/Serveless-microservice-architecture

Serverless Architecture on AWS

Lab Overview And High Level Design

Let's start with the High Level Design. High Level Design An Amazon API Gateway is a collection of resources and methods. For this tutorial, you create one resource (DynamoDBManager) and define one method (POST) on it. The method is backed by a Lambda function (LambdaFunctionOverHttps). That is, when you call the API through an HTTPS endpoint, Amazon API Gateway invokes the Lambda function.

The POST method on the DynamoDBManager resource supports the following DynamoDB operations:

  • Create, update, and delete an item.
  • Read an item.
  • Scan an item.
  • Other operations (echo, ping), not related to DynamoDB, that you can use for testing.

The request payload you send in the POST request identifies the DynamoDB operation and provides necessary data. For example:

The following is a sample request payload for a DynamoDB create item operation:

{
    "operation": "create",
    "tableName": "lambda-apigateway",
    "payload": {
        "Item": {
            "id": "1",
            "name": "Bob"
        }
    }
}

The following is a sample request payload for a DynamoDB read item operation:

{
    "operation": "read",
    "tableName": "lambda-apigateway",
    "payload": {
        "Key": {
            "id": "1"
        }
    }
}

Setup

Create Lambda IAM Role

Create the execution role that gives your function permission to access AWS resources.

To create an execution role

  1. Open the roles page in the IAM console.
  2. Choose Create role.
  3. Create a role with the following properties.
    • Trusted entity – Lambda.
    • Role name – lambda-apigateway-role.
    • Permissions – Custom policy with permission to DynamoDB and CloudWatch Logs. This custom policy has the permissions that the function needs to write data to DynamoDB and upload logs.
    {
"Version": "2012-10-17",
"Statement": [
{
  "Sid": "Stmt1428341300017",
  "Action": [
    "dynamodb:DeleteItem",
    "dynamodb:GetItem",
    "dynamodb:PutItem",
    "dynamodb:Query",
    "dynamodb:Scan",
    "dynamodb:UpdateItem"
  ],
  "Effect": "Allow",
  "Resource": "*"
},
{
  "Sid": "",
  "Resource": "*",
  "Action": [
    "logs:CreateLogGroup",
    "logs:CreateLogStream",
    "logs:PutLogEvents"
  ],
  "Effect": "Allow"
}
]
}

Create Lambda Function

To create the function

  1. Click "Create function" in AWS Lambda Console

Create function

  1. Select "Author from scratch". Use name LambdaFunctionOverHttps , select Python 3.7 as Runtime. Under Permissions, select "Use an existing role", and select lambda-apigateway-role that we created, from the drop down

  2. Click "Create function"

Lambda basic information

  1. Replace the boilerplate coding with the following code snippet and click "Save"

Example Python Code

from __future__ import print_function

import boto3
import json

print('Loading function')


def lambda_handler(event, context):
    '''Provide an event that contains the following keys:

      - operation: one of the operations in the operations dict below
      - tableName: required for operations that interact with DynamoDB
      - payload: a parameter to pass to the operation being performed
    '''
    #print("Received event: " + json.dumps(event, indent=2))

    operation = event['operation']

    if 'tableName' in event:
        dynamo = boto3.resource('dynamodb').Table(event['tableName'])

    operations = {
        'create': lambda x: dynamo.put_item(**x),
        'read': lambda x: dynamo.get_item(**x),
        'update': lambda x: dynamo.update_item(**x),
        'delete': lambda x: dynamo.delete_item(**x),
        'list': lambda x: dynamo.scan(**x),
        'echo': lambda x: x,
        'ping': lambda x: 'pong'
    }

    if operation in operations:
        return operations[operation](event.get('payload'))
    else:
        raise ValueError('Unrecognized operation "{}"'.format(operation))

Lambda Code

Test Lambda Function

Let's test our newly created function. We haven't created DynamoDB and the API yet, so we'll do a sample echo operation. The function should output whatever input we pass.

  1. Click the arrow on "Select a test event" and click "Configure test events"

Configure test events

  1. Paste the following JSON into the event. The field "operation" dictates what the lambda function will perform. In this case, it'd simply return the payload from input event as output. Click "Create" to save
{
    "operation": "echo",
    "payload": {
        "somekey1": "somevalue1",
        "somekey2": "somevalue2"
    }
}

Save test event

  1. Click "Test", and it will execute the test event. You should see the output in the console

Execute test event

We're all set to create DynamoDB table and an API using our lambda as backend!

Create DynamoDB Table

Create the DynamoDB table that the Lambda function uses.

