child_process.spawn leaves spawned process hanging

[dignifiedquire]

• Version: 6.3.0
• Platform: Darwin dignified-station-3.local 15.6.0 Darwin Kernel Version 15.6.0: Thu Jun 23 18:25:34 PDT 2016; root:xnu-3248.60.10~1/RELEASE_X86_64 x86_64
• Subsystem: child_process

Given the following code

'use strict'

const spawn = require('child_process').spawn

const cmd = 'tail'
const args = ['-f', '/dev/null'/*, '&'*/]
const p = spawn(cmd, args)

console.log('starting')
setTimeout(() => {
  console.log('exiting')
  process.exit()
}, 2 * 1000)

I would expect the spawned process to be terminated when the execution of it terminates, but this does not seem the case. Checking after this code is executed I find

$ ps auxw |grep tail
dignifiedquire  21100   0.0  0.0  2434832    664 s004  S     9:44PM   0:00.00 tail -f /dev/null &

[cjihrig]

Can you try removing the '&' arg?

[dignifiedquire]

Can you try removing the '&' arg?

Yes, same behaviour, updated the script above.

[dignifiedquire]

I should probably note that this is not specific to tail -f, it was just the most minimal example I could find to reproduce this without introducing external binaries.

[bnoordhuis]

I would expect the spawned process to be terminated when the execution of it terminates

'it' refers to the node process, not the child process? That's the expected behavior, it's how UNIX generally works.

EDIT: To be clear, it's expected that the child stays alive when the parent terminates.

[dignifiedquire]

'it' refers to the node process, not the child process?

Yes.

That's the expected behavior, it's how UNIX generally works.

Thanks for the clarification. While I understand that UNIX works this way, I feel it would be very beneficial for API to expose a way of saying kill this process whenever I die to ensure this cleanup happens.
To do this in userland as far as what I have found currently is that I need to listen to multiple events on process, .i.e. exit and uncaughtException and SIGINT to ensure that this cleanup happens, which seems to be prone to errors.

[addaleax]

@dignifiedquire Does using https://www.npmjs.com/package/signal-exit present a solution for that problem to you?

[dignifiedquire]

@addaleax thank you 😊 I did not know about that module, this certainly helps with ensuring on listening to the right signal.

Thank you everyone for the super quick turn around and help!