How to create a new version of a Lambda function using CloudFormation?

Question

I\'m trying to create a new version of a Lambda function using CloudFormation.

I want to have multiple versions of the same Lambda function so that I can (a) point a

Answer 1

This is a bit of a hack, and depends on using gitlab-ci (or something similar), but I find passing the commit hash into a cloudformation template (via the template's parameters) very useful.

(It's a bit like @Jerry 's answer, but using the commit hash.)

In this case you could do something like:

Have a parameter in your template for the commit hash, e.g.:

AWSTemplateFormatVersion: '2010-09-09'
Description: Template for Lambda Sample.
Parameters:
  ciCommitSha:
    Type: String
  s3Bucket:
    Type: String
  ...

You can then reference this in the lambda resource, like this:

  CFNLambda:
    Type: AWS::Lambda::Function
    Properties:
      FunctionName: cfn_trigger_fn
      Description: lambda which gets triggered by cloudformation
      Runtime: python3.7
      Code:
        S3Bucket: !Ref s3Bucket
        S3Key: !Join [ ".", [ !Ref ciCommitSha, "zip"]]
      Handler: function.handler
      ...

Your ci pipeline then needs to look something like (assuming you call your cloudformation template stack-template.yaml):

variables:
  REGION: us-east-1
  S3_BUCKET_NAME: my-bucket

stages:
 - build
 - push
 - deploy

build-package:
  stage: build
  script:
    - some code to produce a deployment package called function.zip
  artifacts:
    name: deployment_package
    paths:
      - function.zip


push-code:
  stage: push
  script:
    - aws s3 cp function.zip s3://$S3_BUCKET_NAME/$CI_COMMIT_SHA.zip

deploy-trigger-stack:
  stage: deploy
  script: 
      - aws cloudformation deploy
            --template-file stack-template.yaml
            --stack-name my-stack
            --region $REGION
            --no-fail-on-empty-changeset
            --capabilities CAPABILITY_NAMED_IAM
            --parameter-overrides
            ciCommitSha=$CI_COMMIT_SHA
            s3Bucket=$S3_BUCKET_NAME

You can use this technique for triggering cfn-init on EC2 metadata as well..