SNS topics and subscriptions, and temporary IAM roles that were created to push the data to Amazon Redshift. The S3 buckets that contain the raw MIMIC-III data and the data in OMOP form remain because they existed outside the CloudFormation stack.

You can now connect to the Amazon Redshift cluster and start executing queries on the ten OMOP tables that were created, as shown in the following example:

select *
from drug_exposure
limit 100;

OMOP analytics tools

For information about open source analytics tools that are built on top of the OMOP model, visit the OHDSI Software page.

The following are examples of data visualizations provided by Achilles, an open source visualization tool for OMOP.

Conclusion

This post demonstrated how to convert MIMIC-III data into OMOP form using data tools that are built for scale and flexibility. It compared the architecture against a traditional data warehouse and showed how this design scales by mixing a scale-out technology with EMR and a serverless technology with Lambda. It also showed how you can lower your costs by using CloudFormation to create your data pipeline infrastructure. And by tearing down the stack after the data is loaded, you don’t pay for idle servers.

You can find all the code in the AWS Labs GitHub repo with detailed, step-by-step instructions on how to load the data from MIMIC-III to OMOP using this design.

If you have any questions or suggestions, please add them below.


About the Author

Ryan Hood is a Data Engineer for AWS. He works on big data projects leveraging the newest AWS offerings. In his spare time, he enjoys watching the Cubs win the World Series and attempting to Sous-vide anything he can find in his refrigerator.

 

 


Related

Create a Healthcare Data Hub with AWS and Mirth Connect

 

 

 

 

 

 

 

AWS Online Tech Talks – May 2017

Post Syndicated from Tara Walker original https://aws.amazon.com/blogs/aws/aws-online-tech-talks-may-2017/

Spring has officially sprung. As you enjoy the blossoming of May flowers, it may be worthy to also note some of the great tech talks blossoming online during the month of May. This month’s AWS Online Tech Talks features sessions on topics like AI, DevOps, Data, and Serverless just to name a few.

May 2017 – Schedule

Below is the upcoming schedule for the live, online technical sessions scheduled for the month of May. Make sure to register ahead of time so you won’t miss out on these free talks conducted by AWS subject matter experts. All schedule times for the online tech talks are shown in the Pacific Time (PDT) time zone.

Webinars featured this month are:

Monday, May 15

Artificial Intelligence

9:00 AM – 10:00 AM: Integrate Your Amazon Lex Chatbot with Any Messaging Service

 

Tuesday, May 16

Compute

10:30 AM – 11:30 AM: Deep Dive on Amazon EC2 F1 Instance

IoT

12:00 Noon – 1:00 PM: How to Connect Your Own Creations with AWS IoT

Wednesday, May 17

Management Tools

9:00 AM – 10:00 AM: OpsWorks for Chef Automate – Automation Made Easy!

Serverless

10:30 AM – 11:30 AM: Serverless Orchestration with AWS Step Functions

Enterprise & Hybrid

12:00 Noon – 1:00 PM: Moving to the AWS Cloud: An Overview of the AWS Cloud Adoption Framework

 

Thursday, May 18

Compute

9:00 AM – 10:00 AM: Scaling Up Tenfold with Amazon EC2 Spot Instances

Big Data

10:30 AM – 11:30 AM: Building Analytics Pipelines for Games on AWS

12:00 Noon – 1:00 PM: Serverless Big Data Analytics using Amazon Athena and Amazon QuickSight

 

Monday, May 22

Artificial Intelligence

9:00 AM – 10:00 AM: What’s New with Amazon Rekognition

Serverless

10:30 AM – 11:30 AM: Building Serverless Web Applications

 

Tuesday, May 23

Hands-On Lab

8:30 – 10:00 AM: Hands On Lab: Windows Workloads on AWS

Big Data

10:30 AM – 11:30 AM: Streaming ETL for Data Lakes using Amazon Kinesis Firehose

DevOps

12:00 Noon – 1:00 PM: Deep Dive: Continuous Delivery for AI Applications with ECS

 

Wednesday, May 24

Storage

9:00 – 10:00 AM: Moving Data into the Cloud with AWS Transfer Services

Containers

12:00 Noon – 1:00 PM: Building a CICD Pipeline for Container Deployment to Amazon ECS

 

Thursday, May 25

Mobile

9:00 – 10:00 AM: Test Your Android App with Espresso and AWS Device Farm

Security & Identity

10:30 AM – 11:30 AM: Advanced Techniques for Federation of the AWS Management Console and Command Line Interface (CLI)

 

