sam-koi-api

Small API powered by AWS Serverless Application

.
├── README.md                   <-- This instructions file
├── koi-api                      <-- Source code for a lambda function
│   ├── app.js                  <-- Lambda function code
│   ├── package.json            <-- NodeJS dependencies
│   ├── lib                     <-- Libs
│   │    ├── config.js          <-- Handle configuration (can use dotenv)
│   │    ├── repository.js      <-- Handle DynmaoDB integration           
│   │    └── router.js          <-- Handle lambda event and content and return an http responses
│   └── tests                   <-- Unit tests
│       └── unit
│           └── test_handler.js
├── sam-iam.json               <-- IAM Policy statement needed for the user or service to bootstrap the app
├── swagger.yaml               <-- Swagger API specification for api-gateway
└── template.yaml               <-- SAM template

Requirements

• AWS CLI already configured with Administrator permission
• NodeJS 8.10+ installed
• Docker installed

Setup process

Building the project

AWS Lambda requires a flat folder with the application as well as its dependencies in a node_modules folder. When you make changes to your source code or dependency manifest, run the following command to build your project local testing and deployment:

sam build

If your dependencies contain native modules that need to be compiled specifically for the operating system running on AWS Lambda, use this command to build inside a Lambda-like Docker container instead:

sam build --use-container

By default, this command writes built artifacts to .aws-sam/build folder.

Local development

Invoking function locally through local API Gateway

sam local start-api

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

Packaging and deployment

AWS Lambda NodeJS runtime requires a flat folder with all dependencies including the application. SAM will use CodeUri property to know where to look up for both application and dependencies:

...
    FirstFunction:
        Type: AWS::Serverless::Function
        Properties:
            CodeUri: koi-api/
            ...

Firstly, we need a S3 bucket where we can upload our Lambda functions packaged as ZIP before we deploy anything - If you don't have a S3 bucket to store code artifacts then this is a good time to create one:

aws s3 mb s3://BUCKET_NAME

Next, run the following command to package our Lambda function to S3:

sam package \
    --template-file template.yaml \
    --output-template-file packaged.yaml \
    --s3-bucket REPLACE_THIS_WITH_YOUR_S3_BUCKET_NAME

Next, copy the swagger spec file so Cloudfomation will parse it correctly and associate with the Lambda:

aws s3 cp swagger.yaml s3://REPLACE_THIS_WITH_YOUR_S3_BUCKET_NAME

Next, the following command will create a Cloudformation Stack and deploy your SAM resources.

sam deploy \
    --template-file packaged.yaml \
    --stack-name sam-app \
    --capabilities CAPABILITY_IAM

See Serverless Application Model (SAM) HOWTO Guide for more details in how to get started.

After deployment is complete you can run the following command to retrieve the API Gateway Endpoint URL:

aws cloudformation describe-stacks \
    --stack-name sam-app \
    --query 'Stacks[].Outputs'

Testing

We use mocha for testing our code and it is already added in package.json under scripts, so that we can simply run the following command to run our tests:

cd koi-api
npm install
npm run test

Appendix

AWS CLI commands

AWS CLI commands to package, deploy and describe outputs defined within the cloudformation stack:

sam package \
    --template-file template.yaml \
    --output-template-file packaged.yaml \
    --s3-bucket REPLACE_THIS_WITH_YOUR_S3_BUCKET_NAME

sam deploy \
    --template-file packaged.yaml \
    --stack-name YOUR_STACK_NAME \
    --capabilities CAPABILITY_IAM \
    --parameter-overrides MyParameterSample=MySampleValue

aws cloudformation describe-stacks \
    --stack-name YOUR_STACK_NAME --query 'Stacks[].Outputs'

For help, you can use the following resources to know more about how others structure Serverless applications:

• AWS Serverless Application Repository

Pricing of used resources

Free tier

https://aws.amazon.com/free/

• Lambda:
• DynamoDB: 25g data; 1G output 12 months Pricing
• ApiGateway: 3,50 per Millions requests 12 months Pricing
• Cognito: 50000 Monthly Active Users always Pricing
• CloudWatch: 5g always Pricing
• Bandwidth: 15g 12 months