AWS Certified Developer Associate DVA-C01

20 AWS Serverless Application Model (SAM)

Table of Contents

• 20 AWS Serverless Application Model (SAM)
  • Table of Contents
  • AWS SAM
    • What it Looks Like
    • SAM Deployment
    • SAM Policy Templates
    • SAM with CodeDeploy
    • Summary
    • Console

AWS SAM

• serverless app model (sam)
• framework for developing and deploying serverless apps
  • all config in yaml
  • generate complex cloudformation from simple SAM YAML file
• supports anything from cloudformation
  • outputs, mappings, params, res etc.
• only 2 commands to deploy to aws
• sam can use codedeploy to deploy lambda funcs
  • sam can help you run lambda, api gateway, dynamodb locally
    • dont need to deploy lambda func to test it

What it Looks Like

• transform header indicating SAM template
  • Transform: 'AWS::Serverless-2016-10-31'
• write code
  • AWS::Serverless::Function
    • lambda
  • AWS::Serverless::Api
    • api gateway
  • AWS:Serverless::SimpleTable
    • dynamodb
• package and deploy
  • aws cloudformation package / sam package
  • aws cloudformation deploy / sam deploy

SAM Deployment

• aws cloudformation package
  • upload code zip file to s3
  • also transforms sam template into cloudformation template
  • generated templates will have a reference to s3
• aws cloudformation deploy
  • create and execute a change set
    • change set is figuring out how cloudformation shld take its existing state and move it to the next state based on modifications generated
  • cloudformation then applies it to our stack
    • stack may comprise of all services

SAM Policy Templates

• list of templates to apply perms to your lambda funcs
  • full list here
• important examples
  • S3ReadPolicy
    • gives read only perms to objs in s3
  • SQSPollerPolicy
    • allows to poll on sqs queue
  • DynamoDBCrudPolicy
    • create read update delete

• instead of creating iam role, attach policy in sam template instead

SAM with CodeDeploy

• sam framework natively uses codedeploy to update lambda functions
• leverage traffic shifting feature using aliases
• can also define pre and post traffic hooks features to validate deployment
  • before traffic shift starts and after it ends
• easy & automated rollback using cloudwatch alarms

• trigger deployment in codedeploy
  • runs pre traffic hook test using another lambda func
    • optional
  • do traffic shifting with alias
  • then monitor cloudwatch alarm
    • optional
    • ensure everything goes well during deployment
  • once deployment and traffic shifting done, run post-traffic hook lambda func
    • also optional
    • runs some tests on your alias
  • if everything goes well, v1 func of alias goes away
    • only left with v2

Summary

• sam is built on cloudformation
• sam requires Transform and Resources section
• 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 iam policy definition
• sam is integrated with codedeploy to do deploy to lambda aliases

Console

• https://docs.aws.amazon.com/serverless-application-model/latest/developerguide/serverless-sam-cli-install-windows.html
  • follow this
  • windows just download a sam installer
  • use brew for mac and linux

Init Project

• use sam init to generate a sam template for your specific runtime
  • but can also create from scratch on your own

• can go to sam examples github for dummy code
  • https://github.com/aws/serverless-application-model

• example template yaml file
  • Transform means sam template
  • resource list
    • 1st res is function
      • handler shld be <file name>.<function name>
    • codeuri shld point to dir with the code

• create cli commands to generate your transformed cloudformation template
  • first create s3 bucket
  • next upload code and do transformation from aws cloudformation package
    • can also use sam package since sam is just shorthand for aws cloudformation

• generated template
  • codeuri now points to s3
    
• running package will also output a sample deploy cli command
  

• failed as didnt add CAPABILITY_IAM into your cli cmd

• once deployed, can go to cloudformation to check your stack out

Adding API Gateway

• look for api gateway in the examples github for ref

• example lambda func for api gateway demo

• add events segment in lambda func to create new api
  • func is invoked everytime a get req is called to /hello
• rerun your cloudformation commands to create the new api gateway

• more resources created for your cloudformation
  • like api gateway and iam roles

Adding DynamoDB

• look for dynamodb example in github
  • actually prev api gateway example alr used dynamodb so we'll just use that

• example lambda func for adding of dynamodb
  • get region from os environment vars

• read doc for full list of properties u can pass into your simpletable segment
  • set provisioned throughput to save costs for this demo

• add your simpletable section in the yaml file

• can add env vars in your yaml template
  • table name refs the simpletable created
  • region refs a pseudo param AWS::Region

• rmb to add iam policy to your func
  • this basically gives a dynamodbcrudpolicy with ref to the table created to your lambda func

• sample function scans the dynamodb and returns it

CloudFormation Designer and App Repository

• can see details of what was created in cloudformation from viewing the stack
  • pic above shows the template code

• can go actions > view designer

• high lvl view of what was created

• also when creating your lambda func, u have option to use aws serverless app repo
  • is basically sam templates created by a lot of people
    • can search through

SAM with CodeDeploy

• using sam hello world python example

• codeploy yaml to be integrated with your template yaml

• add AutoPublishAlias in your lambda func section in template yaml
  • create new alias "live"
• also deployment pref specific canary 10% 10 mins
  • 10% of traffic go to new ver for 10mins then shift 100%

• can also use sam deploy --guided instead of package and deploy
  • run sam build before

• live alias created

• can view codedeploy traffic shift from codedeploy console

tags: AWS Developer Associate Notes