fs: support abortsignal in writeFile #35993

benjamingr · 2020-11-06T11:48:51Z

Now that #35911 is landed the next suggestion in #35877 by @mcollina was fs.writeFile (here #35877 (comment) ) - so I am going over the suggestions one by one and adding AbortSignal support.

This PR lets you abort an ongoing writeFile request.

const controller = new AbortController();
const { signal } = controller;
const data = new Uint8Array(Buffer.from('Hello Node.js'));
(async () => {
  try {
    await fs.writeFile('message.txt', data, { signal });
  } catch (err) {
  // When a request is aborted - err is an AbortError
  }
})();
// When the request should be aborted
controller.abort();

Note that unlike readFile this is very stateful - so some of the data will be written to the file (this is expected IMO). I vaguely recall in the summit @addaleax has something smart to say regarding the error but I don't remember the conclusion. I am happy to tack the offset (how many bytes were written) on the AbortError if that would help.

aduh95 · 2020-11-06T11:52:20Z

lib/internal/fs/promises.js


  const fd = await open(path, flag, options.mode);
-  return writeFileHandle(fd, data).finally(fd.close);
+  if (options.signal && options.signal.aborted) {


Suggested change

if (options.signal && options.signal.aborted) {

if (options.signal?.aborted) {

Bacause no backporting and 12.x?

AbortController is not available on v12, is it?

lib/internal/fs/promises.js

benjamingr · 2020-11-06T11:54:47Z

@nodejs/documentation anyone can help me with the "SyntaxError: Unexpected token (1421:13)" acorn error I'm seeing?

aduh95 · 2020-11-06T12:10:23Z

@nodejs/documentation anyone can help me with the "SyntaxError: Unexpected token (1421:13)" acorn error I'm seeing?

It's related to optional chaining. Fixed by #35994.

benjamingr · 2020-11-06T12:20:51Z

@aduh95

It's related to optional chaining. Fixed by #35994.

That makes sense sort of but... I did not use optional chaining in the docs so why is that failing?

aduh95 · 2020-11-06T13:18:23Z

That makes sense sort of but... I did not use optional chaining in the docs so why is that failing?

Not sure either, acorn parsing was added back in #22405.

richardlau · 2020-11-06T20:09:52Z

The docs build parses the JavaScript source to generate apilinks.json, e.g. https://nodejs.org/docs/v15.1.0/apilinks.json. This file maps methods to the line numbers in the source file and I believe it's used by some IDEs.

doc/api/fs.md

jasnell · 2020-11-06T20:28:03Z

doc/api/fs.md

+const { signal } = controller;
+const data = new Uint8Array(Buffer.from('Hello Node.js'));
+fs.writeFile('message.txt', data, { signal }, (err) => {
+  // When a request is aborted - the callback is called with an AbortError


This may be a bit difficult, and is likely something that we should tackle later in a separate PR, but it would be helpful if this reported the number of bytes known to have been written at the point of failure/cancelation.

Yeah, I asked in the description it's actually pretty easy to do - but I remember there were really good arguments regarding whether or not we should do this (in the summit, by @addaleax IIRC) and I don't remember what the conclusion was.

Adding the number of bytes written is actually technically pretty easy here if we just want to approximate how much was written since the last write since we don't actually abort writes in progress only writeAll

Right – I think we basically agreed to see cancellation is a way of expressing disinterest in the result of an operation. Not reporting the number of written bytes goes in line with that. More importantly, if we add cancellation support to the actual fs operations underneath – as we should – then these numbers become inherently unreliable. I would not be in favour of adding this, if somebody wants it, then they should use fs.write() directly without cancelling.

jasnell · 2020-11-06T20:28:41Z

doc/api/fs.md

+```
+
+Aborting an ongoing request does not abort individual operating
+system requests but rather the internal buffering `fs.writeFile` performs.


Users who are unfamiliar with how writeFile works under the covers may find this sentence confusing.

