yello

Communication primitives for microservices on top of AMQP.

This module handles the main communication challenges our apps face in our microservice architecture. Both request/response type and publish/subscribe. It handles topic based subscription as well.

API

Create a new client.

var yello = require('yello');
var client = yello('amqp://user:password@amqphost');

request/response

Just keep in mind, by default these handlers will only handle 1 request concurrently. Use maxConcurrency option to increase that limit.

API providers can set up endpoints:

client.respond('sayHello', request => {
  // response can either be a value or a promise
  return Promise.resolve({
    message: `Hello ${request.name}!`
  });
});

To which clients can request:

client.request('sayHello', { name: 'Yello' })
  .then(response => {
    console.log(response.message);
    // "Hello Yello!"
  })

publish/subscribe

Just keep in mind, by default these handlers will only handle 1 request concurrently. Use maxConcurrency option to increase that limit.

Distributed worker

Multiple registrations under the same worker Id. Only one will receive the event. Useful for distributed workers.

// instance 1
client.subscribe('emailSvc', 'emails.pwRecovery', job => {
  return sendEmail(job.email);
});

// instance 2
client.subscribe('emailSvc', 'emails.pwRecovery', job => {
  return sendEmail(job.email);
});

Only one of these will receive the event when we publish it:

client.publish('emails.pwRecovery', { email: 'yello@example.com' });

Catch all events

Multiple registrations, Each one will receive the event.

// instance 1
client.subscribe(null, 'config.refresh', () => {
  return config.refresh();
});

// instance 2
client.subscribe(null, 'config.refresh', () => {
  return config.refresh();
});

Both will receive the event when we publish it:

client.publish('config.refresh');

Topic based subscription

client.subscribe('emailLogger', 'emails.*', job => {
  return console.log(`Received email job for ${job.email}`);
});