To create a DynamoDB table

  1. Open the DynamoDB console.
  2. Choose Create table.
  3. Create a table with the following settings.
    • Table name – lambda-apigateway
    • Primary key – id (string)
  4. Choose Create.

create DynamoDB table

Create API

To create the API

  1. Go to API Gateway console
  2. Click Create API

create API

  1. Scroll down and select "Build" for REST API

Build REST API

  1. Give the API name as "DynamoDBOperations", keep everything as is, click "Create API"

Create REST API

  1. Each API is collection of resources and methods that are integrated with backend HTTP endpoints, Lambda functions, or other AWS services. Typically, API resources are organized in a resource tree according to the application logic. At this time you only have the root resource, but let's add a resource next

Click "Actions", then click "Create Resource"

Create API resource

  1. Input "DynamoDBManager" in the Resource Name, Resource Path will get populated. Click "Create Resource"

Create resource

  1. Let's create a POST Method for our API. With the "/dynamodbmanager" resource selected, Click "Actions" again and click "Create Method".

Create resource method

  1. Select "POST" from drop down , then click checkmark

Create resource method

  1. The integration will come up automatically with "Lambda Function" option selected. Select "LambdaFunctionOverHttps" function that we created earlier. As you start typing the name, your function name will show up.Select and click "Save". A popup window will come up to add resource policy to the lambda to be invoked by this API. Click "Ok"

Create lambda integration

Our API-Lambda integration is done!

Deploy the API

In this step, you deploy the API that you created to a stage called prod.

  1. Click "Actions", select "Deploy API"

Deploy API

  1. Now it is going to ask you about a stage. Select "[New Stage]" for "Deployment stage". Give "Prod" as "Stage name". Click "Deploy"

Deploy API to Prod Stage

Adding API Key for additional security

  1. CLick on API Keys on the right menu bar. Click "Create API Key"

  2. Enter the name "Lambda-key". Select auto-generate and click "Save" Create Api key

  3. Copy the API-Key. This will be used later

  4. Click on "Usage Plans" on the right menu bar. This will allow you to define acceptable throttle and burst request rate that the API can handle without breaking down.Click "Create Usage Plan"

Usage Plan

  1. Enter name "Lambda-dynamoDB-usageplan". Turn on Throttling. Enter rate "100" per second and burst "20" per second. Click "Create Usage Plan" Create Usage Plan

  2. Open 'Lambda-dynamoDB-usageplan'. Click on "Add Stage" Add API to Usage Plan

  3. Select "DynamoDBOperations" APi and "Prod" Stage. Click "Add to usage plan". Add API to Usage Plan

  4. Now, we shall attach our API key to the usage plan. Open Lambda-key API key and click on "Add to Usage plan". Select the "Lambda-dynamodb-usageplan" from the dropdown list. Click Save Add key to Usage Plan

  5. Go to API and click Deploy API once again to commit all changes to API.

  6. We're all set to run our solution! To invoke our API endpoint, we need the endpoint url. In the "Stages" screen, expand the stage "Prod", select "POST" method, and copy the "Invoke URL" from screen

Copy Invoke Url

Running our solution

  1. The Lambda function supports using the create operation to create an item in your DynamoDB table. To request this operation, use the following JSON:
{
    "operation": "create",
    "tableName": "lambda-apigateway",
    "payload": {
        "Item": {
            "id": "1234ABCD",
            "number": 5
        }
    }
}
  1. To execute our API go to https://reqbin.com/. Paste the API invoke URL. Under content select "Json" and paste the above code. Under authorization, select "no-auth". Then, go to "Headers" and type x-api-key: (and paste the api key)

Post API Request Post API Request

A successful post will return a "status code: 200"

  1. To validate that the item is indeed inserted into DynamoDB table, go to Dynamo console, select "lambda-apigateway" table, select "Items" tab, and the newly inserted item should be displayed.

Dynamo Item

  1. To get all the inserted items from the table, we can use the "list" operation of Lambda using the same API. Pass the following JSON to the API, and it will return all the items from the Dynamo table
{
    "operation": "list",
    "tableName": "lambda-apigateway",
    "payload": {
    }
}

<List Dynamo Items> Similarly, try other operations like read, delete, update etc.

We have successfully created a serverless API using API Gateway, Lambda, and DynamoDB!

Cleanup

Let's clean up the resources we have created for this lab.

Cleaning up DynamoDB

To delete the table, from DynamoDB console, select the table "lambda-apigateway", and click "Delete table"

Delete Dynamo

To delete the Lambda, from the Lambda console, select lambda "LambdaFunctionOverHttps", click "Actions", then click Delete

Delete Lambda

To delete the API we created, in API gateway console, under APIs, select "DynamoDBOperations" API, click "Actions", then "Delete"

Delete API