How do you propose we deal with this? Add an extra note to writeFile explaining how it works and suggesting a createWriteStream for performacne sensitive stuff like we do with readFile?

I think it's better to explain how this works underneath instead, and then include the above sentence.

@mcollina @jasnell done PTAL

nodejs-github-bot · 2020-11-07T16:35:11Z

CI: https://ci.nodejs.org/job/node-test-pull-request/34175/

nodejs#35993 (comment)

#35993 (comment) PR-URL: #35995 Reviewed-By: Antoine du Hamel <duhamelantoine1995@gmail.com> Reviewed-By: Rich Trott <rtrott@gmail.com>

benjamingr · 2020-11-10T07:43:43Z

This needs a rebase and some reviews ^^

@jasnell @mcollina any chance this could get a look? It's weird we support it in readFile but not writeFile

aduh95 · 2020-11-10T08:47:34Z

lib/fs.js

    return;
  }

+  if (options.signal && options.signal.aborted) {


Suggested change

if (options.signal && options.signal.aborted) {

if (options.signal?.aborted) {

nodejs-github-bot · 2020-11-10T09:12:03Z

CI: https://ci.nodejs.org/job/node-test-pull-request/34271/

github-actions · 2020-11-10T14:30:22Z

Landed in 9afe2b6...d9dadac

PR-URL: #35993 Reviewed-By: Antoine du Hamel <duhamelantoine1995@gmail.com> Reviewed-By: Matteo Collina <matteo.collina@gmail.com>

#35993 (comment) PR-URL: #35995 Reviewed-By: Antoine du Hamel <duhamelantoine1995@gmail.com> Reviewed-By: Rich Trott <rtrott@gmail.com>

PR-URL: #35993 Reviewed-By: Antoine du Hamel <duhamelantoine1995@gmail.com> Reviewed-By: Matteo Collina <matteo.collina@gmail.com>

Notable changes: * events: * getEventListeners static (Benjamin Gruenbaum) (#35991) * fs: * support abortsignal in writeFile (Benjamin Gruenbaum) (#35993) * add support for AbortSignal in readFile (Benjamin Gruenbaum) (#35911) * stream: * fix thrown object reference (Gil Pedersen) (#36065) PR URL: #36055

#35993 (comment) PR-URL: #35995 Reviewed-By: Antoine du Hamel <duhamelantoine1995@gmail.com> Reviewed-By: Rich Trott <rtrott@gmail.com>

PR-URL: nodejs#35993 Reviewed-By: Antoine du Hamel <duhamelantoine1995@gmail.com> Reviewed-By: Matteo Collina <matteo.collina@gmail.com>

PR-URL: #35993 Backport-PR-URL: #38386 Reviewed-By: Antoine du Hamel <duhamelantoine1995@gmail.com> Reviewed-By: Matteo Collina <matteo.collina@gmail.com>

Refs: nodejs#33716 Refs: nodejs#35993 Refs: nodejs#35911

Refs: #33716 Refs: #35993 Refs: #35911 PR-URL: #39972 Reviewed-By: Michaël Zasso <targos@protonmail.com> Reviewed-By: Luigi Pinca <luigipinca@gmail.com> Reviewed-By: Juan José Arboleda <soyjuanarbol@gmail.com> Reviewed-By: James M Snell <jasnell@gmail.com> Reviewed-By: Darshan Sen <raisinten@gmail.com> Reviewed-By: Tobias Nießen <tniessen@tnie.de>

PR-URL: #39972 Refs: #33716 Refs: #35993 Refs: #35911 Reviewed-By: Michaël Zasso <targos@protonmail.com> Reviewed-By: Luigi Pinca <luigipinca@gmail.com> Reviewed-By: Juan José Arboleda <soyjuanarbol@gmail.com> Reviewed-By: James M Snell <jasnell@gmail.com> Reviewed-By: Darshan Sen <raisinten@gmail.com> Reviewed-By: Tobias Nießen <tniessen@tnie.de>

