API-Gateway-project (Arbitor)

A homebrew api gateway for microservice management

This project is an attempt at understanding the programming paradigms behind an API Gateway and to design a homebrew version capable of fulfilling those paradigms.

An API gateway acts as an intermediary between clients and a collection of backend services. Arbitor acts as the Single Point Of Access (SPOA) between itself and the backend service as well as a loadbalancer among mutiple instances of services.

Usage Reference

Add an service

Add the register-service directory in your service. In the regiser-service, edit the .config.js according to your service. The guidelines are as follows:

export const gatewayUrl = "http://localhost:5000/register"

• gatewayUrl : replace with the base_url of the gateway host _base-url_/register.

export const apiData = {
    "api_name" : "proto_login",
    "base_url" : "http://localhost",
    "port"     : "3000",
}

Parameter	Type	Description
api_name	string	Required. Service_name identifier of the service
base_url	string	Required. Base_url for the service hosting.
port	string	Required. Port number for the service.

export const routes = {
    {
        "api_key"     : "/health",
        "endpoint"    : "/health",
        "access_type" : "public",
    },
    {
        "api_key"     : "/login",
        "endpoint"    : "/login/user",
        "access_type" : "public",
    },
}

Parameter	Type	Description
api_key	string	Required. Key your endpoint to be acknowledged as
endpoint	string	Required. Endpoint in your service.
access_type	string	Required. private or public endpoint

[Note!]

The /health route is required for the gateway to be able to remove the service from service registry when the service goes down. Removing it or not providing it in the service may cause issues.

In the service main file, create a registrar instance. Example code here uses the express framework to run server.

import express from 'express';
import registrar from './register-service/registrar.js';

const app = express();
const registrar = registrar(); //Initiate an instance

app.listen(3000, () => {
  console.log(`Starting the app..`);
  regsitrar.registerToGateway(); //Registering to the gatewya on start.
})

Upon running the service with the API gateway running, the service wiill register itself to the gateway.

Calling a registered service

ALL /:service_name/:service_key

Parameter	Description
service_name	The name under which the service is registered
service_key	The key for URI in the Service, register to the gateway

Naming limitations

The gateway, so far cannot parse parameters in the URL path, it is suggested to pass any parameters as query strings as those are fed forward. Later versions of the application will look to solve this issue.

Deleting a registered service

The gateway is capable of performing health checks for each of the services registered to it and will periodically remove the service. If a service goes down, it will be unregistered by the health-checker. Upon restarting the service, it is expected that the service re-registers itself.

Migrations

This project uses node-pg-migrate for database migrations. The following commands are available to be run inside the /arbitor dir :

• npm run migrate create: Creates a new migration file.
• npm run migrate up: Applies pending migrations to the database.
• npm run migrate down: Reverts the latest migration applied to the database.

[Note!]

You will need to set the DATABASE environment variable before running any migration commands.

Technologies

• JavaScript + DocStrings for type definitions.
• Express.js: A popular Node.js web framework for building web applications and APIs.
• node-pg: A Node.js library for interacting with PostgreSQL databases.
• node-pg-migrate: A library for managing database migrations with PostgreSQL.

Installation

Steps for local usage

1. Clone this repository:

git clone https://github.com/KausTarafdar/arbitor.git

2. Install dependencies:

Inside the /arbitor run :

npm install

3. Usage:

• Create a .env file in the /arbitor dir and add the following :-

##Server Info
PORT=
URL=

##Database Info
DB_USER=
DB_PASSWORD=
DB_HOST=
DB_PORT=
DB_NAME=

• To start in production mode run :-

npm run start-dev

Starts the server using nodemon allowing the server to run constantly tracking file changes.

• To start in deployment run :-

npm start