Integrating AWS API Gateway, Lambda and DynamoDB

In the current world of API, every mobile application and website have to communicate using dedicated API servers. These dedicated servers are explicitly set to handle the API calls for an application. API servers act as an intermediary between the application and the database. The bottleneck of this setup is that the API server has to be maintained to handle all the API calls. The increase in the number of API calls, increases the load of the API server which may require auto-scaling, which is cost-consuming.

The latest approach of the best architects is to utilize a new AWS service that explicitly replaces the need for a dedicated API Server. AWS API Gateway provides the ability to act as an interface between application and database which uses AWS Lambda function as the backend.

To get the essence of AWS API Gateway, we need to get hands-on with it. The next part of the blog is a detailed tutorial on how to use AWS API Gateway along with AWS Lambda & DynamoDB.

People who are familiar with DynamoDB, API Gateway and Lambda can proceed with the high-level instructions. Also for people who are new to these services, there are detailed instructions which can be followed for step-by-step guidance.

The first step will be to create a DynamoDB table which stores the data. Next a Lambda function which inserts the data into DynamoDB table. An API Gateway is setup to trigger the Lambda function. Finally a REST Client will be used to call the API.

Step 1: Create a DynamoDB table:

Create a DynamoDB table named Employee with the attributes of primary key as emp_id. Accept the rest of attributes as default and review the table details.

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1. Go to console.aws.amazon.com and sign into your account. On the services dashboard select DynamoDB. Click on Create Table.
2. On the next screen
   • Enter Employee as the Table Name.
   • Select Primary Key Type as Hash.
   • Provide the Hash attribute Name (like an Primary key) as emp_Id then click Continue.
3. Skip the Global indexes settings on the next screen.
4. On the Provision Throughput Capacity screen, leave the read and write capacity as 1 then click Continue.
5. Finally review the settings and click Create table.

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Step 2: Create a Lambda Function:

Create a node.js Lambda function called addEmployee. Use code from the following location, https://s3-ap-southeast-1.amazonaws.com/cloudthatcode/addEmployee.zip. Replace IAM access and secret keys of a user with access to write into the DynamoDB table.

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1. On the Lambda service page click on Get Started Now.
2. On the next screen, click Skip.
3. On the next screen
   • Enter the name of the function as  addEmployee.
   • Enter a description for the function.
   • From the dropdown select the runtime as Node.js.
4. Scroll down to the bottom of the screen and do the following
   • Select code entry type as Edit Code Inline.
   • Download the sample code by visiting this URL  https://s3-ap-southeast-1.amazonaws.com/cloudthatcode/addEmployee.zip.
   • Paste the sample code provided into the editor as shown below.
   • Create a user in IAM with access to write into the DynamoDB table.
   • Replace IAM access and secret keys of that user into the code and save.
5. Next scroll down further and on the following
   • Leave the handler as default.
   • For IAM Role, select Create New IAM Role, select DynamoDb event stream Role, which will redirect you to the IAM Management Console.
   • Enter the name as dynamodb-Access and click Allow.
6. Under Advanced settings leave everything as default and click Continue.
7. Finally review the function click Create function.
8. Now we will test the function.
   • Click on Test .
   • Provide the parameters for the Lambda Function as given below and submit.
9.  The Execution result  will show as succeeded and the record will be inserted in the Employee table.

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Step 3: Create an API in API Gateway :

Next create an API called Employee_API, a resource called employee and create a POST Method. Use Lambda as the integration type and select the Lambda function you created earlier.

Test the API with the following values from the console.

You should see the entries in the DynamoDB table.

For creating an API we need to create Resource, create POST method under the resource and utilize the Lambda function as integration type and the Deployment of API is up for launch.

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For creating API we will Create Resource, create POST method under the resource and we will provide the Lambda function as integration type and then we will Deploy the API.

1. Go to the API Gateway service page and click on Get Started.
2. Enter the API name as Employee_API.
3. Provide a Description and Create API.
4. On the top right of the screen click on Create Resource.
5. Provide the Resource Name as employee and click Create Resource.
6. Click on Create Method.
7. Select POST Method .
8. Next do the following
   • Select Lambda Function as the Integration type.
   • Select the Lambda Region and the Lambda Function you created earlier.
   • Click Save.
9. Grant the Permission changes for the API lambda function by clicking OK
10. The API has been created.
11. Next Test the API.
12. Click on TEST in the console as shown below.
13. Provide payload as given and click Test.
14. You should will get a success response and check if the record has been inserted into the table.
15. We will now Deploy the API.
16. Click on the Deploy API.
17. Next do the following
    • Select New Stage.
    • Provide Stage Name and Description and click Deploy
18. Once the Stage has been deployed and you will get the invoke URL.

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Step 4: Call the API using REST Client

Test the API setup. For this Install a REST client. There are extensions for Mozilla firefox and Chrome which can be used which can be use to make REST calls. Install the one specific to your Browser. Invoke the API URL with the following values

Check the DynamoDB table again for the entries.

The response from the DynamoDB is processed by the Lambda function and routed via the API Gateway.

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1. Install the REST client for Mozilla/Chrome. Go to Add-ons/extensions and search for RESTClient and Install.
2. Select the http POST Method
3. Enter the Invoke URL as the URL. Add your Resource Name i.e. employee to the end of the URL.
4. Enter the Payload as provided.
5. Send the Request.
6. You should see the a Successful response and the final employee entry added to the Employee table.

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With minimal effort a REST API has been created which accepts data,  which in turn gets processed by Lambda function and finally stored in a DynamoDB table. This API is ready for use and can be used in any application.

The API gateway frees the developer from maintaining infrastructure for APIs. On the whole AWS API Gateway is a beneficial package for the developer. The API gateway provides nifty features where we can create different stages for development. It also has a useful testing platform which can be used to test the calls. It also provides caching and monitoring.

In my next blog I have talked about securing your API’s in API gateway, passing Query string & headers, transforming response type and returning the custom error code.The hands on is included. If you have any queries on API gateway or you have trouble getting it setup, feel free to drop a question into the comment section below or you can also ask the questions to https://forum.cloudthat.com

Thank you.

WRITTEN BY CloudThat

CloudThat is a leading provider of cloud training and consulting services, empowering individuals and organizations to leverage the full potential of cloud computing. With a commitment to delivering cutting-edge expertise, CloudThat equips professionals with the skills needed to thrive in the digital era.