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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