Node.js Design Patterns/

...

/

Using External Processes (II)

Using External Processes (II)

Learn how to prevent the event loop from blocking using external processes.

We'll cover the following...

Let’s now implement the worker (our child process).

Note: It’s good to know that the send() method available on a child process instance can also be used to propagate a socket handle from the main application to a child process (look at the child_process documentation). This is actually the technique used by the cluster module to distribute the load of an HTTP server across multiple processes.

Implementing the worker

Let’s create the workers/subsetSumProcessWorker.js module, our worker process.

import { SubsetSum } from '../subsetSum.js'
process.on('message', msg => {                                          //(1)
  const subsetSum = new SubsetSum(msg.sum, msg.set)
  subsetSum.on('match', data => {                                       //(2)
    process.send({ event: 'match', data: data })
  })
  subsetSum.on('end', data => {
    process.send({ event: 'end', data: data })
  })
  subsetSum.start()
})
process.send('ready')

We can immediately see that we’re reusing the ...