Flaky test-timers-block-eventloop

Test added in #15072

Example failure:
https://ci.nodejs.org/job/node-test-commit-linuxone/9533/nodes=rhel72-s390x/console

not ok 1945 sequential/test-timers-block-eventloop
  ---
  duration_ms: 0.440
  severity: fail
  stack: |-
    assert.js:45
      throw new errors.AssertionError({
      ^
    
    AssertionError [ERR_ASSERTION]: eventloop blocked!
        at Timeout.mustNotCall [as _onTimeout] (/data/iojs/build/workspace/node-test-commit-linuxone/nodes/rhel72-s390x/test/common/index.js:571:12)
        at ontimeout (timers.js:478:11)
        at tryOnTimeout (timers.js:302:5)
        at Timer.listOnTimeout (timers.js:262:5)
  ...

/cc @nodejs/platform-s390

I guess the reported error is on RHEL on S390

@targos

@targos and @gireeshpunathil
I reproduce this at my laptop(thinkpad x240/ubuntu 16.04) with the following steps:

start 4 processes to occupy the cpu while(1);
run the test case every other second.
the error may happen every 10 times running the case.

So I guess maybe the test server was busy when this happens.

Fix is easy: just change the t3 timeout to 200ms.

--- a/test/sequential/test-timers-block-eventloop.js
+++ b/test/sequential/test-timers-block-eventloop.js
@@ -11,7 +11,7 @@ const t2 = setInterval(() => {
   common.busyLoop(15);
 }, 10);
 
-const t3 = setTimeout(common.mustNotCall('eventloop blocked!'), 100);
+const t3 = setTimeout(common.mustNotCall('eventloop blocked!'), 200);

With this fix, failures does not happen after 1000 times running. Is a PR needed?

@zhangzifa

@zhangzifa - makes sense, the test seem to be walking on a ridge with high sensitivity on the timing of events that does not account into the environmental factors in the system. While we wait to hear from @nodejs/platform-s390 this experiment and the proposal thereon looks reasonable to me, thanks!

@jBarz

@jBarz can you take a look and comment.

@zhangzifa

It seems like we are depending on the following fs.stat call to callback within 50 milliseconds. Otherwise the test fails.

fs.stat('./nonexistent.txt', (err, stats) => {...}

Increasing the timeout is one way to fix this.
@zhangzifa , could we stat something like /dev/zero which won't depend on the speed of the filesystem mount?

@jBarz

@jBarz I tested just now with /dev/zero, anyway, it still fails occasionally when cpu is busy. Anyway, I will update the case to /dev/nonexistent

@zhangzifa

@zhangzifa a PR would be great.

@gibfahn

@gibfahn 16314 is there now.

test: update test-timers-block-eventloop.js

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Flaky test-timers-block-eventloop #16310

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Flaky test-timers-block-eventloop #16310

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gireeshpunathil commented on Oct 19, 2017

gireeshpunathil commented on Oct 19, 2017

zhangzifa commented on Oct 19, 2017

zhangzifa commented on Oct 19, 2017

gireeshpunathil commented on Oct 19, 2017

mhdawson commented on Oct 19, 2017

jBarz commented on Oct 20, 2017

zhangzifa commented on Oct 20, 2017

gibfahn commented on Oct 20, 2017

zhangzifa commented on Oct 20, 2017

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