Tuesday, May 30

Databases

9:00 – 10:00 AM: DynamoDB: Architectural Patterns and Best Practices for Infinitely Scalable Applications

Compute

10:30 AM – 11:30 AM: Deep Dive on Amazon EC2 Elastic GPUs

Security & Identity

12:00 Noon – 1:00 PM: Securing Your AWS Infrastructure with Edge Services

 

Wednesday, May 31

Hands-On Lab

8:30 – 10:00 AM: Hands On Lab: Introduction to Microsoft SQL Server in AWS

Enterprise & Hybrid

10:30 AM – 11:30 AM: Best Practices in Planning a Large-Scale Migration to AWS

Databases

12:00 Noon – 1:00 PM: Convert and Migrate Your NoSQL Database or Data Warehouse to AWS

 

The AWS Online Tech Talks series covers a broad range of topics at varying technical levels. These sessions feature live demonstrations & customer examples led by AWS engineers and Solution Architects. Check out the AWS YouTube channel for more on-demand webinars on AWS technologies.

Tara

Automating AWS Lambda Function Error Handling with AWS Step Functions

Post Syndicated from Andy Katz original https://aws.amazon.com/blogs/compute/automating-aws-lambda-function-error-handling-with-aws-step-functions/

Aaron Rehaag
Aaron Rehaag, Senior Software Engineer, Amazon Web Services

AWS Step Functions makes it easy to coordinate the components of distributed applications and microservices using visual workflows. You can scale and modify your applications quickly by building applications from individual components, each of which performs a discrete function.

You can use Step Functions to create state machines, which orchestrate multiple AWS Lambda functions to build multi-step serverless applications. In certain cases, a Lambda function returns an error. Regardless of whether the error is a function exception created by the developer (e.g., file not found), or unpredicted (e.g., out of memory), Step Functions allows you to respond with conditional logic based on the type of error message in the form of function error handling.

Function error handling

The function error handling feature of Task states allows you to raise an exception directly from a Lambda function and handle it (using Retry or Catch) directly within a Step Functions state machine.

Consider the following state machine designed to sign up new customers for an account:

stepFunctionsErrorHandle_1.png

CreateAccount is a Task state, which writes a customer’s account details to a database using a Lambda function.

If the task succeeds, an account is created, and the state machine progresses from the CreateAccount Task state to the SendWelcomeEmail Task state to send an email to welcome the customer.

However, if a customer tries to register an account with a username already in use, the state machine suggests a different name to the user and retries the account creation process. The Lambda function raises an error, triggering the Catch clause. This causes the state machine to transition to the CreateAccount task state, suggesting a new name before transitioning back to the SuggestAccountState.

You can implement this scenario using any of the programming languages that Step Functions and Lambda support, which currently include Node.js, Java, C#, and Python. The following sections show how to implement a Catch clause in each language.

Node.js

Function errors in Node.js must extend from the Error prototype:

exports.handler = function(event, context, callback) {
    function AccountAlreadyExistsError(message) {
        this.name = "AccountAlreadyExistsError";
        this.message = message;
    }
    
    AccountAlreadyExistsError.prototype = new Error();
    const error = new AccountAlreadyExistsError("Account is in use!");
    callback(error);
};

You can configure Step Functions to catch the error using a Catch rule:

{
   "StartAt": "CreateAccount",
   "States": {
      "CreateAccount": {
         "Type": "Task",
         "Resource": "arn:aws:lambda:us-east-1:123456789012:function:CreateAccount",
         "Next": "SendWelcomeEmail",
         "Catch": [
            {
               "ErrorEquals": ["AccountAlreadyExistsError"],
               "Next": "SuggestAccountName"
            }
         ]
      },

      …

   }
}

At runtime, Step Functions catches the error, transitioning to the SuggestAccountName state as specified in the Next transition.

Note: The name property of the Error object must match the ErrorEquals value.

Java

You can apply the same scenario to a Lambda Java function by extending the Exception class:

package com.example;

public static class AccountAlreadyExistsException extends Exception {
    public AccountAlreadyExistsException(String message) {
        super(message);
    }
}
package com.example;

import com.amazonaws.services.lambda.runtime.Context; 

public class Handler {
    public static void CreateAccount(String name, Context context) throws AccountAlreadyExistsException {
        throw new AccountAlreadyExistsException ("Account is in use!");
    }
}

Lambda automatically sets the error name to the fully-qualified class name of the exception at runtime:

