nodejs/node

Calling disconnect causes processes spawned by cluster module to exit too early

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#27,679 opened on May 13, 2019

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clusterhelp wanted

Description

  • Version: 12.2.0 but could also reproduce on 10.15.3
  • Platform: Darwin 18.5.0 Darwin Kernel Version 18.5.0: Mon Mar 11 20:40:32 PDT 2019; root:xnu-4903.251.3~3/RELEASE_X86_64 x86_64
  • Subsystem:

Consider the following script:

const cluster = require('cluster');
const childProcess = require('child_process');

const useCluster = false;
const isMaster = useCluster ? cluster.isMaster : !process.argv.includes('worker');

if (isMaster) {
  if (useCluster) {
    cluster.fork(__filename);
  } else {
    childProcess.fork(__filename, ['worker']);
  }
} else {
  setTimeout(() => console.log('hi from worker'), 1000);
  process.disconnect();
}

When useCluster is true node exits immediately and nothing is printed to the console. When useCluster is false you see "hi from worker" logged after 1s and then node will exit which is the expected behavior. The documentation makes it sound like calling process.disconnect should only close the IPC channel between the master and worker process and should not cause either to exit early if there is still work to do.

Contributor guide

Tech stack
nodejsjavascript
Domain
backend
Issue type
bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
half day
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
stale
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
clear
Prerequisites
Node.js cluster moduleprocess.disconnect APINode.js internals
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
40
Research direction
Investigate the timing of process.disconnect in cluster workers. Look at the cluster module files (lib/internal/cluster/) and how the worker internally listens to the disconnect event. The issue suggests that when cluster.fork is used, the worker disconnects too early, while child process.fork works correctly. Compare the behavior in both cases to identify the root cause. Check the disconnect handling in the cluster worker code.