fs: do not emit 'stop' watch event synchronously #8524

claudiorodriguez · 2016-09-13T22:13:14Z

Checklist

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

Affected core subsystem(s)

Description of change

Emits 'stop' event for fs.watchFile on process.nextTick
to fix 'maximum call stack size exceeded' error when
stop is called synchronously after listener is attached.

Fixes: #8421

cjihrig · 2016-09-13T22:23:23Z

LGTM pending CI.

mscdex · 2016-09-13T22:57:09Z

CI: https://ci.nodejs.org/job/node-test-pull-request/4038/

imyller · 2016-09-14T12:39:48Z

@claudiorodriguez Just wondering if setImmediate instead of nextTick should be used here?

https://github.com/nodejs/node/blob/master/doc/topics/the-event-loop-timers-and-nexttick.md#processnexttick-vs-setimmediate states that:

We recommend developers use setImmediate() in all cases because it's easier to reason about (and it leads to code that's compatible with a wider variety of environments, like browser JS.)

setImmediate is bit more asynchronous since it fires on the following iteration or 'tick' of the event loop; meaning that stop event would be emitted there.

I noted that nextTick is the preferred solution in core lib/. Maybe for a good reason.

claudiorodriguez · 2016-09-15T07:51:43Z

@imyller just tried that change locally, it passes all tests successfully. I'd be inclined to make the change, it makes sense, although maybe someone from @nodejs/collaborators can chime in, if process.nextTick is preferred for a particular reason.

bnoordhuis · 2016-09-15T08:08:53Z

process.nextTick() is lower latency, it's dispatched as quickly as possible. setImmediate() postpones the callback until the next loop tick.

(process.nextTick() was an apt name when it was introduced but not anymore.)

yorkie · 2016-09-15T11:55:20Z

@claudiorodriguez 2 suggestions from me:

the test file should be renamed to test-fs-watch-stop-sync.js.
we should also add a test file test-fs-watch-stop-async.js to make sure that the trigger calls emit() in next ticks.

jasnell

While I'm good with this change in general, I'm wondering if this needs to be semver-major due to the change in timing? I don't believe it does but want to be careful

claudiorodriguez · 2016-09-16T07:47:52Z

@yorkie good idea, I'll do that this weekend

@jasnell I'm trying to think of a way in which userland code listening to the emitter would break, but can't think of any - seeing as how the contract remains the same. Can you think of any user code that would behave differently?

claudiorodriguez · 2016-09-19T08:21:52Z

@yorkie added the test, PTAL

New CI: https://ci.nodejs.org/job/node-test-pull-request/4123/
(although CI seems to have been failing for a while)

mcollina · 2016-09-19T08:28:38Z

lib/fs.js

-    self.emit('stop');
+    process.nextTick(function() {
+      self.emit('stop');
+    });


Can we avoid allocating a new closure here? When calling stop() on a massive tree of objects, we will be allocating a lot of closures for nothing.

this._handle.onstop = function() { process.nextTick(emitStop, self) } // to be put a root level function emitStop(self) { self.emit('stop'); }

@mcollina changed, PTAL

Emits 'stop' event for fs.watchFile on process.nextTick to fix 'maximum call stack size exceeded' error when `stop` is called synchronously after listener is attached. Fixes: nodejs#8421

imyller

LGTM

jasnell · 2016-09-20T18:21:36Z

@claudiorodriguez ... no, I can't think of anything either. As I said, this should be perfectly fine.

jasnell

LGTM

jasnell · 2016-09-22T17:40:05Z

New CI: https://ci.nodejs.org/job/node-test-pull-request/4222/

yorkie

LGTM :)

imyller · 2016-09-23T22:23:43Z

Landing:

Five LGTMs
No objections
CI test passed (only the known CI failures)

/ping @jasnell you were thinking about adding semver-major label for this. Still relevant?

Emits 'stop' event for fs.watchFile on process.nextTick to fix 'maximum call stack size exceeded' error when `stop` is called synchronously after listener is attached. PR-URL: nodejs#8524 Fixes: nodejs#8421 Reviewed-By: Colin Ihrig <cjihrig@gmail.com> Reviewed-By: Matteo Collina <matteo.collina@gmail.com> Reviewed-By: Ilkka Myller <ilkka.myller@nodefield.com> Reviewed-By: James M Snell <jasnell@gmail.com> Reviewed-By: Yorkie Liu <yorkiefixer@gmail.com>

imyller · 2016-09-23T22:27:13Z

landed in 1b97774

imyller · 2016-09-23T22:38:32Z

To be safe, I've added dont-land- labels until semver level is discussed and resolved.

