How to Pass Variables from CodeBuildStep to a Stack in AWS CDK Pipeline

Learn how to pass variables effectively from CodeBuildStep to a LambdaStack in your CDK pipeline while avoiding infinite loops during deployment.
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Passing Variables from CodeBuildStep to Stack in AWS CDK Pipeline

When building a Continuous Deployment (CD) pipeline using AWS CDK, one common challenge developers face is effectively passing environment variables from a CodeBuildStep to various stages, particularly when deploying resources like an AWS Lambda function. In this guide, we will dive into a scenario where this process can lead to configuration issues, specifically an infinite deployment loop.

The Challenge

Imagine you have developed a basic CDK pipeline intended to automate the deployment of a Lambda function. As part of your pipeline, you want to:

Build the Lambda function, generating a zip file

Deploy the artifact to AWS CodeArtifact

Deploy the zip file to the Lambda function, reflecting the updated version

However, when trying to pass the extracted version number (referred to as LAMBDA_SNAPSHOT_VERSION_ID) from the CodeBuildStep to the LambdaStack, you encounter an infinite loop in the deployment process.

The Root Cause of the Problem

Solution to the Infinite Loop Issue

Step-by-Step Solution

Update Code to Use TreeMap:
Modify the method that creates your environment variable map so that it utilizes TreeMap. Here’s an updated version of the method:

[[See Video to Reveal this Text or Code Snippet]]

Utilize CDK Diff:
Incorporate cdk diff in your synthesis step to identify changes to the pipeline configuration. This will help troubleshoot potential issues before executing the deployments.

[[See Video to Reveal this Text or Code Snippet]]

Test Your Changes:
After incorporating the necessary changes, test your pipeline to ensure that it no longer enters an infinite loop and performs as expected.

Conclusion

If you still encounter issues or have questions about AWS CDK or CodeBuild, feel free to leave a comment below!