从子进程（NodeJS）调用setTimeout

Question

I would like to call a function through setTimeout using a child process, which may exit before the setTimeout occurs.

1) I assume that if the child process calls the function (even if it's defined externally), the setTimeout will be cancelled if the child process exits. Is this correct?

2) If so, would it be feasible to have the child process signal the parent process to execute the setTimeout instead, or is there a better way to achieve this?

Thanks!

Answer 1

I'm not sure I fully understand, but let me provide some potentially applicable links and examples.

Sending and receiving messages between the master and child process are possible with child.send / process.send which is part of the child_process module and cluster.

For example, clearing a setTimeout when the child process sends a message to the master:

var cp = require('child_process');
var child = cp.fork(__dirname + '/sub.js');

var timer = setTimeout(function(){
  console.log('timed out'); 
}, 5000);

child.on('message', function(msg) {
  console.log(msg);
  clearTimeout(timer);
});

The child

setTimeout(function() {
  console.log('finished doing some long task');
  process.send({ status: 'done' });
}, 3000); // set this to something larger than 5000ms to see the timeout

You might also be interested in the exit and close event for a child process to do something similar.