Emits 'stop' event for fs.watchFile on process.nextTick to fix 'maximum call stack size exceeded' error when `stop` is called synchronously after listener is attached. PR-URL: #8524 Fixes: #8421 Reviewed-By: Colin Ihrig <cjihrig@gmail.com> Reviewed-By: Matteo Collina <matteo.collina@gmail.com> Reviewed-By: Ilkka Myller <ilkka.myller@nodefield.com> Reviewed-By: James M Snell <jasnell@gmail.com> Reviewed-By: Yorkie Liu <yorkiefixer@gmail.com>

addaleax · 2016-10-01T21:07:08Z

Hm, bump? Does anybody feel this should be semver-major? If not, I’d like to remove the labels.

Fishrock123 · 2016-10-01T21:11:39Z

Changes event timing, sounds major to me

nodejs-github-bot added the fs Issues and PRs related to the fs subsystem / file system. label Sep 13, 2016

jasnell reviewed Sep 15, 2016

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claudiorodriguez force-pushed the fs-stop-nexttick branch from b6b1a55 to df27869 Compare September 19, 2016 08:20

mcollina reviewed Sep 19, 2016

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fs: do not emit 'stop' watch event synchronously

e4028ac

Emits 'stop' event for fs.watchFile on process.nextTick to fix 'maximum call stack size exceeded' error when `stop` is called synchronously after listener is attached. Fixes: nodejs#8421

claudiorodriguez force-pushed the fs-stop-nexttick branch from df27869 to e4028ac Compare September 19, 2016 08:50

mcollina approved these changes Sep 19, 2016

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imyller approved these changes Sep 19, 2016

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jasnell approved these changes Sep 20, 2016

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Trott force-pushed the master branch from b0df363 to c5ce7f4 Compare September 21, 2016 00:09

yorkie approved these changes Sep 23, 2016

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imyller self-assigned this Sep 23, 2016

imyller closed this Sep 23, 2016

imyller removed their assignment Sep 23, 2016

imyller added dont-land-on-v6.x labels Sep 23, 2016

Fishrock123 added the semver-major PRs that contain breaking changes and should be released in the next major version. label Oct 1, 2016

gibfahn mentioned this pull request Jun 15, 2017

Auditing for 6.11.1 nodejs/Release#230

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fs: do not emit 'stop' watch event synchronously #8524

fs: do not emit 'stop' watch event synchronously #8524

claudiorodriguez commented Sep 13, 2016 •

edited

cjihrig commented Sep 13, 2016

mscdex commented Sep 13, 2016

imyller commented Sep 14, 2016

claudiorodriguez commented Sep 15, 2016

bnoordhuis commented Sep 15, 2016

yorkie commented Sep 15, 2016

jasnell left a comment

claudiorodriguez commented Sep 16, 2016 •

edited

claudiorodriguez commented Sep 19, 2016

mcollina Sep 19, 2016

claudiorodriguez Sep 19, 2016

imyller left a comment

jasnell commented Sep 20, 2016

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jasnell commented Sep 22, 2016

yorkie left a comment

imyller commented Sep 23, 2016

imyller commented Sep 23, 2016

imyller commented Sep 23, 2016

addaleax commented Oct 1, 2016

Fishrock123 commented Oct 1, 2016

fs: do not emit 'stop' watch event synchronously #8524

fs: do not emit 'stop' watch event synchronously #8524

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claudiorodriguez commented Sep 13, 2016 • edited

Checklist

Affected core subsystem(s)

Description of change

cjihrig commented Sep 13, 2016

mscdex commented Sep 13, 2016

imyller commented Sep 14, 2016

claudiorodriguez commented Sep 15, 2016

bnoordhuis commented Sep 15, 2016

yorkie commented Sep 15, 2016

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claudiorodriguez commented Sep 16, 2016 • edited

claudiorodriguez commented Sep 19, 2016

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imyller commented Sep 23, 2016

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imyller commented Sep 23, 2016

addaleax commented Oct 1, 2016

Fishrock123 commented Oct 1, 2016

claudiorodriguez commented Sep 13, 2016 •

edited

claudiorodriguez commented Sep 16, 2016 •

edited