thomasio101 / mini-microservices

A small and simple NodeJS library for creating microservice based applications.

mini-microservices

A small and simple NodeJS library for creating microservice based applications.

Contents

• Quickstart

Advanced features

• Procedures

Quickstart

To get started with mini-microservices, create a new folder in which your project will reside.

Once you've made this folder, it's time to install mini-microservices, for this you'll need to download the newest release from the releases page. When the download has finished, extract the contents of the downloaded archive into your project folder, the file structure should look like this:

<Your project folder>
|-LICENSE
|-index.js
|-package.json
|-procedures.js
|-services.json

Now you can start writing your own services, in this case we'll make a simple express application which will send a greeting based on the provided name.

Firstly, create a new file called greetingService.js this service will take a name and return a personalised greeting.

Write the following in this file:

module.exports = (serviceRegistry) => {
    return (name) => `Hello ${name}.`
}

Let's take a closer look at this code to understand how mini-microservices work:

• We always export a function that takes the serviceRegistry as an argument, this is the basic structure of any mini-microservice. (We'll get back to using the serviceRegistry when we create the next service.)
• Whatever you return from the module you export will be what other services will have access to, this can be anything, in our case it's a function.

Now you'll need to create the express service, for this, create a new folder called expressService. Now open a command line in this folder and run the following command (Just hit enter for all prompts):

npm init

Then install Express by running the following command:

npm i express

Now create a file in the expressService folder called index.js, open this file and enter the following code:

const express = require('express')

module.exports = (serviceRegistry) => {
    const app = express()

    app.get('/greeting', function(req, res) {
        res.send(
            serviceRegistry.greetingService(req.query.name)
        )
    })

    app.listen(80)

    return app
}

Now open services.json and replace it with the following JSON:

{
    "expressService": {
        "path": "./expressService/index.js",
        "dependencies": [
            "greetingService"
        ]
    },
    "greetingService": {
        "path": "./greetingService.js"
    }
}

Now run index.js and open your web browser, go to http://localhost/greeting?name=<INSERT YOUR OWN NAME> and you'll see a greeting!

Now you have a basic understanding of mini-microservices, go ahead and make something amazing!

Procedures

Unmodified, the procedures.js file contains the following code:

module.exports = (serviceRegistry) => {

}

This function is executed after all services have been loaded, an example of a situation where this can be useful is when you need to start an http server after the starting process is complete.