Serverless Function Version Plugin

A Serverless plugin to use a function version within an environment variable.

Motivation

There are circumstances where you may need to reference a function's version within an environment variable. For example, when using CodeDeploy, the pre/post-traffic Lambdas need to know which version of a function to test.

Serverless produces a AWS::Lambda::Version resource - which contains the Lambda version reference - using a dynamically generated name. This makes it impossible to reference this resource at configuration time within the Serverless config file.

This plugin solves the problem by finding the AWS::Lambda::Version resource after the CloudFormation template has been generated, then including a reference to the resource as the variable-value.

Installation

npm install --save-dev serverless-function-version

Add the plugin to serverless.yml:

plugins:
  - serverless-function-version

Note: Node 10.x or higher runtime required.

Usage

Inside your Serverless config, include this plugin.

plugins:
  - serverless-function-version    

Then you can use the following syntax to get the function version:

• ${functionVersionArn:...} is replaced with the full ARN of the function, including the version number
• ${functionVersion:...} is replaced with just the version number

# serverless.yml

 functions: 
   getPhone: {...}, # This is the function we want to reference
   getPhonePreDeployHook:
    handler: 'src/getPhone/hooks.pre'
    environment:
      FUNCTION_TO_TEST: '${functionVersionArn:GetPhoneLambdaFunction}', # This is converted to the ARN including the VERSION at deployment-time
      FUNCTION_VERSION_ONLY: '${functionVersion:GetPhoneLambdaFunction}'

NOTE: The ${functionVersion*} variables can only be used within the provider.environment section, or within a function's environment section.