Node: fsPromises.truncate doesn't close fd.

[sheepa]

• Version: v12.18.1
• Platform: Linux 5.4.0-37-generic #41-Ubuntu SMP x86_64 x86_64 x86_64 GNU/Linux
• Subsystem:

What steps will reproduce the bug?

fsPromises.truncate(path) will result in a warning a few seconds later: (node:1387179) Warning: Closing file descriptor 22 on garbage collection - Using the callback truncate await new Promise((res, rej) => { fs.truncate(file, (err, ret) => { if(err) rej(err); else res(ret) }) }) works fine without such warning.

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

Every time.

What is the expected behavior?

Not having this warning.

What do you see instead?

Additional information

[Himself65]

Could you show the code to reproduce?

[bnoordhuis]

I'm not able to reproduce. As an example:

$ node --expose_gc
> fs.promises.truncate('/tmp/x.txt').then(_ => gc())  // x.txt exists
Promise { <pending> }
> 

No warnings.

@sheepa I'm going to close this but I can reopen if you post steps to reproduce.

[sheepa]

const fs = require('fs').promises

async function test()
{
  const file = '/tmp/x.txt'
  await fs.writeFile(file, 'data')
  await fs.truncate(file)
  gc()
}

test()

The following code give me (node:268029) Warning: Closing file descriptor 19 on garbage collection

[jasnell]

@bnoordhuis... closing this was premature.

This is an issue that was fixed in master in eadc385 but it does not look like the fix was backported to 12.x yet. See... https://github.com/nodejs/node/blob/v12.x/lib/internal/fs/promises.js#L307-L309

C:\Users\jasne\Projects\tmp>node --expose-gc
Welcome to Node.js v12.18.0.
Type ".help" for more information.
> fs.promises.truncate('t.js').then(_ => gc())
Promise { <pending> }
> (node:23652) Warning: Closing file descriptor 4 on garbage collection

[jasnell]

@sheepa ... I'll be opening a PR to backport the fix to 12.x soon but it will take a while for that to land in a release. You can work around the issue for now by using the ftruncate() method instead using the exact same pattern used in the fix:

async function myTruncate(path, len) {
  const fd = await open(path, 'r+');
  return ftruncate(fd, len).finally(fd.close.bind(fd));
}

[richardlau]

This is an issue that was fixed in master in eadc385 but it does not look like the fix was backported to 12.x yet. See... https://github.com/nodejs/node/blob/v12.x/lib/internal/fs/promises.js#L307-L309

eadc385 references https://github.com/nodejs/node/pull/28858 as the PR and that's marked semver-major so it will be ignored by our tooling (e.g. branch-diff) and processes when evaluating what could be backported.

[jasnell]

@richardlau ... yeah, I spotted that. This one commit is not semver-major. I'm working on a backport PR now for 12.x but github is giving me the Unicorn of Sadness at the moment. Will open as soon as the site becomes responsive again

[jasnell]

PR opened!