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SAM

Links: 102 AWS DVA Index


SAM

  • It stands for Serverless Application Model
  • Framework for developing and deploying serverless applications
  • All the configuration is YAML code
  • Generate complex CloudFormation from simple SAM YAML file
  • Supports anything from CloudFormation: Outputs, Mappings, Parameters, Resources...
  • Only two commands to deploy to AWS
  • SAM can use CodeDeploy to deploy Lambda functions
  • SAM can help you to run Lambda, API Gateway, DynamoDB locally
  • SAM Deployment Process
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The template you write in SAM is converted to a CloudFormation template. Any time you see the keyword Transform in a template then it means it is a SAM template

Recipe

  • Transform Header indicates it's SAM template:
    • Transform: AWS::Serverless-2016-10-31
  • Write Code
    • AWS::Serverless::Function
    • AWS::Serverless::Api
    • AWS::Serverless::SimpleTable
  • Package & Deploy:
    • aws cloudformation package / sam package
    • aws cloudformation deploy / sam deploy

CLI Debugging

  • Locally build, test, and debug your serverless applications that are defined using AWS SAM templates
  • Provides a lambda-like execution environment locally
  • SAM CLI + AWS Toolkits => step-through and debug your code
  • AWS Toolkits: IDE plugins which allows you to build, test, debug, deploy, and invoke Lambda functions built using AWS SAM

SAM Policy Templates

  • List of templates to apply permissions to your Lambda Functions
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  • Important examples:
    • S3ReadPolicy: Gives read only permissions to objects in S3
    • SQSPollerPolicy: Allows to poll an SQS queue
    • DynamoDBCrudPolicy: CRUD
  • The idea is to focus on what you want to do rather than focusing on how to do it (like worrying about policies)

SAM & CodeDeploy

  • SAM framework natively uses CodeDeploy to update Lambda functions
  • Pre and Post traffic hooks features to validate deployment (before the traffic shift starts and after it ends)
  • Easy & automated rollback using CloudWatch Alarms

SAR (Serverless Application Repository)

  • Managed repository for serverless applications
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  • The applications are packaged using SAM
  • Build and publish applications that can be re-used by organisations
    • Can share publicly
    • Can share with specific AWS accounts
  • This prevents duplicate work, and just go straight to publishing
  • Application settings and behaviour can be customised using Environment variables

SAM Exam Summary

  • SAM is built on CloudFormation
  • SAM requires the Transform and Resources sections
  • Commands to know:
    • sam build: fetch dependencies and create local deployment artifacts
    • sam package: package and upload to Amazon S3, generate CF template
    • sam deploy: deploy to CloudFormation
  • SAM Policy templates for easy lAM policy definition
  • SAM is integrated with CodeDeploy to do deploy to Lambda aliases

Last updated: 2022-05-27