AWS SAM - Serverless Application Model

• It is a framework for developing and deploying serverless applications
• All the configurations for SAM are stored in YAML code
• SAML cli generates complex CloudFormation templates from SAM YAML code
• Supports anything from CloudFormation: Outputs, Mappings, Parameters, Resources, etc.
• SAM can be used with CodeDeploy to deploy Lambda functions
• SAM can help use to run Lambda, API Gateway and DynamoDB locally

Recipe

• SAM YAML template contains the following headers:
  • Transform: 'AWS::Serverless-2016-10-31
  • The meaning of this is that CloudFormation knows how to transform this YAML template into CloudFormation template
• Other resources:
  • AWS::Serverless::Function
  • AWS::Serverless::Api - API Gateway
  • AWS::Serverless::SimpleTable - DynamoDB table
• Package and deploy SAM applications:
  • aws cloudformation package / sam package
  • aws cloudformation deploy / sam deploy

SAM CLI

• To run a SAM application locally we can use the SAM cli
• It helps us locally build and debug serverless applications
• SAM has support for IDEs: VSCOde, JetBrains Intellij/PyCharm, AWS Cloud9, etc.
• AWS Toolkit: IDE plugins which allows us to build, test, debug and deploy Lambda functions using AWS SAM

SAM CLI Commands

1. Download a sample application

    sam init --runtime java11
   

2. Build the application

    sam build
   

3. Invoke function locally

    sam local invoke <function-name> -e event.json
    sam local start-api
   

4. Package the application

    sam package --output-template packaged.yaml --s3-bucket <bucket-name> --region us-east-2 --profile aws-devops
   

5. Deploy the application

    sam deploy --template-file packaged.yaml --capabilities CAPABILITY_IAM --stack-name <stack-name> --region us-east-2 --profile aws-devops
   

SAM with CodeDeploy

• SAM framework natively uses CodeDeploy to update/deploy Lambda functions
• CodeDeploy will leverage the Traffic Shifting feature using Lambda aliases
• Pre and Post traffic hooks can be defined to validate deployment
• Automated rollbacks are supported with CloudWatch Alarms
• SAM with CodeDeploy YAML configuration:
  • AutoPublishAlias:
    • Detects when new code is being deployed
    • Creates and publishes an updated version of the function with the latest code
    • Points the alias to the updated version of the Lambda function
  • DeploymentPreference: Canary, Linear, AllAtOnce
  • Alarms:
    • Can trigger a rollback
  • Hooks:
    • Pre and post traffic shifting Lambda functions used to test the deployment