AWS SAM Basics

Basic configuration and application deployment using AWS SAM

AWS SAM

Serverless Application Model (SAM) is an extension to Cloudformation and used to define serverless applications. It provides a simplified syntax for defining resources like lambda functions, APIs, storages, permissions and integration between them. Allows with minimum lines configure a ready to go POC of application.

Boilerplate code expansion and transformation hapens during deployment process, SAM transforms it’s syntax into AWS CloudFormation one.

SAM template

Example template with s3 bucket as resource to be created in scope of this app.

AWSTemplateFormatVersion: "2010-09-09"
Transform: AWS::Serverless-2016-10-31
Description: >
   App01

   SAM basics   

Parameters:
  Env:
    Type: String
    Description: "Logical environment like dev, test, prod etc"
    Default: dev

Resources:
  AppBucket:
    Type: "AWS::S3::Bucket"
    Properties:
      BucketName: !Sub ${Env}-app01

SAM guided configuration

SAM can perform deployment through configuration flow with multiple questions before deploying the app. Resulting config can be saved for future reuse.

Guided flow

SAM Guided flow:

Resulting config after guide

version = 0.1
[dev]
[dev.deploy]
[dev.deploy.parameters]
stack_name = "app01"
s3_bucket = "aws-sam-cli-managed-default-samclisourcebucket-1f82bz09qi9s4"
s3_prefix = "app01"
region = "eu-west-1"
confirm_changeset = true
capabilities = "CAPABILITY_IAM"
parameter_overrides = "Env=\"dev\""
Notes

There were no deployment bucket so SAM created one:

aws-sam-cli-managed-default-samclisourcebucket-1f82bz09qi9s4

To make SAM use defferent bucket s3_bucket parameter should be changed in the configuration or passed dusing guided deployment stage.

SAM bucket after deployment

Name contains a generated segment to make it unique for collision avoiding

SAM s3 bucket:

Bucket contains a “folder” dedicated to application SAM has deployed

SAM s3 bucket:

Application “folder” contains app template

SAM s3 bucket:

SAM Cloudformation stack

Aside from creating a deployment bucket, SAM has it own stack deployed also.

SAM cloudformation stack:

With resource like s3 bucket SAM created, and policy for that bucket

SAM cloudformation resources:

SAM custom configuration

Start from creating custom s3 bucket SAM will use for future deployments

aws s3 mb s3://basicappdeployment --region eu-west-1

Example configuration for deployment to different environments like dev, test

version = 0.1
[dev]
[dev.deploy]
[dev.deploy.parameters]
stack_name = "dev-app01"
s3_bucket = "basicappdeployment"
s3_prefix = "dev-app01"
region = "eu-west-1"
confirm_changeset = true
capabilities = "CAPABILITY_NAMED_IAM"
parameter_overrides = "Env=\"dev\""

[test]
[test.deploy]
[test.deploy.parameters]
stack_name = "test-app01"
s3_bucket = "basicappdeployment"
s3_prefix = "test-app01"
region = "eu-west-1"
confirm_changeset = true
capabilities = "CAPABILITY_NAMED_IAM"
parameter_overrides = "Env=\"test\""
Notes

In order to disable configrmation for change set - remove or set to false confirm_changeset parameter

SAM deploy with custom config

Deployment using specific profile and logical environment (dev, test etc).

sam deploy --profile default --config-env dev --no-fail-on-empty-changeset
Notes

When deploynig using customly created s3 bucket SAM does not create a dedicated cloudformation stack.

Conclusions

Nice tool, easy to use, configure and control