{
   "StartAt": "CreateAccount",
   "States": {
      "CreateAccount": {
         "Type": "Task",
         "Resource": "arn:aws:lambda:us-east-1:123456789012:function:CreateAccount",
         "Next": "SendWelcomeEmail",
         "Catch": [
            {
               "ErrorEquals": ["com.example.AccountAlreadyExistsException"],
               "Next": "SuggestAccountName"
            }
         ]
      },

      …

   }
}

C-Sharp

In C#, specify function errors by extending the Exception class:

namespace Example {
   public class AccountAlreadyExistsException : Exception {
      public AccountAlreadyExistsException(String message) :
         base(message) {
      }
   }
}
namespace Example {
   public class Handler {
     public static void CreateAccount() {
       throw new AccountAlreadyExistsException("Account is in use!");
     }
   }
} 

Lambda automatically sets the error name to the simple class name of the exception at runtime:

{
   "StartAt": "CreateAccount",
   "States": {
      "CreateAccount": {
         "Type": "Task",
         "Resource": "arn:aws:lambda:us-east-1:123456789012:function:CreateAccount",
         "Next": "SendWelcomeEmail",
         "Catch": [
            {
               "ErrorEquals": ["AccountAlreadyExistsException"],
               "Next": "SuggestAccountName"
            }
         ]
      },

      …

   }
}

Python

In Python, specify function errors by extending the Exception class:

def create_account(event, context):
    class AccountAlreadyExistsException(Exception):
        pass
        
    raise AccountAlreadyExistsException('Account is in use!')

Lambda automatically sets the error name to the simple class name of the exception at runtime:

{
   "StartAt": "CreateAccount",
   "States": {
      "CreateAccount": {
         "Type": "Task",
         "Resource": "arn:aws:lambda:us-east-1:123456789012:function:CreateAccount",
         "Next": "SendWelcomeEmail",
         "Catch": [
            {
               "ErrorEquals": ["AccountAlreadyExistsException"],
               "Next": "SuggestAccountName"
            }
         ]
      },

      …

   }
}

Getting started with error handling

The function error handling feature of Step Functions makes it easier to create serverless applications. In addition to the Catch clause shown in this post, you can apply the same pattern to Retry of failed Lambda functions.

While you can create Catch and Retry patterns using a Choice state, using Catch and Retry in your Task states allows you to separate exceptions from branching logic associated with the common happy paths through your state machines. Function error handling integrates with all supported Lambda programming models, so you are free to design your application in the programming languages of your choice, mixing and matching as you go.

To create your own serverless applications using Step Functions, see the AWS Step Functions product page.

AWS Week in Review – March 6, 2017

Post Syndicated from Jeff Barr original https://aws.amazon.com/blogs/aws/aws-week-in-review-march-6-2017/

This edition includes all of our announcements, content from all of our blogs, and as much community-generated AWS content as I had time for!

Monday

March 6

Tuesday

March 7

Wednesday

March 8

Thursday

March 9

Friday

March 10

Saturday

March 11

Sunday

March 12

Jeff;

 

Implementing Serverless Manual Approval Steps in AWS Step Functions and Amazon API Gateway

Post Syndicated from Bryan Liston original https://aws.amazon.com/blogs/compute/implementing-serverless-manual-approval-steps-in-aws-step-functions-and-amazon-api-gateway/


Ali Baghani, Software Development Engineer

A common use case for AWS Step Functions is a task that requires human intervention (for example, an approval process). Step Functions makes it easy to coordinate the components of distributed applications as a series of steps in a visual workflow called a state machine. You can quickly build and run state machines to execute the steps of your application in a reliable and scalable fashion.

In this post, I describe a serverless design pattern for implementing manual approval steps. You can use a Step Functions activity task to generate a unique token that can be returned later indicating either approval or rejection by the person making the decision.

Key steps to implementation

When the execution of a Step Functions state machine reaches an activity task state, Step Functions schedules the activity and waits for an activity worker. An activity worker is an application that polls for activity tasks by calling GetActivityTask. When the worker successfully calls the API action, the activity is vended to that worker as a JSON blob that includes a token for callback.

At this point, the activity task state and the branch of the execution that contains the state is paused. Unless a timeout is specified in the state machine definition, which can be up to one year, the activity task state waits until the activity worker calls either SendTaskSuccess or SendTaskFailure using the vended token. This pause is the first key to implementing a manual approval step.

The second key is the ability in a serverless environment to separate the code that fetches the work and acquires the token from the code that responds with the completion status and sends the token back, as long as the token can be shared, i.e., the activity worker in this example is a serverless application supervised by a single activity task state.

