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Hanging when using MessagePort from ES customization hooks via --import #52846
Description
Activity
This is not hanging but still running IMO. It must be happening becauseport1.onregisters an event handler that keeps the process alive. You could implement on your protocol layer some message that unsubscribes for the 'message' event and that will allow the process to end.
for example modify your message handler to get one message and unsubscribe like this:port1.on('message', (msg) => { console.log(`msg = ${msg}`); port1.off('message'); });the.offcall can be based on any other application logic on your apps side.@nodejs/loaders please correct me if I'm wrong.
EDIT: tried that now, seems wrong. but you could
unrefthe ports used for the comunication from the customization hooks thread:port1.on('message', (msg) => { console.log(`msg = ${msg}`); }); port1.unref(); port2.unref();Thank you @dygabo!
unref()ingport1seems to be sufficient for my initial example - is there a reason to callport2.unref()as well?I am happy to add a PR to update the example in the node docs (https://nodejs.org/api/module.html#initialize) so others don't encounter this.
Reacted by Benjamin Gruenbaumyes, it should be enough to
unrefport1to allow the process to stop.- added a commit that references this issue
on Jul 1, 2024 - added 2 commits that reference this issue
on Jul 12, 2024
Version
v21.1.0
Platform
Microsoft Windows NT 10.0.22631.0 x64
Subsystem
No response
What steps will reproduce the bug?
Running
node --import ./bootstrap.mjs ./index.mjswill hang with the following code.How often does it reproduce? Is there a required condition?
Reproducible 100% of the time.
What is the expected behavior? Why is that the expected behavior?
For
nodeto printand return normally.
What do you see instead?
nodehangs, but prints the expected to the consoleAdditional information
nodereturns normally and no longer hangs ifport.close()is added afterport.postMessage('initialize');,port1.on('message', ...)This code was taken and simplified from the example in the documentation here https://nodejs.org/api/module.html#initialize.