[AWS] SAM

AWS SAM (Serverless Application Model) is an open-source framework to define serverless applications using YAML.

Features

• SAM helps you to create serverless applications using simple YAML configuration.
• In SAM, you can use all CloudFormation features.
• SAM can use CodeDeploy to deploy Lambda functions.
  • Traffic Shift with aliases
  • PreTraffic and PostTraffic hooks

How it Works

1. You can provide the simplified instruction to define your application
   • Lambda function: AWS::Serverless::Function
   • API: AWS::Serverless::Api
   • DynamoDB: AWS::Serverless::SimpleTable
2. AWS SAM transforms the instructions into the fully detailed CloudFormation template.
3. AWS CloudFormation uses the transformed template to build the stack.

AWSTemplateFormatVersion : '2010-09-09'
Transform: AWS::Serverless-2021-07-11
Description: A hello world application.
Resources:
  HelloWorldFunction:
    Type: AWS::Serverless::Function
    Properties:
      Handler: main.handler
      Runtime: python3.9
      CodeUri: ./src

      AutoPublishAlias: live

      DeploymentPreferences:
        Type: Canary10Percent10Minutes # Canary, Linear, AllAtOnce
        Hooks:
          PreTraffic: !Ref PreTrafficLambdaFunc
          PostTraffic: !Ref PostTrafficLambdaFunc

AWS SAM CLI

You can use the AWS SAM CLI utility to test and deploy your application.

• SAM CLI launches a Docker container.
• You can use Cloud9 Environment – Linux 2 instance – to use the pre-installed SAM CLI.

cat /etc/os-release

sam --version

sam validate

Lambda Deployment – SAM & CodeDeploy

When you deploy Lamdba functions, SAM uses CodeDeploy under the hood. So you can leverage CodeDeploy functionalities using SAM when deploying Lambda functions.

• Traffic Shifting
• PreTraffic and PostTraffic hooks
• Automatic rollbacks using CloudWatch alarms

AutoPublishAlias

• Creates and publish a new version of a function when the new code is uploaded
• Update the alias to point the updated version of the Lambda function

DeploymentPreference

• Type
  • AllAtOnce, Linear, and Canary
• Alarms
  • alarms that can trigger rollback
• Hooks
  • PreTraffic
  • PostTraffic