In this walkthrough, you use a short-lived AWS Lambda function invoked on a schedule to implement the activity worker, which acquires the token associated with the approval step, and prepares and sends an email to the approver using Amazon SES.

It is very convenient if the application that returns the token can directly call the SendTaskSuccess and SendTaskFailure API actions on Step Functions. This can be achieved more easily by exposing these two actions through Amazon API Gateway so that an email client or web browser can return the token to Step Functions. By combining a Lambda function that acquires the token with the application that returns the token through API Gateway, you can implement a serverless manual approval step, as shown below.

In this pattern, when the execution reaches a state that requires manual approval, the Lambda function prepares and sends an email to the user with two embedded hyperlinks for approval and rejection.

If the authorized user clicks on the approval hyperlink, the state succeeds. If the authorized user clicks on the rejection link, the state fails. You can also choose to set a timeout for approval and, upon timeout, take action, such as resending the email request using retry/catch conditions in the activity task state.

Employee promotion process

As an example pattern use case, you can design a simple employee promotion process which involves a single task: getting a manager’s approval through email. When an employee is nominated for promotion, a new execution starts. The name of the employee and the email address of the employee’s manager are provided to the execution.

You’ll use the design pattern to implement the manual approval step, and SES to send the email to the manager. After acquiring the task token, the Lambda function generates and sends an email to the manager with embedded hyperlinks to URIs hosted by API Gateway.

In this example, I have administrative access to my account, so that I can create IAM roles. Moreover, I have already registered my email address with SES, so that I can send emails with the address as the sender/recipient. For detailed instructions, see Send an Email with Amazon SES.

Here is a list of what you do:

  1. Create an activity
  2. Create a state machine
  3. Create and deploy an API
  4. Create an activity worker Lambda function
  5. Test that the process works

Create an activity

In the Step Functions console, choose Tasks and create an activity called ManualStep.

stepfunctionsfirst_1.png

Remember to keep the ARN of this activity at hand.

stepfunctionsfirst_2.png

Create a state machine

Next, create the state machine that models the promotion process on the Step Functions console. Use StatesExecutionRole-us-east-1, the default role created by the console. Name the state machine PromotionApproval, and use the following code. Remember to replace the value for Resource with your activity ARN.

{
  "Comment": "Employee promotion process!",
  "StartAt": "ManualApproval",
  "States": {
    "ManualApproval": {
      "Type": "Task",
      "Resource": "arn:aws:states:us-east-1:ACCOUNT_ID:activity:ManualStep",
      "TimeoutSeconds": 3600,
      "End": true
    }
  }
}

Create and deploy an API

Next, create and deploy public URIs for calling the SendTaskSuccess or SendTaskFailure API action using API Gateway.

First, navigate to the IAM console and create the role that API Gateway can use to call Step Functions. Name the role APIGatewayToStepFunctions, choose Amazon API Gateway as the role type, and create the role.

After the role has been created, attach the managed policy AWSStepFunctionsFullAccess to it.

stepfunctionsfirst_3.png

In the API Gateway console, create a new API called StepFunctionsAPI. Create two new resources under the root (/) called succeed and fail, and for each resource, create a GET method.

stepfunctionsfirst_4.png

You now need to configure each method. Start by the /fail GET method and configure it with the following values:

  • For Integration type, choose AWS Service.
  • For AWS Service, choose Step Functions.
  • For HTTP method, choose POST.
  • For Region, choose your region of interest instead of us-east-1. (For a list of regions where Step Functions is available, see AWS Region Table.)
  • For Action Type, enter SendTaskFailure.
  • For Execution, enter the APIGatewayToStepFunctions role ARN.

stepfunctionsfirst_5.png

To be able to pass the taskToken through the URI, navigate to the Method Request section, and add a URL Query String parameter called taskToken.

stepfunctionsfirst_6.png

Then, navigate to the Integration Request section and add a Body Mapping Template of type application/json to inject the query string parameter into the body of the request. Accept the change suggested by the security warning. This sets the body pass-through behavior to When there are no templates defined (Recommended). The following code does the mapping:

{
   "cause": "Reject link was clicked.",
   "error": "Rejected",
   "taskToken": "$input.params('taskToken')"
}

When you are finished, choose Save.

