Micromessaging

This module has been written for Swanest back-end. It eases the use of messaging between services. We use RabbitMQ as the underlying broker service. This library is using amqplib (0.9.1) as a core dependency but we do use some parameters that are only RabbitMQ related so it might not work with other AMQP 0.9.1 brokers.

Supported version of NodeJS 8+

---

Installation

yarn add micromessaging npm install micromessaging --save

API

Full API documentation is at: swanest.github.io/micromessaging

Special thanks to TypeDoc that enabled it.

Dependencies

• RabbitMQ > 3.3.0

Usage

import { Messaging } from 'micromessaging';

// Server
const server = new Messaging('server');
await server.handle('request-name', (message) => {
    // message.body = {how: {are: 'you?'}}
    message.reply({im: 'fine'});
});
await server.connect(); // Connect can be before or after the handlers it doesnt matter.


// Client
const client = new Messaging('client');
await client.connect(); // Connection needs to be established before...
const response = await client.request('server', 'request-name', {how: {are: 'you?'}});
// response = {im: 'fine'}

Notes

v3.0 is a full breaking changes and CANT be used with an other modules using an earlier version.

About what it does:

• RPC model (.request / .handle)
• Event subscription (PUB/SUB) (.emit / .listen)
• Worker queue tasks (.task / .handle)
• Election of a master between services that do have the same serviceName (in new Messaging(serviceName[, serviceOptions]))
• Manage the process quality of service (Qos.ts)
  • The QoS is managed through usage of HeavyEL for event-loop management and the MemoryPressure module to know about memory usage and pressure.
  • What it basically does is to try to keep the process under a certain usage and will stop accepting messages when it reaches a certain threshold to avoid crashes. The reason is that this enables parallelism and it should be properly managed as NodeJS is single threaded.
• Has knowledge about the status of it's peers (through PeerStatus.ts)

TODO

• Manage timeouts in requests.
• getStatus of a service (to know if the service is accepting workload)
• Make API names consistent
• Expose only Messaging so that other modules can do new require('micromessaging').Messaging(...) and new require('micromessaging').Service(...) (to ease backward compatibility but Service should log a warning to tell it's deprecated...)
• Go to the old codebase (within the dir) and check we didn't forgot a working behaviour or features.
• Quadruple check that everything works fine through some good testing!
• Delete old JS codebase
• Add more comments so that typedoc generates a cool and easy doc.
• Travis auto tests
• Publish a doc under GitHub pages => will be under swanest.github.io/micromessaging
• Implement .stop() on the return of emit and handle => see ReturnHandler.