HackMDAWS Certified Developer Associate DVA-C01
20 AWS Serverless Application Model (SAM)
Table of Contents
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
- sam can help you run lambda, api gateway, dynamodb locally
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 packageaws 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
- create and execute a change set
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
- runs pre traffic hook test using another lambda func
Summary
- sam is built on cloudformation
- sam requires
TransformandResourcessection - 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 initto 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
- example template yaml file
Transformmeans sam template- resource list
- 1st res is function
- handler shld be
<file name>.<function name>
- handler shld be
- codeuri shld point to dir with the code
- 1st res is function
- 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 packagesince sam is just shorthand for aws cloudformation
- can also use
- generated template
- codeuri now points to s3
- codeuri now points to s3
- running package will also output a sample deploy cli command
- failed as didnt add
CAPABILITY_IAMinto 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
- is basically sam templates created by a lot of people
SAM with CodeDeploy
- using sam hello world python example
- codeploy yaml to be integrated with your template yaml
- add
AutoPublishAliasin 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 --guidedinstead of package and deploy- run
sam buildbefore
- run
- live alias created
- can view codedeploy traffic shift from codedeploy console