Next, configure the /succeed GET method. The configuration is very similar to the /fail GET method. The only difference is for Action: choose SendTaskSuccess, and set the mapping as follows:

{
   "output": "\"Approve link was clicked.\"",
   "taskToken": "$input.params('taskToken')"
}

The last step on the API Gateway console after configuring your API actions is to deploy them to a new stage called respond. You can test our API by choosing the Invoke URL links under either of the GET methods. Because no token is provided in the URI, a ValidationException message should be displayed.

stepfunctionsfirst_7.png

Create an activity worker Lambda function

In the Lambda console, create a Lambda function with a CloudWatch Events Schedule trigger using a blank function blueprint for the Node.js 4.3 runtime. The rate entered for Schedule expression is the poll rate for the activity. This should be above the rate at which the activities are scheduled by a safety margin.

The safety margin accounts for the possibility of lost tokens, retried activities, and polls that happen while no activities are scheduled. For example, if you expect 3 promotions to happen, in a certain week, you can schedule the Lambda function to run 4 times a day during that week. Alternatively, a single Lambda function can poll for multiple activities, either in parallel or in series. For this example, use a rate of one time per minute but do not enable the trigger yet.

stepfunctionsfirst_8.png

Next, create the Lambda function ManualStepActivityWorker using the following Node.js 4.3 code. The function receives the taskToken, employee name, and manager’s email from StepFunctions. It embeds the information into an email, and sends out the email to the manager.


'use strict';
console.log('Loading function');
const aws = require('aws-sdk');
const stepfunctions = new aws.StepFunctions();
const ses = new aws.SES();
exports.handler = (event, context, callback) => {
    
    var taskParams = {
        activityArn: 'arn:aws:states:us-east-1:ACCOUNT_ID:activity:ManualStep'
    };
    
    stepfunctions.getActivityTask(taskParams, function(err, data) {
        if (err) {
            console.log(err, err.stack);
            context.fail('An error occured while calling getActivityTask.');
        } else {
            if (data === null) {
                // No activities scheduled
                context.succeed('No activities received after 60 seconds.');
            } else {
                var input = JSON.parse(data.input);
                var emailParams = {
                    Destination: {
                        ToAddresses: [
                            input.managerEmailAddress
                            ]
                    },
                    Message: {
                        Subject: {
                            Data: 'Your Approval Needed for Promotion!',
                            Charset: 'UTF-8'
                        },
                        Body: {
                            Html: {
                                Data: 'Hi!<br />' +
                                    input.employeeName + ' has been nominated for promotion!<br />' +
                                    'Can you please approve:<br />' +
                                    'https://API_DEPLOYMENT_ID.execute-api.us-east-1.amazonaws.com/respond/succeed?taskToken=' + encodeURIComponent(data.taskToken) + '<br />' +
                                    'Or reject:<br />' +
                                    'https://API_DEPLOYMENT_ID.execute-api.us-east-1.amazonaws.com/respond/fail?taskToken=' + encodeURIComponent(data.taskToken),
                                Charset: 'UTF-8'
                            }
                        }
                    },
                    Source: input.managerEmailAddress,
                    ReplyToAddresses: [
                            input.managerEmailAddress
                        ]
                };
                    
                ses.sendEmail(emailParams, function (err, data) {
                    if (err) {
                        console.log(err, err.stack);
                        context.fail('Internal Error: The email could not be sent.');
                    } else {
                        console.log(data);
                        context.succeed('The email was successfully sent.');
                    }
                });
            }
        }
    });
};

In the Lambda function handler and role section, for Role, choose Create a new role, LambdaManualStepActivityWorkerRole.

stepfunctionsfirst_9.png

Add two policies to the role: one to allow the Lambda function to call the GetActivityTask API action by calling Step Functions, and one to send an email by calling SES. The result should look as follows:

{
  "Version": "2012-10-17",
  "Statement": [
    {
      "Effect": "Allow",
      "Action": [
        "logs:CreateLogGroup",
        "logs:CreateLogStream",
        "logs:PutLogEvents"
      ],
      "Resource": "arn:aws:logs:*:*:*"
    },
    {
      "Effect": "Allow",
      "Action": "states:GetActivityTask",
      "Resource": "arn:aws:states:*:*:activity:ManualStep"
    },
    {
      "Effect": "Allow",
      "Action": "ses:SendEmail",
      "Resource": "*"
    }
  ]
}

In addition, as the GetActivityTask API action performs long-polling with a timeout of 60 seconds, increase the timeout of the Lambda function to 1 minute 15 seconds. This allows the function to wait for an activity to become available, and gives it extra time to call SES to send the email. For all other settings, use the Lambda console defaults.

stepfunctionsfirst_10.png

After this, you can create your activity worker Lambda function.

Test the process

You are now ready to test the employee promotion process.

In the Lambda console, enable the ManualStepPollSchedule trigger on the ManualStepActivityWorker Lambda function.

