Cluster: worker.disconnect waits for handles to close before firing "disconnect" event

[cjthompson]

In the classic (0.10) cluster scheduler (SCHED_NONE), when worker.disconnect() is called, the worker immediately emits a "disconnect" event, then proceeds to wait for exiting connections to close before terminating the child process:

node/lib/cluster.js

Line 404 in f299d87

Worker.prototype.disconnect = function() {

In the Round Robin mode, worker.disconnect() does not fire a disconnect event, and it waits for all the handles to close before disconnecting the child process.

node/lib/cluster.js

Line 655 in f299d87

Worker.prototype.disconnect = function() {

In short, the old behavior was to: 1) fire "disconnect", 2) wait for handles to close, 3) fire "exit". The new behavior is 1) disconnect IPC (but don't fire "disconnect" event), 2) wait for handles to close, 3) fire "disconnect" event, 4) fire "exit" event

The scenario I'm looking at is if a worker disconnects, I'd like the master to immediately start a new worker in its place, while waiting for the previous worker to terminate (or force terminate it if it takes too long to close on its own).

This was possible with the old scheduler, but not the round robin scheduler.

[cjthompson]

I've also been able to trigger this error after a worker disconnects:

events.js:141
      throw er; // Unhandled 'error' event
      ^

Error: IPC channel is already disconnected
    at process.target.disconnect (internal/child_process.js:631:26)
    at Server.checkRemainingHandles (cluster.js:659:17)
    at Server.g (events.js:260:16)
    at emitNone (events.js:67:13)
    at Server.emit (events.js:166:7)
    at emitCloseNT (net.js:1521:8)
    at doNTCallback1 (node.js:430:9)
    at process._tickCallback (node.js:352:17)

[cjihrig]

What version of Node are you using? What operating system? You're a lot more likely to get help if you provide code (with no external dependencies) to reproduce the problem.

[Trott]

Note also that there have been two possibly-relevant changes to disconnect behavior since the version of cluster.js linked to in this issue.

• f9f1dd9
• 9571be1

[cjthompson]

I've been unable to reproduce the issue using a simple example, so I'm closing this issue.