forcing heap snapshot via signal does not allow specifying custom directory

[mateodelnorte]

Version

18

Platform

mac

Subsystem

No response

What steps will reproduce the bug?

1. start node process with node --heapsnapshot-signal=SIGUSR2 --diagnostic-dir=/opt/crashes test.js
2. send signal to snapshot with kill -USR2 [pid]
3. application will attempt to write the heap shapshot to cwd

Why is this important? --diagnostics-dir is currently being used to write files for heap profiling, but not ad-hoc heap dumps. When running in a production environment, the application cwd is often read only. Application developers must be able to specify where heap dumps will be saved.

Note, no parameters are being passed into this function execution: https://github.com/nodejs/node/blob/c24a61b3f6815b9d12b491ac869335feff86a24b/lib/internal/process/pre_execution.js#LL376C17-L376C17. A path should be passed to this function, such that the full filename can be constructed.

How often does it reproduce? Is there a required condition?

No response

What is the expected behavior? Why is that the expected behavior?

Note, no parameters are being passed into this function execution: https://github.com/nodejs/node/blob/c24a61b3f6815b9d12b491ac869335feff86a24b/lib/internal/process/pre_execution.js#LL376C17-L376C17. A path should be passed to this function, such that the full filename can be constructed.

What do you see instead?

writeHeapSnapshot(); attempts to write to the cwd. The code path for writing to a provided path is never utilized.

Additional information

No response

[bnoordhuis]

Pull request welcome. The relevant code is here:

node/lib/internal/process/pre_execution.js

Lines 366 to 387 in 76ae7be

	function initializeHeapSnapshotSignalHandlers() {
	const signal = getOptionValue('--heapsnapshot-signal');
	if (!signal)
	return;
	require('internal/validators').validateSignalName(signal);
	const { writeHeapSnapshot } = require('v8');
	function doWriteHeapSnapshot() {
	writeHeapSnapshot();
	}
	process.on(signal, doWriteHeapSnapshot);
	// The code above would add the listener back during deserialization,
	// if applicable.
	if (isBuildingSnapshot()) {
	addSerializeCallback(() => {
	process.removeListener(signal, doWriteHeapSnapshot);
	});
	}
	}

[MrJithil]

I am on it.

[alexgorunescu97]

I was actually in the process of creating a PR. Can I go ahead with it? I saw that it was labeled as a good first issue and I wanted to make a contribution.

[MrJithil]

Sorry. Next time, you can comment on the issue and take the work. So that, we can avoid the duplicate work.

[WhiteMinds]

It looks like this issue hasn't been responded to in a while, so I created the PR: #49496

[RafaelGSS]

Completed in #47854