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test: fix flaky timers-block-eventloop test #18567

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test: fix flaky timers-block-eventloop test #18567

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apapirovski
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@apapirovski apapirovski commented Feb 4, 2018 •
edited

Due to extensive reliance on timings and the fs module, this test
is currently inherently flaky. Refactor it to simply use setImmediate
and only one busy loop.

CI: https://ci.nodejs.org/job/node-test-pull-request/12934/

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

test

@apapirovski
test: fix flaky timers-block-eventloop test
bbfb411 
Due to extensive reliance on timings and the fs module, this test
is currently inherently flaky. Refactor it to simply use setImmediate
and only one busy loop.
@nodejs-github-bot nodejs-github-bot added the test Issues and PRs related to the tests. label Feb 4, 2018
apapirovski
apapirovski commented Feb 4, 2018
View reviewed changes
test/sequential/test-timers-block-eventloop.js
setTimeout(function() {
fs.stat('/dev/nonexistent', () => {
assert(!called);
called = true;
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This is here to prevent an infinite loop before anyone asks :)

@apapirovski
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ping @nodejs/collaborators — this is a test that has failed a few times recently. I would appreciate a review so we can continue making the CI a little less flaky.

mcollina
mcollina approved these changes Feb 6, 2018
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LGTM

@BridgeAR
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BridgeAR commented Feb 6, 2018

Does this really still test the original issue?

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apapirovski commented Feb 6, 2018 •
edited

@BridgeAR yep, just in a very simplified way. It fails on all the same Node versions as the original test case. In fact, the previous test case wasn't even strictly correct which is why it was flaky. Here's an outline of what's going on:

  1. A "now" time gets recorded, let's call it 0
  2. First interval executes (close to no run time), gets added to the back of the interval list with startTime of 0 or 1
  3. Second interval executes, runs for 20ms
  4. We come back to the first interval since it is at the end of the list, the difference between 0 and 0 or 1 is smaller than 10, so it enters the if condition for deferral
  5. it checks the new now value which is now 20+ms ahead of the old now value, so the actual diff is now > 10ms, this means that it sets the timeRemaining to 0 or 1 (depending on whether the bug exists)
  6. If it sets it to 0, then when it comes back to C++, this list fires again and the test case fails

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@BridgeAR Did the explanation above make sense or do you still have concerns about this PR? I would like to land this.

BridgeAR
BridgeAR approved these changes Feb 8, 2018
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Thanks for the detailed description. LGTM

@BridgeAR BridgeAR added the author ready PRs that have at least one approval, no pending requests for changes, and a CI started. label Feb 8, 2018
apapirovski added a commit that referenced this pull request Feb 8, 2018
@apapirovski
test: fix flaky timers-block-eventloop test
6963a93 
Due to extensive reliance on timings and the fs module, this test
is currently inherently flaky. Refactor it to simply use setImmediate
and only one busy loop.

PR-URL: #18567
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
@apapirovski
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Landed in 6963a93

@apapirovski apapirovski closed this Feb 8, 2018
@apapirovski apapirovski deleted the fix-flaky-timers-block-eventloop branch February 8, 2018 20:34
MylesBorins pushed a commit that referenced this pull request Feb 21, 2018
@apapirovski @MylesBorins
test: fix flaky timers-block-eventloop test
59c1cfc 
Due to extensive reliance on timings and the fs module, this test
is currently inherently flaky. Refactor it to simply use setImmediate
and only one busy loop.

PR-URL: #18567
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
MylesBorins pushed a commit that referenced this pull request Feb 21, 2018
@apapirovski @MylesBorins
test: fix flaky timers-block-eventloop test
5d54a04 
Due to extensive reliance on timings and the fs module, this test
is currently inherently flaky. Refactor it to simply use setImmediate
and only one busy loop.

PR-URL: #18567
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
MylesBorins pushed a commit that referenced this pull request Feb 21, 2018
@apapirovski @MylesBorins
test: fix flaky timers-block-eventloop test
af3841b 
Due to extensive reliance on timings and the fs module, this test
is currently inherently flaky. Refactor it to simply use setImmediate
and only one busy loop.

PR-URL: #18567
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
@MylesBorins MylesBorins mentioned this pull request Feb 21, 2018
Merged
MylesBorins pushed a commit that referenced this pull request Feb 21, 2018
@apapirovski @MylesBorins
test: fix flaky timers-block-eventloop test
a667ac1 
Due to extensive reliance on timings and the fs module, this test
is currently inherently flaky. Refactor it to simply use setImmediate
and only one busy loop.

PR-URL: #18567
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
gibfahn pushed a commit that referenced this pull request Apr 13, 2018
@apapirovski @gibfahn
test: fix flaky timers-block-eventloop test
ab8edc9 
Due to extensive reliance on timings and the fs module, this test
is currently inherently flaky. Refactor it to simply use setImmediate
and only one busy loop.

PR-URL: #18567
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
gibfahn pushed a commit that referenced this pull request Apr 13, 2018
@apapirovski @gibfahn
test: fix flaky timers-block-eventloop test
44ab850 
Due to extensive reliance on timings and the fs module, this test
is currently inherently flaky. Refactor it to simply use setImmediate
and only one busy loop.

PR-URL: #18567
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
@MylesBorins MylesBorins mentioned this pull request Apr 13, 2018
Merged
@MylesBorins MylesBorins mentioned this pull request May 2, 2018
Merged
MayaLekova pushed a commit to MayaLekova/node that referenced this pull request May 8, 2018
@apapirovski @MayaLekova
test: fix flaky timers-block-eventloop test
4a1c10f 
Due to extensive reliance on timings and the fs module, this test
is currently inherently flaky. Refactor it to simply use setImmediate
and only one busy loop.

PR-URL: nodejs#18567
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
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@mcollina mcollina mcollina approved these changes

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