test: add known issue for fs.open() keeping event loop open

[Trott]

Checklist

• make -j4 test (UNIX), or vcbuild test (Windows) passes
• tests and/or benchmarks are included
• commit message follows commit guidelines

[Trott]

This seems ready for review. /ping @ronag

@nodejs/fs: This is a bug, not expected behavior, right? Or is it possibly-expected behavior in certain conditions like NFS-mounted filesystems?

@nodejs/fs and @nodejs/build: Any idea why this keeps the event loop open and times out on Raspberry Pi devices but works fine everywhere else? I'm guessing it has nothing to do with the Pi devices per se but is because those devices are running the tests on NFS-mounted file systems or something like that.

[jasnell]

LGTM for landing the test. No idea on the issue itself but definitely looks like a bug.

[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/32231/

[rvagg]

those devices are running the tests on NFS-mounted file systems

that would be my guess, although speed is another factor that regularly comes in to play - things not happening in the order you expect because everything is slowed down so much so the system gets tripped up. It could be that an unref is getting tripped up in the process and happens too late, or too soon, or something.

If you close the fd in the callback then it exits properly, I'm not sure if that helps at all:

fs.close(fd, function (err) { console.log('closed', err) })

[bnoordhuis]

I'm trying to make sense of this:

1. Callback to fs.open() is called but the test doesn't exit (on the RPi 1's)
2. Call fs.close() from the callback and it exits?

If someone can get me access to one of the affected machines, I'll investigate. Are gdb and strace installed?

[richardlau]

If someone can get me access to one of the affected machines, I'll investigate. Are gdb and strace installed?

@bnoordhuis You're a member of the Build WG so should have access to the secrets repo as documented in https://github.com/nodejs/build/blob/master/doc/ssh.md. The RPI's are behind a jumpbox -- the ansible script described in the ssh doc will write that into your ssh config file for easy access, otherwise the proxy command is templated in https://github.com/nodejs/build/blob/d4b074cd221cce329ee1f31292e3114845390a56/ansible/ansible.cfg#L24 with the hosts defined in https://github.com/nodejs/build/blob/master/ansible/inventory.yml.

test-requireio_williamkapke-debian10-arm64_pi3-1 (from https://ci.nodejs.org/job/node-test-binary-arm-12+/6210/RUN_SUBSET=0,label=pi3-docker/) looks like one of the machines to exhibit the issue. I just checked and that one seems to have gdb and strace installed.

[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/32257/

[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/32258/

[Trott]

Landed in 6ae1b9c

[addaleax]

Fwiw, this test is flaky on v12.x in the sense that apparently, it does succeed there occasionally.