Marcel Krčah

Parameterize AWS Lambda with SSM Param Store

Published on , in #aws, #cloudformation, #serverless

Here's an example on how to add a Slack channel and a webhook url from SSM Parameter Store into AWS Lambda environment variable:

# cloudformation template
AWSTemplateFormatVersion: '2010-09-09'
Transform: AWS::Serverless-2016-10-31

Parameters:
	SlackWebhookUrl:
	  Type: AWS::SSM::Parameter::Value<String>
	  Default: '/services/Slack/incomingWebhookUrl'

	SlackChannel:
	  Type: AWS::SSM::Parameter::Value<String>
	  Default: '/services/Slack/channels/exampleChannel'

Resources:
  ExampleLambda:
    Type: AWS::Serverless::Function
    Properties:
      Environment:
        Variables:
          SLACK_WEBHOOK_URL: !Ref SlackWebhookUrl
          SLACK_CHANNEL: !Ref SlackChannel
	# ... CodeUri, etc...

in Lambda, read from env vars:

// in the Lambda handler (Typescript example)
const slack = Slack({
  url: process.env.SLACK_WEBHOOK_URL,
  channel: process.env.SLACK_CHANNEL,
})

For local develoment and sam local invoke, use env-vars option or supply env vars to Lambda via bash:

# content of dev-env.sh
# better not in version control, because it contains secrets
export SLACK_CHANNEL=slack-integration-test
export SLACK_WEBHOOK_URL=<your-slack-url>

followed by:

$ source dev-env.sh && sam local invoke Main #...remaining sam args

This blog is written by Marcel Krcah, an independent consultant for product-oriented software engineering. If you like what you read, sign up for my newsletter