AWS - Serverless Web Application

Create table

See Create table DynamoDB

IAM Role Creation

The IAM role needs to grants to the Lambda function permission to:

• write logs to Amazon CloudWatch Logs
• to write items to a DynamoDB table.

Create Role:

• Create Role > Aws Service > Lambda > Next
• Permissions > AWSLambdaBasicExecutionRole > Next
• Create Role > RoleName

Selecting a role type automatically creates a trust policy for your role that allows AWS services to assume this role on your behalf. If you were creating this role using the CLI, AWS CloudFormation or another mechanism, you would specify a trust policy directly.

Role Policy:

• Select Role > Add Inline Policy
  • Choose a Service > DynamoDb
  • Choose a action > PutItem
  • Choose a resources > Add the Table ARN
  • Next
• Create Policy > Name: DynamoDBWriteAccess > Create

Lambda creation

• Console > Services > Lambda > Create a function
  • Options: Author from scratch
  • Name: RequestUnicorn
  • Runtime: Node
  • Role: Use an existing role
  • Create
• Scroll down to the Function code
  • Copy/Paste your code (For the demo requestUnicorn.js)
• Create a test
  • From the dropdown at the top of the page: Configure test events
  • Name: TestRequestEvent
  • Code:

{
    "path": "/ride",
    "httpMethod": "POST",
    "headers": {
        "Accept": "*/*",
        "Authorization": "eyJraWQiOiJLTzRVMWZs",
        "content-type": "application/json; charset=UTF-8"
    },
    "queryStringParameters": null,
    "pathParameters": null,
    "requestContext": {
        "authorizer": {
            "claims": {
                "cognito:username": "the_username"
            }
        }
    },
    "body": "{\"PickupLocation\":{\"Latitude\":47.6174755835663,\"Longitude\":-122.28837066650185}}"
}

• Click on the Test button. Response:

{
  "statusCode": 201,
  "body": "{\"RideId\":\"j09lHYJSAPWwS6k81qEg1Q\",\"Unicorn\":{\"Name\":\"Rocinante\",\"Color\":\"Yellow\",\"Gender\":\"Female\"},\"UnicornName\":\"Rocinante\",\"Eta\":\"30 seconds\",\"Rider\":\"the_username\"}",
  "headers": {
    "Access-Control-Allow-Origin": "*"
  }
}

RESTful APIs

Amazon API Gateway exposes the Lambda function and secure it using the Amazon Cognito user pool.

Request Browser code is in the ride.js file. It uses jQuery's ajax() method to make the remote http request.

Create API

• AWS Management Console> Services > API Gateway
• Create new API
  • Name: WildRydes
  • Endpoint Type: Edge optimized. Edge optimized are best for public services being accessed from the Internet. Regional endpoints are typically used for APIs that are accessed primarily from within the same AWS Region
  • Create
• Create a new Authorizer
  • Select the created API
  • Scroll Down to Authorizer
  • Create a new one
  • Select Incognito
  • Select the Region
  • Select the User pool
  • Token Source: Authorization
  • Create
• Create a new resources
  • Select the created API
  • Scroll down to Resources
  • Actions > Create Resources
    • Name: ride
    • Enable API Gateway CORS: Yes
    • Create
• Create a new HTTP method for the resources (ie HTTP request type: PUT, GET,…)
  • Select the created API
  • Scroll down to Resources
  • Select the Resources
  • Actions > Create a new Method
  • Select below the resources the POST method
  • Setup:
    • Integration Type: Lambda
    • Use Lambda Proxy integration: Check
    • Lambda function: RequestUnicorn or the ARN
• Resources Authorization:
  • Select a resource
  • Choose the Method Request card.
  • Pencil closed to Authorization
  • Select the authorizer: ie the Cognito User Pool
  • Click the ok mark
• Deploy API
  • Amazon API Gateway console
  • Select API
  • Actions > Deploy API
  • Stages: New Stage called prod
  • Note the Invoke URL: Example https://o2f6vh7cwf.execute-api.eu-central-1.amazonaws.com/prod. This is the API endpoint URL
  • Set the URL in the invokeUrl property of the config.js

Example:

window._config = {
    cognito: {
        userPoolId: 'eu-central-1_7l0D9CCvP', // PoolId e.g. us-east-2_uXboG5pAb
        userPoolClientId: '4rv21psdl35dsj3d1hhb5pug3p', // App clients Id e.g. 25ddkmj4v6hfsfvruhpfi7n4hv
        region: 'eu-central-1' // e.g. us-east-2
    },
    api: {
        invokeUrl: 'https://o2f6vh7cwf.execute-api.eu-central-1.amazonaws.com/prod' // e.g. https://rc7nyt4tql.execute-api.us-west-2.amazonaws.com/prod',
    }
};