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Asked: 2024-09-21T17:08:08+05:30 In:

How can I implement a mechanism in AWS Step Functions to pause execution until a CloudFormation stack creation or update is completed?

anonymous user

Hey everyone,

I’ve been working with AWS Step Functions, and I’m trying to figure out the best way to create a mechanism that can pause execution while waiting for a CloudFormation stack to finish either its creation or update process. I want to ensure that my workflow does not proceed until the stack is fully set up or updated before moving on to the next step.

I’m considering various approaches, like using an external polling mechanism or leveraging AWS Lambda, but I’m not really sure what the best practice would be.

Has anyone else tackled this issue? What strategies have you found effective for synchronizing Step Functions with CloudFormation stack operations? Any tips or best practices would be greatly appreciated!

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    3 Answers

    1. anonymous user



      AWS Step Functions and CloudFormation Synchronization

      Synchronizing AWS Step Functions with CloudFormation

      Hello!

      I’ve faced a similar challenge when working with AWS Step Functions in conjunction with CloudFormation stacks. Here are a few approaches I’ve found helpful:

      1. Use AWS Lambda for Polling

      You can create a Lambda function that uses the AWS SDK to check the status of your CloudFormation stack. This function can be invoked within your Step Function state machine.

      Here’s a simple flow:

      • Invoke the Lambda function to start CloudFormation stack creation/update.
      • Use a “Task” state in your Step Function to invoke another Lambda function that checks the status of the stack.
      • The Lambda function can return the stack status, which you can then check in your Step Function. If the stack is still being created/updated, you can retry after a delay.

      2. Callback Mechanism Using Step Functions

      Another approach worth considering is using the Wait state in Step Functions along with a callback pattern. After you initiate the stack operation, you could have a “Wait” state that pauses execution for a defined interval before checking the status again.

      This can help prevent your workflow from proceeding too quickly and allow for a smoother synchronization process.

      3. Event-Driven Approach

      Lastly, consider an event-driven strategy using Amazon CloudWatch Events (or EventBridge). You can set up an event rule to trigger a Lambda function when the CloudFormation stack reaches a terminal state (CREATE_COMPLETE or UPDATE_COMPLETE). This function would notify your Step Function to continue its execution.

      Best Practices

      • Implement error handling in your Lambda functions to gracefully handle failures during polling.
      • Make use of exponential backoff in your polling to avoid overwhelming the CloudFormation API.
      • Keep your state machine design modular and avoid too many synchronous calls to keep the performance optimal.

      Each of these approaches has its pros and cons, and the best choice depends on your specific use case. Experiment with them and see which one fits best for your workflow. Good luck!


    2. anonymous user



      AW Step Functions and CloudFormation

      Re: AWS Step Functions and CloudFormation Synchronization

      Hey there!

      It sounds like you’re doing some interesting work with AWS Step Functions! I totally get how tricky it can be to pause execution while waiting for a CloudFormation stack to finish. Here are a few approaches that might help you:

      • Lambda with WaitForTaskToken: You can use an AWS Lambda function to create a custom resource in your CloudFormation stack. The Lambda function could call the GetStackStatus API to check the status of the stack and return it to the Step Function. You can pause your Step Function using a WaitForTaskToken to wait for the Lambda function to finish checking the stack status.
      • Polling Mechanism: Another method is to implement a polling mechanism where you periodically check the stack status at set intervals. You can achieve this by repeatedly invoking a Lambda function or using a Wait state in your Step Function to wait a few seconds before checking the status again.
      • Using CloudFormation Events: If you want to go a more event-driven route, you can set up an Amazon SNS topic that your CloudFormation stack can publish to when it is complete. Your Step Function can then start a Lambda function that listens to that SNS topic to trigger the next step once the stack creation or update is done.

      Each of these methods has its pros and cons, so it really depends on your specific use case and the complexity you’re comfortable managing. I hope this gives you some ideas to explore further!

      Good luck!


    3. anonymous user


      To synchronize AWS Step Functions with CloudFormation stack operations effectively, a reliable approach is to utilize the intrinsic capabilities of AWS services. One popular strategy is to use AWS Lambda in conjunction with Step Functions to check the status of the CloudFormation stack. You can create a Lambda function that polls the CloudFormation API to check the status of the stack during its creation or update. This Lambda function can be invoked by a Task State in your Step Function workflow, and with the success or failure status returned from the Lambda function, you can control the flow of the state machine, allowing it to only proceed once the CloudFormation update is complete.

      Another effective strategy involves using a combination of EventBridge and Step Functions. You can create an EventBridge rule that listens for CloudFormation stack events such as ‘CREATE_COMPLETE’ or ‘UPDATE_COMPLETE’ and use that to trigger your Step Functions workflow. This would eliminate the need for polling and provide a more event-driven approach, allowing your workflow to react when the stack is ready. By leveraging these AWS features, you can create a robust mechanism that ensures your Step Functions do not proceed until the CloudFormation operations are fully completed, ensuring synchronization and reducing potential race conditions.


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