tmclaugh / aws-cfn-lambda-updater

AWS Lambda function to update Lambda functions via CloudFormation.

aws-cfn-lambda-updater

Lambda function to update other Lambda function when called via CloudFormation.

This repository contains two Lambda functions along with CloudFormation templates for each function.

• aws-cfn-lambda-updater: Function for updating an AWS Lambda function when triggered via AWS CLoudFormation.
  • deployable code: https://s3.amazonaws.com/straycat-dhs-org-straycat-lambda-deploys/aws-cfn-lambda-updater.zip
  • CloudFormation template: https://s3.amazonaws.com/straycat-dhs-org-straycat-lambda-deploys/aws-cfn-lambda-updater.json
• aws-cfn-lambda-updater-example-lambda: Simple “Hello World” function to demonstrate using aws-cfn-lambda-updater.
  • deployable code: https://s3.amazonaws.com/straycat-dhs-org-straycat-lambda-deploys/aws-cfn-lambda-updater-example-lambda.zip
  • CloudFormation template: https://s3.amazonaws.com/straycat-dhs-org-straycat-lambda-deploys/aws-cfn-lambda-updater-example-lambda.json

Deployment

Deploying Both stacks can be done by clicking on "Launch Stack" below.

• aws-cfn-lambda-updater:
• aws-cfn-lambda-updater-example-lambda:

Usage

To use aws-cfn-lambda-updater to update another Lambda function that is deployed via CloudFormation, add a resource similar to the following to your CloudFormation template. You’ll need to add parameters for LambdaName and S3Bucket.

"LambdaInvokeUpdater": {
  "Type": "Custom::LambdaUpdaterInvoke",
  "Properties": {
    "ServiceToken":{
      "Fn::ImportValue": {
        "Fn::Sub": "aws-cfn-lambda-updater-LambdaFunctionArn"
      }
    },
    "FunctionName": {
      "Ref": "LambdaName"
    },
    "S3Bucket": {
      "Ref": "S3Bucket"
    },
    "S3Key": {
      "Fn::Sub": "${LambdaName}.zip"
    }
  }
}

To ensure that the LambdaInvokeUpdater resource requires an update on each version, add a command like the following to your build process.

$ python -c "import json, sys; cfn=json.load(sys.stdin); cfn['Resources']['LambdaInvokeUpdater']['Properties']['CodeSha256'] = '$(openssl dgst -binary -sha256 dist/aws-cfn-lambda-updater.zip | openssl base64)'; json.dump(cfn, sys.stdout, indent=2)" < dist/aws-cfn-lambda-updater-example-lambda.json > dist/aws-cfn-lambda-updater-example-lambda.json.new; mv dist/aws-cfn-lambda-updater-example-lambda.json{.new,}

See this repository’s .travis.yml for an example in practice.