In the Step Functions console, start a new execution of the state machine with the following input:

{ "managerEmailAddress": "[email protected]", "employeeName" : "Jim" } 

Within a minute, you should receive an email with links to approve or reject Jim’s promotion. Choosing one of those links should succeed or fail the execution.

stepfunctionsfirst_11.png

Summary

In this post, you created a state machine containing an activity task with Step Functions, an API with API Gateway, and a Lambda function to dispatch the approval/failure process. Your Step Functions activity task generated a unique token that was returned later indicating either approval or rejection by the person making the decision. Your Lambda function acquired the task token by polling the activity task, and then generated and sent an email to the manager for approval or rejection with embedded hyperlinks to URIs hosted by API Gateway.

If you have questions or suggestions, please comment below.

Continuous Deployment for Serverless Applications

Post Syndicated from Bryan Liston original https://aws.amazon.com/blogs/compute/continuous-deployment-for-serverless-applications/

With a continuous deployment infrastructure, developers can quickly and safely release new features and bug fixes for their applications without manually triggering any deployment scripts. Amazon Web Services offers a number of products that make the creation of deployment pipelines easier:

A typical serverless application consists of one or more functions triggered by events such as object uploads to Amazon S3, Amazon SNS notifications, or API actions. Those functions can stand alone or leverage other resources such as Amazon DynamoDB tables or S3 buckets. The most basic serverless application is simply a function.

This post shows you how to leverage AWS services to create a continuous deployment pipeline for your serverless applications. You use the Serverless Application Model (SAM) to define the application and its resources, CodeCommit as your source repository, CodeBuild to package your source code and SAM templates, AWS CloudFormation to deploy your application, and CodePipeline to bring it all together and orchestrate your application deployment.

Creating a pipeline

Pipelines pick up source code changes from a repository, build and package the application, and then push the new update through a series of stages, running integration tests to ensure that all features are intact and backward-compatible on each stage.

Each stage uses its own resources; for example, if you have a "dev" stage that points to a "dev" function, they are completely separate from the "prod" stage that points to a "prod" function. If your application uses other AWS services, such as S3 or DynamoDB, you should also have different resources for each stage. You can use environment variables in your AWS Lambda function to parameterize the resource names in the Lambda code.

To make this easier for you, we have created a CloudFormation template that deploys the required resources. If your application conforms to the same specifications as our sample, this pipeline will work for you:

  • The source repository contains an application SAM file and a test SAM file.
  • The SAM file called app-sam.yaml defines all of the resources and functions used by the application. In the sample, this is a single function that uses the Express framework and the aws-serverless-express library.
  • The application SAM template exports the API endpoint generated in a CloudFormation output variable called ApiUrl.
  • The SAM file called test-sam.yaml defines a single function in charge of running the integration tests on each stage of the deployment.
  • The test SAM file exports the name of the Lambda function that it creates to a CloudFormation output variable called TestFunction.

You can find the link to start the pipeline deployment at the end of this section. The template asks for a name for the service being deployed (the sample is called TimeService) and creates a CodeCommit repository to hold the application’s source code, a CodeBuild project to package the SAM templates and prepare them for deployment, an S3 bucket to store build artifacts along the way, and a multi-stage CodePipeline pipeline for deployments.

The pipeline picks up your code when it’s committed to the source repository, runs the build process, and then proceeds to start the deployment to each stage. Before moving on to the next stage, the pipeline also executes integration tests: if the tests fail, the pipeline stops.

This pipeline consists of six stages:

  1. Source – the source step picks up new commits from the CodeCommit repository. CodePipeline also supports S3 and GitHub as sources for this step.
  2. Build – Using CodeBuild, you pull down your application’s dependencies and use the AWS CLI to package your app and test SAM templates for deployment. The buildspec.yml file in the root of the sample application defines the commands that CodeBuild executes at each step.
  3. DeployTests – In the first step, you deploy the updated integration tests using the test-sam.yaml file from your application. You deploy the updated tests first so that they are ready to run on all the following stages of the pipeline.
  4. Beta – This is the first step for your app’s deployment. Using the SAM template packaged in the Build step, you deploy the Lambda function and API Gateway endpoint to the beta stage. At the end of the deployment, this stage run your test function against the beta API.
  5. Gamma – Push the updated function and API to the gamma stage, then run the integration tests again.
  6. Prod – Rinse, repeat. Before proceeding with the prod deployment, your sample pipeline has a manual approval step.

