Satellite

Overview

Satellite is a Microservice Framework utilized by the Telescope project that helps creates an Express server, with many components preconfigured. Furthermore, Satellite has built-in support for node modules such as cors and Helmet, with default settings, eliminating the need for manual installation and configuration.

Microservices is an approach to developing software in such a manner that it is composed of small independent services that communicate with an API. Telescope is an example of software using microservices. The projects we work on in other WEB courses utilize monolithic architectures, as all the processes are tightly coupled and run as a single service. Microservices architecture is easy to scale, deploy, and update.

Installation and Configuration

Satellite can be installed as a dependency in a Nodejs project using the following npm command:

npm install --save @senecacdot/satellite

To use Satellite, the following JWT verification-specific environment variables need to be configured:

Variable	Description
`JWT_SECRET`	the secret used for JWT token verification
`JWT_AUDIENCE`	the audience (aud) claim expected in JWT token verification
`JWT_ISSUER`	the issuer (iss) claim expected in JWT token verification

Basic Usage

// index.js

// import the Satellite constructor and preconfigured logger
const { Satellite, logger } = require('@senecacdot/satellite');

// defining the microservice
const service = new Satellite();

const HTTP_PORT = process.env.PORT || 8000;

// adding a route
service.router.get('/', (req, res) => {
    res.json({ message: 'Hello from Home route'});
});

// run service on the specified port:
service.start(HTTP_PORT, () => {
    logger.info(`Satellite microservice running on port: ${HTTP_PORT}`);
});

Output

Express vs. Satellite

Express is a Nodejs framework used to develop the backend of a web application. Being a Nodejs framework means Express is a customized version of Nodejs with preconfigured components to speed up development. On the other hand, Satellite is a microservice framework, running Express under the hood to create a server with many settings enabled, requiring minimal configuration from the developers.

Key Features

Satellite offers built-in support for cors and helmet, turned on by default
Optional hooks such as beforeParsers and beforeRouter that grant access to the app object during creation but prior to adding the hooks
Ability to specify optional router in stead of default one created automatically by Satellite
Ability to specify an optional credentials object with key and cert values without having to require https
middleware functions such as isAuthenticated and isAuthorized to help with routes
logger based on Pino to output log messages with context
hash function, which returns a 10-character-long hash for the value provided
createServiceToken function that generates a short-lived access token with the "service" role
createError function that generates unique HTTP Error object using the http-errors library
Ability to create instance an of ElasticSearch using the Elastic() constructor
fetch function which accepts url and options as arguments to initiate an HTTP request to an endpoint, using node-fetch.