serverless-AWS

Example REST API using the serverless stack from AWS: Lambda, DynamoDB, SAM, API Gateway

• serverless-AWS
  • Available endpoints:
  • Prerequisites
  • How to deploy the API
    • SAM configuration
    • SAM deploy
  • Short code overview
    • dbManager.js
    • Template.yaml
  • Entities
    • Post
    • Comment
  • Integration Tests
  • Github Actions pipeline

Available endpoints:

Method	Resource
GET	/posts
GET	/posts/{postId}
POST	/posts
POST	/posts/{postId}/comments
PUT	/posts/{postId}
DELETE	/posts/{postId}
DELETE	/posts/{postId}/comments/{commentId}

Prerequisites

In order to deploy this lambda application into you AWS environment, you will first need:

• AWS account (educate, free tier or normal)
• SAM cli installed
• AWS credentials configured

How to deploy the API

SAM configuration

You can manually create this file or use the command sam deploy --guided to interactively create it.

version = 0.1
[default]
[default.deploy]
[default.deploy.parameters]
stack_name = "serverless-aws"
s3_bucket = "s3.cloudapps.codeurjc"
s3_prefix = "serverless-aws"
region = "us-east-1"
capabilities = "CAPABILITY_IAM"

Important information here is the S3 Bucket where your code will get packaged to and it's prefix. Also the region in where your API will get deployed, and where your DynamoDB is, please notice lines 4 to 6 in src/dbManager.js:

AWS.config.update({
    endpoint: "https://dynamodb.us-east-1.amazonaws.com"
});

SAM deploy

Once samconfig.toml is in place, you can already perform sam deploy and your lambda application sould get deployed in your AWS account. Thanks to the last line of the file template.yaml, the logs from deploy should at the very end print the prod url where the API is now available:

Value: !Sub "https://${ServerlessRestApi}.execute-api.${AWS::Region}.amazonaws.com/Prod/posts/"

Once deployed, feel free to use the provided Postman collection against the API.

Short code overview

The key parts are src/dbManager.js and template.yaml.

dbManager.js

This file first imports the node AWS sdk const AWS = require('aws-sdk') and creates a Dynamo DocumentClient const docClient = new AWS.DynamoDB.DocumentClient() to manage documents against the database on each lambda. Now retrieving a collection from a lambda would be as easy as:

const params = {
    TableName: 'posts'
};

return docClient.scan(params).promise();

A more complex example would be creating a comment within a Post comments collection:

const params = {
    TableName: 'posts',
    Key: {
        "postid": postid
    },
    UpdateExpression: 'set comments.#commentid = :comment',
    ExpressionAttributeNames: {
        "#commentid": commentid
    },
    ExpressionAttributeValues: {
        ":comment": comment,
    },
    ReturnValues: "UPDATED_NEW"
};
return docClient.update(params).promise();

Notice as well the parameter Returnalues where what the API will return after the action is carried out

Template.yaml

Defines a lambda function defining the events that will trigger this function, such as this piece of code:

lambdaGetPost:
  Type: Api
  Properties:
      Path: /posts/{postid}
      Method: GET

Will make a GET to the resource /posts/{postid} trigger our lambda application.

This template also defines one or more policies that this function needs. They will be appended to the default role for this function. This way:

Effect: Allow
Action:
    -   'dynamodb:Scan'
    -   'dynamodb:Query'
    -   'dynamodb:DeleteItem'
    -   'dynamodb:GetItem'
    -   'dynamodb:PutItem'
    -   'dynamodb:UpdateItem'

All these actions will be allowed over DynamoDB.

The second part of the yaml file, defines a DynamoDB table:

Type: 'AWS::DynamoDB::Table'
Properties:
    TableName: posts
    AttributeDefinitions:
        -   AttributeName: postid
            AttributeType: S
    KeySchema:
        -   AttributeName: postid
            KeyType: HASH
    ProvisionedThroughput:
        ReadCapacityUnits: 5
        WriteCapacityUnits: 5

Entities

Post

{
	"name": "Jack Nicholson",
	"nickname": "Nicky",
	"title": "My Joker was good too",
	"content": "Respect for Heath Ledger and Joaquin Phoenix",
	"comments": {}
}

Comment

{
	"nickname": "Random Internet Guy",
	"comment": "Here is Johnny!",
	"creationDate": "2019-11-26 10:15:55"
}

Integration Tests

Find inside directory src/integrationtests a straightforward postman collection, including test assertions, testing every endpoint and a main application flow:

1. Create a Post
2. Get all available Posts
3. Get a specific Post checking structure
4. Modify the Post's nickname
5. Get it again to check whether it was modified correctly
6. Add a Comment to the Post
7. Delete the Comment
8. Delete the Post

To run them, you have basically two options:

• Import the collection in Postman and run them manually
• Install Newman npm install -g newman and execute npm run test:integration

Github Actions pipeline

A very simple actions pipeline is provided in this project too. The file .github/workflows/ci.yml will create a pipeline which will trigger the postman collection automatically using newman against the production url for the api:

integration_tests:
    name: Run integration tests
    runs-on: ubuntu-16.04
    steps:
    - uses: actions/checkout@master
    - uses: actions/setup-node@v1
      with:
        node-version: '12.x'
    - name: Install Newman
      run: npm install -g newman
    - name: Integration Tests
      run: cd src && npm run test:integration