Running the template

  1. Choose Launch Stack below to create the pipeline in your AWS account. This button takes you to the Create stack page of the CloudFormation console with the S3 link to the pre-populated template.
  2. Choose Next and customize your StackName and ServiceName.
  3. Skip the Options screen, choose Next, acknowledge the fact that the template can create IAM roles in your account, and choose Create.


Running integration tests

Integration tests decide whether your pipeline can move on and deploy the app code to the next stage. To keep the pipeline completely serverless, we decided to use a Lambda function to run the integration tests.

To run the test function, the pipeline template also includes a Lambda function called <YourServiceName>_start_tests. The start_tests function reads the output of the test deployment CloudFormation stack as well as the current stage’s stack, extracts the output values from the stacks (the API endpoint and the test function name), and triggers an asynchronous execution of the test function. The test function is then in charge of updating the CodePipeline job status with the outcome of the tests. The test function in the sample application generates a random success or failure output.

In the future, for more complex integration tests, you could use AWS Step Functions to execute multiple tests at the same time.

The sample application

The sample application is a very simple API; it exposes time and time/{timeZone} endpoints that return the current time. The code for the application is written in JavaScript and uses the moment-timezone library to generate and format the timestamps. Download the source code for the sample application.

The source code includes the application itself under the app folder, and the integration tests for the application under the test folder. In the root directory for the sample, you will find two SAM templates, one for the application and one for the test function. The buildspec.yml file contains the instructions for the CodeBuild container. At the moment, the buildspecs use npm to download the app’s dependencies and then the CloudFormation package command of the AWS CLI to prepare the SAM deployment package. For a sophisticated application, you would run your unit tests in the build step.

After you have downloaded the sample code, you can push it to the CodeCommit repository created by the pipeline template. The app-sam.yaml and test-sam.yaml files should be in the root of the repository. Using the CodePipeline console, you can follow the progress of the application deployment. The first time the source code is imported, the deployment can take a few minutes to start. Keep in mind that for the purpose of this demo, the integration tests function generates random failures.

After the application is deployed to a stage, you can find the API endpoint URL in the CloudFormation console by selecting the correct stack in the list and opening the Outputs tab in the bottom frame.

Conclusion

Continuous deployment and integration are a must for modern application development. It allows teams to iterate on their app at a faster clip and deliver new features and fixes in customers’ hands quickly. With this pipeline template, you can bring this automation to your serverless applications without writing any additional code or managing any infrastructure.

You can re-use the same pipeline template for multiple services. The only requirement is that they conform to the same structure as the sample app with the app-sam.yaml and test-sam.yaml in the same repository.

Serverless at re:Invent 2016 – Wrap-up

Post Syndicated from Bryan Liston original https://aws.amazon.com/blogs/compute/serverless-at-reinvent-2016-wrap-up/

The re:Invent 2016 conference was an exciting week to be working on serverless at AWS. We announced new features like support for C# and dead letter queues, and launched new application constructs with Lambda such as [email protected], AWS Greengrass, Amazon Lex, and AWS Step Functions. In addition we also added support for surfacing services built using API Gateway in the AWS marketplace, expanded the capabilities for custom authorizers, and launched a reference developer portal for managing APIs. Catch up on all the great re:Invent launches here.

In addition to the serverless mini-con with deep dive talks and best practices, we also had deep customer talks by folks from Thomson Reuters, Vevo, Expedia, and FINRA. If you weren’t able to attend the mini-con or missed a specific session, here is a quick link to the entire Serverless Mini Conference Playlist. Other interesting sessions from other tracks are listed below.

Individual Sessions from the Mini Conference

Other Interesting Sessions

If there are other sessions or talks you think I should capture in this list, let me know!

New – AWS Step Functions – Build Distributed Applications Using Visual Workflows

Post Syndicated from Jeff Barr original https://aws.amazon.com/blogs/aws/new-aws-step-functions-build-distributed-applications-using-visual-workflows/

We want to make it even easier for you to build complex, distributed applications by connecting multiple web and microservices. Whether you are implementing a complex business process or setting up a processing pipeline for photo uploads, we want you to focus on the code instead of on the coordination. We want you to be able to build reliable applications that are robust, scalable, and cost-effective, while you use the tools and libraries that you are already familiar with.

How does that sound?

Introducing AWS Step Functions
Today we are launching AWS Step Functions to allow you to do exactly what I described above. You can coordinate the components of your application as series of steps in a visual workflow. You create state machines in the Step Functions Console to specify and execute the steps of your application at scale.

Each state machine defines a set of states and the transitions between them. States can be activated sequentially or in parallel; Step Functions will make sure that all parallel states run to completion before moving forward. States perform work, make decisions, and control progress through the state machine.

