Demo Microservice with NodeJs

A demo microservice that finds distance between two ZIP codes using ZIPCodeAPI api. Source

Creating Microservices with Node.js

Creating a microservice using Node.js which connects to an external API. The requirement for this service is to accept two Zip Codes, preferably US & Canada (due to the nature of the api), and return the distance between them in kms.

Initial Steps

1. Have Node.js installed
2. Run npm init in the root folder for the project. This will create a package.json file that will prompt some questions about the package, if you are not sure how to answer you can use the default.
3. We are going to use two packages, Express and Require that can be installed like this: npm install express request --save

Creating a Server to Accept Requests

Create a file in the root folder for your project called server.js which will be our primary file. This file is creating our server and assigns routes to process all requests.

Defining the routes

The next step is to define the routes for the microservices and then assign each to a target in the controller object (that will control the flow of data in the application). We’ll have two endpoints. One endpoint called “about” that returns information about the application. And a “distance” endpoint that includes two path parameters, both Zip Codes. This endpoint returns the distance, in kms, between these two Zip Codes.

Adding Controller Logic

Within the controller file, we’re going to create a controller object with two properties. Those properties are the functions to handle the requests we defined in the routes module. We have two distinct parts to our controller.

We define a property called about. This property is a function which accepts request and response objects. We’ll only use the response object for this function. Using the name and version information from the package.json file, we’ll build a new object and return it as the response.

For the getDistance functionality, we’ll start by bringing in the distance module. We’ll pass the request and response objects to the find function within this module. This function also includes a callback function. This function accepts an error object (err) and a distance object (dist). If there is an error in the response, we return that with our response; otherwise, we send back the results of the find function.

Making the External Call

This file handles the call to a third-party API. We’ll use the distance API provided by ZIPCodeAPI. You need an API key to use this, and it is free if you register.

Execution

Assuming there aren’t any typos, your application should be ready to execute. Open a console window and run the following command: npm start

Assuming it starts correctly, and the port you define is 3000, you can now open your browser and navigate to: http://localhost:3000/about when you will see the name of the app and the version.

Now if you add two parameters, the two zip codes, you will see something like this: http://localhost:3000/distance/84010/97229

Using microservices to know the distance between two zip codes!