sam-app

This is a sample project about AWS SAM on the BASE Development Team Blog.
Please visit the BASE Development Team Blog for more information.

.
├── Makefile                    <-- Make to automate build
├── README.md                   <-- This instructions file
├── hello-world                 <-- Source code for a lambda function
│   ├── main.go                 <-- Lambda function code
│   └── main_test.go            <-- Unit tests
└── template.yaml

Requirements

• AWS CLI already configured with Administrator permission
• Docker installed
• Golang
• SAM CLI - Install the SAM CLI

Setup process

Installing dependencies & building the target

In this example we use the built-in sam build to automatically download all the dependencies and package our build target.
Read more about SAM Build here

The sam build command is wrapped inside of the Makefile. To execute this simply run

make build

Local development

** Invoking function locally with dispatched event **

make local run

Invoking function locally through local API Gateway

make local up

If the previous command ran successfully you should now be able to hit the following local endpoint to invoke your function http://localhost:3000/hello

SAM CLI is used to emulate both Lambda and API Gateway locally and uses our template.yaml to understand how to bootstrap this environment (runtime, where the source code is, etc.) - The following excerpt is what the CLI will read in order to initialize an API and its routes:

...
Events:
    HelloWorld:
        Type: Api # More info about API Event Source: https://github.com/awslabs/serverless-application-model/blob/master/versions/2016-10-31.md#api
        Properties:
            Path: /hello
            Method: get

Packaging and deployment

AWS Lambda Golang runtime requires a flat folder with the executable generated on build step. SAM will use CodeUri property to know where to look up for the application:

...
    FirstFunction:
        Type: AWS::Serverless::Function
        Properties:
            CodeUri: hello_world/
            ...

To deploy your application for the first time, run the following in your shell:

make deploy dev

The command will package and deploy your application to AWS, with a series of prompts:

• Stack Name: The name of the stack to deploy to CloudFormation. This should be unique to your account and region, and a good starting point would be something matching your project name.
• AWS Region: The AWS region you want to deploy your app to.
• Confirm changes before deploy: If set to yes, any change sets will be shown to you before execution for manual review. If set to no, the AWS SAM CLI will automatically deploy application changes.
• Allow SAM CLI IAM role creation: Many AWS SAM templates, including this example, create AWS IAM roles required for the AWS Lambda function(s) included to access AWS services. By default, these are scoped down to minimum required permissions. To deploy an AWS CloudFormation stack which creates or modified IAM roles, the CAPABILITY_IAM value for capabilities must be provided. If permission isn't provided through this prompt, to deploy this example you must explicitly pass --capabilities CAPABILITY_IAM to the sam deploy command.
• Save arguments to samconfig.toml: If set to yes, your choices will be saved to a configuration file inside the project, so that in the future you can just re-run sam deploy without parameters to deploy changes to your application.

You can find your API Gateway Endpoint URL in the output values displayed after deployment.

Testing

We use testing package that is built-in in Golang and you can simply run the following command to run our tests:

make test

Appendix

Golang installation

Please ensure Go 1.x (where 'x' is the latest version) is installed as per the instructions on the official golang website: https://golang.org/doc/install

A quickstart way would be to use Homebrew, chocolatey or your linux package manager.

Homebrew (Mac)

Issue the following command from the terminal:

brew install golang

If it's already installed, run the following command to ensure it's the latest version:

brew update
brew upgrade golang

Chocolatey (Windows)

Issue the following command from the powershell:

choco install golang

If it's already installed, run the following command to ensure it's the latest version:

choco upgrade golang

Bringing to the next level

Here are a few ideas that you can use to get more acquainted as to how this overall process works:

• Create an additional API resource (e.g. /hello/{proxy+}) and return the name requested through this new path
• Update unit test to capture that
• Package & Deploy

Next, you can use the following resources to know more about beyond hello world samples and how others structure their Serverless applications:

• AWS Serverless Application Repository