Here’s a state machine that includes a little bit of everything:

Multiple copies of each state machine can be running independently at the same time; each copy is called an execution. Step Functions will let you run thousands of execution concurrently so you can scale to any desired level.

There are two different ways to specify what you want to happen when a state is run. First, you can supply a Lambda function that will be synchronously invoked when the state runs. Second, you can supply the name of an Activity. This is a reference to a long-running worker function that polls (via the API) for work to be done. Either way, the code is supplied with a JSON statement as input, and is expected to return another JSON statement as output.

As part of your state machine, you can specify error handling behavior and retry logic. This allows you to build robust multi-step apps that will run smoothly even if transient issues in one part of your code cause a momentary failure.

Quick Tour
Let’s set up a state machine through the AWS Management Console. Keep in mind that production applications will most likely use the AWS Step Functions API (described below) to create and run state machines.

I start by creating and saving a simple Lambda function:

While I am there I also capture the function’s ARN:

Then I go over to the AWS Step Functions Console and click on Create a State Machine. I enter a name (MyStateMachine), and I can click on one of the blueprints to get a running start:

I start with Hello World and use elements of Parallel to create this JSON model of my state machine:

{
  "Comment": "A simple example of the Steps language using an AWS Lambda Function",
  "StartAt": "Hello",

  "States": {
    "Hello": {
      "Type": "Task",
      "Resource": "arn:aws:lambda:eu-west-1:99999999999:function:HelloWord_Step",
      "Next": "Parallel"
    },

    "Parallel": {
      "Type": "Parallel",
      "Next": "Goodbye",
      "Branches": [
        {
          "StartAt": "p1",
          "States": {
            "p1": {
                  "Type": "Task",
                  "Resource": "arn:aws:lambda:eu-west-1:9999999999:function:HelloWord_Step",
              "End": true
            }
          }
        },

        {
          "StartAt": "p2",
          "States": {
            "p2": {
                  "Type": "Task",
                  "Resource": "arn:aws:lambda:eu-west-1:99999999999:function:HelloWord_Step",
              "End": true
            }
          }
        }
      ]
    },

    "Goodbye": {
      "Type": "Task",
      "Resource": "arn:aws:lambda:eu-west-1:99999999999:function:HelloWord_Step",
      "End": true
    }
  }
}

I click on Preview to see it graphically:

Then I select the IAM role that Step Functions thoughtfully created for me:

And I am all set! Now I can execute my state machine from the console; I can start it off with a block of JSON that is passed to the first function:

The state machine starts to execute as soon as I click on Start Execution. I can follow along and watch as execution flows from state to state:

I can visit the Lambda Console and see that my function ran four times as expected (I was pressed for time and didn’t bother to create four separate functions):

AWS Step Functions records complete information about each step and I can access it from the Step Console:

AWS Step Functions API
As I mentioned earlier, most of your interaction with AWS Step Functions will happen through the APIs. Here’s a quick overview of the principal functions:

  • CreateStateMachine – Create a new state machine, given a JSON description.
  • ListStateMachines – Get a list of state machines.
  • StartExecution – Run (asynchronously) a state machine.
  • DescribeExecution – Get information about an execution.
  • GetActivityTask – Poll for new tasks to run (used by long-running workers).

You could arrange to run a Lambda function every time a new object is uploaded to an S3 bucket. This function can then kick off a state machine execution by calling StartExecution. The state machine could (as an example) validate the image, generate multiple sizes and formats in parallel, check for particular types of content, and update a database entry.

The same functionality is also available from the AWS Command Line Interface (CLI).

Development Tools
You can use our new statelint gem to check your hand or machine-generated JSON for common errors including unreachable states and the omission of a terminal state.

Download it from the AWS GitHub repo ( it will also be available on RubyGems) and install it like this:

$ sudo gem install j2119-0.1.0.gem statelint-0.1.0.gem

Here’s what happens if you have a problem:

$ statelint my_state.json
2 errors:
 State Machine.States.Goodbye does not have required field "Next"
 No terminal state found in machine at State Machine.States

And if things look good:

$ statelint my_state.json
$

Available Now
AWS Step Functions is available now and you can start using it today in the US East (Northern Virginia), US East (Ohio), US West (Oregon), EU (Ireland), and Asia Pacific (Tokyo) Regions.

As part of the AWS Free Tier, you can perform up to 4,000 state transitions per month at no charge. After that, you pay $0.025 for ever 1,000 state transitions.

Jeff;