Creating REST API is very common for web application and mobile apps. Once it is created, suddenly you need to think, on which server you are going to put the code. Then several questions will arise based on application performance, accessibility, cost, flexibility and what not. AWS serverless will help you to reduce your certain questions list and get proper answers about them. 

Serverless works as a Functions-as-a-Service (FaaS) which offers low cost, no server management, a inherently scalable architecture, quick deployment and update.

Let's Begin...

Prerequisite:

• You need to create a NodeJS with Typescript code for REST APIs.
  • I would suggest to checkout Create production ready REST API using nodeJS with TypeScript to proceed further. (Note: I am going to use the same codebase for serverless configuration) 
• Should have an AWS account.
• It would be good to have a custom domain for REST endpoints.
• Should be installed PostgresSQL locally.

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NodeJS with Typescript Code creation

Initially I have started with simple nodejs, then I thought the same to do using Typescript with Nodejs. As I have started my career with Strongly typed language like java & Objective C, So it becomes easy to picked up TypeScript with NodeJs. A complete Production ready REST API creation using NodeJS & Typescript tutorial has been created previously, feel free to check this up. 

Also the boilerplate code based has been uploaded to GitHub. You can find it from here.

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Enable serverless & other necessary npm packages installation

After downloading the application, start with installing npm packages. By using -g flag the serverless package will install globally.

npm install -g serverless

Also install @types/aws-lambda, serverless-offline, serverless-deployment-bucket as well. We'll use AWS Lambda as the compute service. An AWS Lambda function is basically a container. Once the Lambda is invoked, the container spins up and runs the code.

Along with installation, modify the scripts section in package.json file like below - 

"deploy": "npm run build && sls deploy --stage dev",

"start-offline": "npm run build && serverless offline --noTimeout"

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AWS RDS postgres DB creation

Login to your AWS console and navigate to RDS window and select PostgresSQL, Version, Obviously for Free tire. Provide DB instance identifire, master username & password. Under connectivity section, please choose public access as yes, so that you can connect AWS RDS to your locally installed PostgresSQL DB. Also you can import / export your dump DB file to AWS postgresSQL DB as well. 

Once you click on Create Database, it will take about 10 min to create it. So please wait and once it's status Available, navigate to details page and keep few items to be noted in separate file like notepad or text editor. 

Following snapshot might help you to understand better - 

 

Please copy the highlighted Endpoint and open your locally installed PostgresSQL DB. 

 

Once AWS RDS postgresSQL connected successfully, I have created tutorial table and inserting few data into that table too, like below.

If you have any other DB schema (dump) file, that can also be imported into postgresSQL by running the following command.

pg_restore --verbose --clean --no-acl --no-owner -h <<DB endpoint>> -U <<User Name>> -d <<DB name>> latest.dump

Example: 

pg_restore --verbose --clean --no-acl --no-owner -h tutorial.xcderf12345.ap-south-1.rds.amazonaws.com -U master -d tutorial latest.dump

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Configuring YAML file & handler creation for lambda

Once you setup / install PostgresSQL locally on your computer and connected with AWS RDS, its time to create yaml and handler file to your nodejs with Typescript codebase. The serverless framework can help you to get scaffold project, but I would suggest to create the files by yourself, so that you will get a clear idea on it. Create one serverless.yml file in project root folder.

As you have seen, in custom section at the top, I am reading secrects.json file, and I am loading environment variables and pass them to environment section. Let's have a look how the secrets.json file looks like as well.

Next you need to create handler.ts file, and placed the following code over there - 

Once you modified your code and updated with business logic, you can build and run it using severless-offline command.

npm run start-offline

And you could see the node application build successfully and it provides a x-api-key and the endpoint. You need to pass the x-api-key as header to access the just build REST API. 

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Connect nodejs with typescript code with postgres

Once your REST api build & run perfect with local data source, now its time to connect with postgresSQL from nodejs & typescript code. To connect with DB, you need to install few npm packages to make a DB connection and executing queries. If you need details of node with postgres you can check the node-postgres site.

Please install the following two npm packages - 

npm install --save-dev pg

npm install --save-dev @types/pg

The code reference to connect with postgres with nodejs & typescript. 

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Deploy & custom domain addition

Once your APIs are working perfectly with serverless-offline, you can deploy the code to serverless lambda function by using a single command.

npm run deploy

The Serverless framework makes deployments quick and painless. It will take care of bundling up, push all code to S3 bucket and from there it will send to the lambda function. The following screenshot you will get from your terminal.

Please keep the x-api-key and pass it as a header from postman to check the API is working or not. 

For Custom Sub Domain - you can create a sub domain from API Gateway, and add subdomain like tutorial.lazypandatech.com, and saved it. 

Also set API Mapping there as well, like below 

Once you Saved it, it will appear in home page. Now you need to open route53 to create a record. Then select simple route, Define simple record and 

After defining recordset, wait for 10 min to reflect it. For more information about custom domain and deployment, you can check the here as well.

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Test & Error discussion

Now you can open postman, and execute the endpoint and you could see the response. The following error you may encounter during serverless the configuration time or deployment time. 

Error 1: Bucket is not there. 

To solve this error you need to add the serverless-deployment-bucket as a plugin and mentioned it in your serverless.yml. Also you need to add the bucket name. Please check the above section for yml configuration.

npm i serverless-deployment-bucket

Error 2: Invalid API identifier specified 

To solve this error, please check the proper endpoint path and make sure you are passing correct x-api-key as header.

Error 3: 429 Too many requests

I have faced this issue couple of times after deploying the code in Lambda functions. I re-deploy the rest API code and got separate x-api-key. Then after it works fine for me.

Error 3: 502 Bad Gateway Or Internal server error

To solve this error, open AWS RDS and select the DB instance name, navigate to Connectivity & Security. There you could see the VPC security Groups. 

Please click it, and select Inbound option and Edit it.

After allowing anywhere, you could see proper response in postman. 

This is an ever-evolving architecture. With the rise of a serverless relational database, the possibilities are endless in creating entirely serverless infrastructure. I’ve tried my best to explain the process of creating a proper API. 

You could find the complete codebase in GitHub.

Thanks & Happy Coding!

- Lazy Panda