CODEWITHSUNDEEP
javascriptnode.js
weagle08
weagle08

Reputation: 1964

NodeJS exiting prematurely

I have a NodeJS child process listening for messages with process.on('message', callback) however the process is exiting immediately. From my reading this is not supposed to happen since I have a callback waiting on the event loop so why is NodeJS exiting?

The example code below should be able to run as a standalone NodeJS process and not exit, correct?

Node Version: 7.3.0

example code:

function handle(msg) {
    //do work here
}

process.on('message', (msg) => {
    handle(msg);
}

Upvotes: 2

Views: 1246

Answers (1)

GPX
GPX

Reputation: 3645

Here's a sample program that emulates your problem.

master.js

const cp = require('child_process');
const child = cp.spawn('node', ['./child.js'], {stdio: ['ipc']})
child.stdout.on('data', data => console.log(data.toString()))
child.send('immediate execute MESSAGE 1')
setTimeout(() => {
    child.send('late execute MESSAGE 2 after 4 seconds')
}, 4000)

child.js

function handle(msg) {
    console.log('Handling message -> ', msg);
}

process.on('message', (msg) => {
    handle(msg);
});

process.on('exit', () => {
    process.disconnect();
});

The key things to note here are -

  1. child_process.spawn - spawn returns a Buffer, and you can start listening to the stdout stream as soon as the child process starts.
  2. {stdio: ['ipc']} - this option lets you open an IPC channel with the spawned child process. When you want to disconnect the child, simply use child.disconnect().

Upvotes: 1

Related Questions