investigate potentially flaky test on centos

[jasnell]

https://ci.nodejs.org/job/node-test-commit-linux/1215/nodes=centos5-32/console

not ok 61 test-child-process-spawnsync-input.js
#
#assert.js:89
#  throw new assert.AssertionError({
#  ^
#AssertionError: <Buffer > deepEqual <Buffer 74 68 69 73 20 69 73 20 73 74 64 6f 75 74 0a>
#    at Object.<anonymous> (/home/iojs/build/workspace/node-test-commit-linux/nodes/centos5-32/test/parallel/test-child-process-spawnsync-input.js:98:8)
#    at Module._compile (module.js:423:26)
#    at Object.Module._extensions..js (module.js:430:10)
#    at Module.load (module.js:354:32)
#    at Function.Module._load (module.js:311:12)
#    at Function.Module.runMain (module.js:455:10)
#    at startup (node.js:138:18)
#    at node.js:974:3

I've seen this before, only on centos.

[cjihrig]

I wonder if this failed assertion is even really necessary. The assertion is verifying that we can successfully get a result buffer larger than the user specified max buffer size. Maybe someone who was more involved with the project when the test was originally written can give more perspective, but it seems unnecessary to me.

[Trott]

Here's the commit that introduced that line of code on the test: e8df267

¯\_(ツ)_/¯

[Trott]

Definitely flaky: https://ci.nodejs.org/job/node-stress-single-test/nodes=centos5-32/5/console

[Trott]

FWIW, I split out the flaky part of the test file from the rest of the test file. The flaky part still fails in the stress test, and the non-flaky part looks like it's going to complete it's run with no failures. So, at least, that would seem to rule out a side effect from the rest of the file. The issue, whatever it is, is triggered by just the narrow test at the end of the file.

[Trott]

The problem here seems like a race condition. Most of the time, stdout flushes before spawnSync() completes but every once in a while, either stdout does not flush or it just drops/loses stuff for whatever reason. That's my guess anyway. Not sure yet how to proceed to confirm or refute the theory...

[Trott]

Maybe related?: nodejs/node-v0.x-archive#8329

[Trott]

#3889 fixes this flaky test.