Refs: #33716 Refs: #35993 Refs: #35911 PR-URL: #39972 Reviewed-By: Michaël Zasso <targos@protonmail.com> Reviewed-By: Luigi Pinca <luigipinca@gmail.com> Reviewed-By: Juan José Arboleda <soyjuanarbol@gmail.com> Reviewed-By: James M Snell <jasnell@gmail.com> Reviewed-By: Darshan Sen <raisinten@gmail.com> Reviewed-By: Tobias Nießen <tniessen@tnie.de>

nodejs-github-bot added the fs Issues and PRs related to the fs subsystem / file system. label Nov 6, 2020

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fs: replace finally with PromisePrototypeFinally #35995

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fs: support abortsignal in writeFile

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PR-URL: #35993 Reviewed-By: Antoine du Hamel <duhamelantoine1995@gmail.com> Reviewed-By: Matteo Collina <matteo.collina@gmail.com>

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fs: replace finally with PromisePrototypeFinally

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#35993 (comment) PR-URL: #35995 Reviewed-By: Antoine du Hamel <duhamelantoine1995@gmail.com> Reviewed-By: Rich Trott <rtrott@gmail.com>

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fs: support abortsignal in writeFile

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PR-URL: #35993 Reviewed-By: Antoine du Hamel <duhamelantoine1995@gmail.com> Reviewed-By: Matteo Collina <matteo.collina@gmail.com>

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v15.2.0 proposal #36055

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fs: replace finally with PromisePrototypeFinally

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#35993 (comment) PR-URL: #35995 Reviewed-By: Antoine du Hamel <duhamelantoine1995@gmail.com> Reviewed-By: Rich Trott <rtrott@gmail.com>

BethGriggs pushed a commit that referenced this pull request Dec 10, 2020

fs: replace finally with PromisePrototypeFinally

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#35993 (comment) PR-URL: #35995 Reviewed-By: Antoine du Hamel <duhamelantoine1995@gmail.com> Reviewed-By: Rich Trott <rtrott@gmail.com>

BethGriggs pushed a commit that referenced this pull request Dec 15, 2020

fs: replace finally with PromisePrototypeFinally

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#35993 (comment) PR-URL: #35995 Reviewed-By: Antoine du Hamel <duhamelantoine1995@gmail.com> Reviewed-By: Rich Trott <rtrott@gmail.com>

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fs: support abortsignal in writeFile

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PR-URL: nodejs#35993 Reviewed-By: Antoine du Hamel <duhamelantoine1995@gmail.com> Reviewed-By: Matteo Collina <matteo.collina@gmail.com>

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[v14.x] Backport AbortController and friends #38386

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fs: support abortsignal in writeFile

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PR-URL: nodejs#35993 Reviewed-By: Antoine du Hamel <duhamelantoine1995@gmail.com> Reviewed-By: Matteo Collina <matteo.collina@gmail.com>

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fs: support abortsignal in writeFile

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PR-URL: nodejs#35993 Reviewed-By: Antoine du Hamel <duhamelantoine1995@gmail.com> Reviewed-By: Matteo Collina <matteo.collina@gmail.com>

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fs: support abortsignal in writeFile

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PR-URL: #35993 Backport-PR-URL: #38386 Reviewed-By: Antoine du Hamel <duhamelantoine1995@gmail.com> Reviewed-By: Matteo Collina <matteo.collina@gmail.com>

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v14.17.0 proposal #38507

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doc: fix missing history version in fs.md

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Refs: nodejs#33716 Refs: nodejs#35993 Refs: nodejs#35911

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fs: support abortsignal in writeFile #35993

fs: support abortsignal in writeFile #35993

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	if (options.signal && options.signal.aborted) {
	if (options.signal?.aborted) {

fs: support abortsignal in writeFile #35993

fs: support abortsignal in writeFile #35993

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