nest-cluster-hub

A Nest module for communication between master and worker processes based on node-cluster-hub

Installation

To begin using it, we first install the required dependency.

$ npm install --save nest-cluster-hub

Getting started

Once the installation is complete, import the ClusterHubModule into the root AppModule and run the forRoot() static method as shown below:

import { Module } from '@nestjs/common';
import { ClusterHubModule } from 'nest-cluster-hub';

@Module({
  imports: [
    ClusterHubModule.forRoot(),
  ],
})
export class AppModule {}

Next, inject the ClusterHub instance using the @InjectClusterHub() decorator.

constructor(@InjectClusterHub() private readonly hub: ClusterHub) {}

Sending messages

Sending a message to a specific worker

if (cluster.isPrimary) {
  this.hub.sendToWorker(worker, 'master-to-worker', 1);
}

You can just pass any string instead of cluster.Worker. The library uses HashRing to let you find the correct worker for the key which is closest to the point after what the given key hashes to.

Sending a message to a random worker

if (cluster.isPrimary) {
  this.hub.sendToRandomWorker('master-to-worker', 1);
}

Sending (broadcasting) a message to all workers

if (cluster.isPrimary) {
  this.hub.sendToWorkers('master-to-worker', 1);
}

Sending a message to the master (primary)

if (cluster.isPrimary) {
  this.hub.sendToMaster('master-to-master', 1);
}

if (cluster.isWorker) {
  this.hub.sendToMaster('worker-to-worker', 1);
}

Handling received messages

if (cluster.isPrimary) {
  this.hub.on('master-to-master', (data) => {
    console.log('master-to-master received');
  });

  this.hub.on('worker-to-master', (data) => {
    console.log('worker-to-master received');
  });
}

if (cluster.isWorker) {
  this.hub.on('master-to-worker', (data) => {
    console.log('master-to-worker received');
  });
}

Handling received messages with @OnMessage() decorator

@OnMessage('master-to-worker')
async handleMessage(data) {
  console.log('master-to-worker received');
}

Request-response

Sending a request to a specific worker

if (cluster.isPrimary) {
  this.hub.requestWorker(worker, 'mult', { a: 5, b: 7 }, (err, sum) => {
    console.log('Mult in master: ' + sum);
  });
}

You can also pass any string instead of cluster.Worker to find the correct worker.

Sending a request to a random worker

if (cluster.isPrimary) {
  this.hub.requestRandomWorker('mult', { a: 5, b: 7 }, (err, sum) => {
    console.log('Mult in master: ' + sum);
  });
}

Sending a request to the master (primary)

if (cluster.isPrimary) {
  this.hub.requestMaster('sum', { a: 5, b: 7 }, (err, sum) => {
    console.log('Sum in master: ' + sum);
  });
}

if (cluster.isWorker) {
  this.hub.requestMaster('sum', { a: 5, b: 7 }, (err, sum) => {
    console.log('Sum in worker: ' + sum);
  });
}

Handling requests and responses

if (cluster.isPrimary) {
  this.hub.on('sum', (data, sender, callback) => {
    callback(null, data.a + data.b);
  });
}

if (cluster.isWorker) {
  this.hub.on('mult', (data, sender, callback) => {
    callback(null, data.a * data.b);
  });
}

Handling requests and responses with @OnRequest() decorator

@OnRequest('mult')
async handleMessage(data, sender, callback) {
  callback(null, data.a * data.b);
}

Sharing data between processes

this.hub.set('foo', 'bar', () => {
  this.hub.get('foo', (err, value) => {
    console.log(value === 'bar'); // true
  });
});

Retrieving existing workers

Finding a worker

if (cluster.isPrimary) {
  this.hub.getWorker('foo');
}

Retrieving all workers

if (cluster.isPrimary) {
  this.hub.getWorkers();
}

Example

A working example is available here.

License

MIT