Eliminate errors from calling ChromeLauncher.kill() twice #1131

Janpot · 2016-12-09T10:16:07Z

The error happened outside the Promise chain and is uncatchable.

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Janpot · 2016-12-09T10:31:22Z

I signed it!

googlebot · 2016-12-09T10:31:24Z

CLAs look good, thanks!

wardpeet · 2016-12-09T11:39:46Z

can you tell us when this exactly happens?

Janpot · 2016-12-09T13:04:13Z

reproducible when doing

launcher.kill();
launcher.kill();

Nobody would ever do exactly this but in some flows this might happen. In my particular case I had set up a SIGINT handler that kills the launcher. Then set up development with nodemon, which sends a SIGINT when it's restarting. But in the case of manually interrupting nodemon the signal gets sent twice.

Regardless of this corner case though, the existing code has a possibility of throwing an error that can't be caught by any consuming code. closeSync can throw.

In the kill() method there is a comment

// fail silently as we did not start chrome

The fact that this comment exists means to me that trying to kill a non-running launcher is defined behavior. And the behavior is 'fail silently', which I implemented for the case where you try to kill an already killed launcher.

There's also other ways of fixing this:

set this.outFile = null; and this.errFile = null; after closing them.
set this.chrome = null; at the end of the kill method.

wardpeet · 2016-12-09T23:43:25Z

I would go for

set this.outFile = null; and this.errFile = null; after closing them.
set this.chrome = null; at the end of the kill method.

Than we can keep everything sync :)

brendankenny · 2016-12-10T00:05:39Z

There's also other ways of fixing this:

set this.outFile = null; and this.errFile = null; after closing them.

set this.chrome = null; at the end of the kill method.

even if you went the way of the current PR these should really be nulled after closing anyways, so it would be great to go that way

Janpot · 2016-12-10T09:08:18Z

@wardpeet is there any specific reason you prefer the sync methods over the async ones? The main reason why I changed this code is because I want to be able to handle the errors that might possibly be thrown by closeSync. Using promises to do that there just felt more natural to me. Would you rather want me to use a try {} catch {} and the closeSync method instead?

wardpeet · 2016-12-10T11:01:29Z

It's only my personal experience if you don't use async await, promises make your code more complex than using plain sync when it's not necessary.

* add nulling of properties * make synchronous again

Janpot · 2016-12-10T16:14:09Z

I disagree, but I don't think it's worth starting an argument over. I updated it, can you take another look?

brendankenny

it could be good to add a unit test that we avoid this error, but we can do that in a future PR if you'd rather move forward with the scope of this one.

brendankenny · 2016-12-13T02:10:11Z

lighthouse-cli/chrome-launcher.ts

-    if (this.outFile) {
-      fs.closeSync(this.outFile);
-    }
+    try {


I'd rather avoid the try/catch since it'll silently eat errors, but is it even necessary? This is the only place that these files are closed, so the conditionals should guard against attempting to delete with already-closed file descriptor.

wrapped the whole function in the promise, instead of only rimraf

Janpot · 2016-12-13T10:19:40Z

@brendankenny Added a test

brendankenny

a few last style nits

brendankenny · 2016-12-13T22:07:17Z

lighthouse-cli/chrome-launcher.ts

-      rimraf(this.TMP_PROFILE_DIR, function() {
-        resolve();
-      });
+      rimraf(this.TMP_PROFILE_DIR, () => resolve());


nit: this can be just rimraf(this.TMP_PROFILE_DIR, () => resolve());

did you mean rimraf(this.TMP_PROFILE_DIR, resolve);? I chose the former because the return type is Promise<undefined> and the callback to rimraf could return with an error.

ah, good point, SGTM as is

brendankenny · 2016-12-13T22:07:36Z

lighthouse-cli/test/cli/chrome-launcher-test.js

+
+const ChromeLauncher = require('../../chrome-launcher.js').ChromeLauncher;
+
+/* global describe, it */


use /* eslint-env mocha */ instead

That's what I usually use but /* global describe, it */ is all over the code base.

yeah, sorry, that's legacy stuff that's slowly getting changed over as those files are touched :)

I can replace it everywhere if you want, or would that clutter this PR too much?

yeah, I generally prefer keeping PRs contained and we can have a separate PR for that (and/or change as we go since it's functionally equivalent)

brendankenny · 2016-12-13T22:11:45Z

lighthouse-cli/test/cli/chrome-launcher-test.js

+    const chromeInstance = new ChromeLauncher();
+    chromeInstance.prepare();
+    chromeInstance.run();
+    return chromeInstance.waitUntilReady()


I believe you can do just

const chromeInstance = new ChromeLauncher(); return chromeInstance.run() .then(() => { ...

Ok, it was like that in manual-chrome-launcher. Can change there as well?

sounds good

er, I think it's fine as is. I'd rather avoid touching it so we can land this change

chromeInstance.run() also waits on waitUntilReady() internally, so it isn't necessary to call chromeInstance.waitUntilReady() explicitly

brendankenny · 2016-12-13T22:11:51Z

lighthouse-cli/test/cli/chrome-launcher-test.js

+      .then(() => {
+        return Promise.all([
+          chromeInstance.kill(),
+          chromeInstance.kill()


Janpot · 2016-12-13T23:00:55Z

feel free to cancel https://travis-ci.org/GoogleChrome/lighthouse/builds/183750931 to clear up queue

brendankenny

LGTM

Thanks!

…me#1131)

Calling .kill() twice results in EBADF error in closeSync

588e7a9

The error happened outside the Promise chain and is uncatchable.

Typescript still a bit new to me :)

b54eb02

Small indentation fix

f629793

Janpot added 2 commits December 10, 2016 17:10

Address feedback.

1a0b107

* add nulling of properties * make synchronous again

Put old code back

0abc750

wardpeet approved these changes Dec 12, 2016

View reviewed changes

brendankenny requested changes Dec 13, 2016

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Janpot added 3 commits December 13, 2016 08:16

wrap everything in the promise

f7da7dd

Add test

e2b3242

Support older node versions

03cdb9c

brendankenny changed the title ~~Calling .kill() twice results in EBADF error in closeSync~~ Eliminate errors from calling ChromeLauncher.kill() twice Dec 13, 2016

brendankenny requested changes Dec 13, 2016

View reviewed changes

Janpot added 2 commits December 13, 2016 23:36

Fix some style issues

ffec156

I should really pay more attention to code reviews

365c1c0

brendankenny approved these changes Dec 14, 2016

View reviewed changes

paulirish approved these changes Dec 14, 2016

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brendankenny merged commit 215215e into GoogleChrome:master Dec 14, 2016

Janpot deleted the killerror branch December 14, 2016 07:27

andrewrota pushed a commit to andrewrota/lighthouse that referenced this pull request Jan 13, 2017

Eliminate errors from calling ChromeLauncher.kill() twice (GoogleChro…

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…me#1131)

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Eliminate errors from calling ChromeLauncher.kill() twice #1131

Eliminate errors from calling ChromeLauncher.kill() twice #1131

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		const ChromeLauncher = require('../../chrome-launcher.js').ChromeLauncher;

		/* global describe, it */

Eliminate errors from calling ChromeLauncher.kill() twice #1131

Eliminate errors from calling ChromeLauncher.kill() twice #1131

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Janpot commented Dec 9, 2016

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