AWS SAM solution to automatically invalidate content in a cloudfront distribution based on S3 update events
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README.md

aws-cloudfront-auto-invalidator

This is a small Lambda function (packaged somewhat with AWS SAM) to auto-invalidate content in Cloudfront when the underlying S3 origin content changes.

Requirements

  • AWS CLI (configured with at least one profile)
  • AWS SAM CLI
  • Existing S3 bucket to store SAM Lambda code
  • Existing S3 bucket and Cloudfront distribution

Deploying

Invoke the deploy.sh script in the root of the project as follows:

deploy.sh ALL|NEW_SUB <bucket for lambda code> <origin bucket> <AWS CLI profile name>

If ALL is specified as the first argument, the function will be packaged, deployed and a new event subscription will be created for the specified origin bucket. If NEW_SUB is supplied, only a new event subscription from an origin bucket will be added (ie. use this to subscribe multiple buckets to the single function)

Deployment Notes

Ideally, all of this solution would be a small, self-contained SAM application. But due to this issue, SAM cannot subscribe events to pre-existing buckets. Therefore, the deploy script has to add the Lambda permissions and S3 event subscription after the function has been created. This is all performed using the AWS CLI in the deploy.sh script.

Want to monitor multiple buckets? Just run deploy.sh with a different origin bucket (parameter 2). You'll get a different event subscription to the Lambda function.

Running locally

The function can be executed locally using the SAM CLI and the SampleEvent.json in the project. You will need Docker installed to enable local execution via SAM

sam local invoke --event SampleEvent.json

This will invoke your function and pass it the contents of SampleEvent.json. You will need to modify SampleEvent.json to represent a valid S3 bucket.