Investigate flaky test-dgram-udp6-send-default-host on OS X

@addaleax

Version: master branch
Platform: OS X
Subsystem: test? dgram?

Failure in CI on test of unrelated change: https://ci.nodejs.org/job/node-test-commit-osx/3210/nodes=osx1010/tapTestReport/test.tap-213/

not ok 213 test-dgram-udp6-send-default-host.js
# 
# assert.js:90
#   throw new assert.AssertionError({
#   ^
# AssertionError: message was received correctly
#     at Socket.<anonymous> (/Users/iojs/build/workspace/node-test-commit-osx/nodes/osx1010/test/parallel/test-dgram-udp6-send-default-host.js:29:10)
#     at emitTwo (events.js:106:13)
#     at Socket.emit (events.js:191:7)
#     at UDP.onMessage (dgram.js:532:8)
  ---
  duration_ms: 0.145

/cc @nodejs/testing @addaleax

@mcollina

/cc @mcollina

Stress test: https://ci.nodejs.org/job/node-stress-single-test/687/nodes=osx1010/

Have seen this failure locally a couple of times though I cannot reproduce it consistently :/.
Maybe use assert.strictEqual here would help to find out what's going on.

@santigimeno

@santigimeno Yup, I had the same thought and am putting in the PR for that right now...

test: improve assert message for debugging

#6581

This is fairly unexpected, as the ipv4 equivalent of this test is not flaky.

Is this flaky only on Mac? Hopefully #6581 should tell what's happening. I have never seen it fail here.

test: improve assert message for debugging

It looks like the problem is that sometimes the messages are not received in order, which makes sense being UDP. See output from https://ci.nodejs.org/job/node-stress-single-test/nodes=osx1010/690 :

not ok 1 test-dgram-udp6-send-default-host.js
# 
# assert.js:90
#   throw new assert.AssertionError({
#   ^
# AssertionError: 'hello' === 'yyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyy
#     at Socket.<anonymous> (/Users/iojs/build/workspace/node-stress-single-test/nodes/osx1010/test/parallel/test-dgram-udp6-send-default-host.js:29:10)
#     at emitTwo (events.js:106:13)
#     at Socket.emit (events.js:191:7)
#     at UDP.onMessage (dgram.js:532:8)
  ---
  duration_ms: 0.139

Could it be that the kernel decides to reorder the packets here for some reason? That’s allowed, although I can’t see why it would. But it would explain why the test is flaky and why this is an OS-specific issue.

@addaleax

@addaleax Some comments here like this suggest that could be the reason

👍 I guess the IPv4 test has a chance of being flaky too, then?

Is there an equivalent IPv4 test? I can't find it.

@santigimeno

@santigimeno test/parallel/test-dgram-send-default-host.js

@addaleax

@addaleax Thanks! I guess it should also be rewritten

test: allow out-of-order replies in dgram tests

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Investigate flaky test-dgram-udp6-send-default-host on OS X #6577

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Investigate flaky test-dgram-udp6-send-default-host on OS X #6577

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Trott commented on May 4, 2016

Trott commented on May 4, 2016

santigimeno commented on May 4, 2016

Trott commented on May 4, 2016

Trott commented on May 4, 2016

mcollina commented on May 5, 2016

santigimeno commented on May 5, 2016

addaleax commented on May 5, 2016

santigimeno commented on May 5, 2016

addaleax commented on May 5, 2016

santigimeno commented on May 5, 2016

addaleax commented on May 5, 2016

santigimeno commented on May 5, 2016

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