Skip to content

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 local start-lambda
      • Starts a local endpoint that emulates AWS Lambda.
      • We can do automated tests against this endpoint.
    • sam local invoke
      • Invoke Lambda function with payload once and quit after invocation completes.
      • Helpful for generating test cases

  • SAM Deployment Process

    • attachments/Pasted image 20220527111606.jpg
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: Lambda
    • AWS::Serverless::Api: API Gateway
    • AWS::Serverless::SimpleTable: DynamoDB
    • AWS::Serverless::Application: SAR
  • Package & Deploy:
    • aws cloudformation package / sam package
      • The command uploads local artifacts to an S3 bucket.
    • 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
    • attachments/Pasted image 20220527121444.jpg
  • 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
    • attachments/Pasted image 20220527131012.jpg
  • 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 section in its template.
  • Commands to know:
    • sam init: initialises a serverless application with an AWS SAM template
    • 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: 2023-03-01