test: fix test-cluster-dgram-1 flakiness

[santigimeno]

Checklist

• make -j4 test (UNIX), or vcbuild test nosign (Windows) passes
• commit message follows commit guidelines

Affected core subsystem(s)

test

Description of change

Check for the number of messages received in the exit event listener
instead of the disconnect listener.

Fixes: #8380

[cjihrig]

LGTM

[mhdawson]

Test results on AIX

For the original before the refactor I got 0 failures out of 200 runs.

After the refactor I get 46/150 failures

With this fix the frequency of failures goes done to about 3/150 but it still fails consistently with: (note it says parallel/test-cluster-dgram-3 as opposed to parallel/test-cluster-dgram-1 simply because I copied the new version into a different file for testing).

Mismatched function calls. Expected 10, actual 0.
at worker (/home/iojs/build/workspace/node-test-commit-aix/nodes/aix61-ppc64/test/parallel/test-cluster-dgram-3.js:82:31)
at Object. (/home/iojs/build/workspace/node-test-commit-aix/nodes/aix61-ppc64/test/parallel/test-cluster-dgram-3.js:20:3)
at Module._compile (module.js:409:26)
at Object.Module._extensions..js (module.js:416:10)
at Module.load (module.js:343:32)
at Function.Module._load (module.js:300:12)
at Function.Module.runMain (module.js:441:10)
at startup (node.js:139:18)
at node.js:974:3
assert.js:89
throw new assert.AssertionError({
^
AssertionError: 0 === 10
at Worker. (/home/iojs/build/workspace/node-test-commit-aix/nodes/aix61-ppc64/test/parallel/test-cluster-dgram-3.js:70:14)
at Worker. (/home/iojs/build/workspace/node-test-commit-aix/nodes/aix61-ppc64/test/common.js:401:15)
at emitTwo (events.js:87:13)
at Worker.emit (events.js:172:7)
at ChildProcess. (cluster.js:364:14)
at ChildProcess.g (events.js:260:16)
at emitTwo (events.js:87:13)
at ChildProcess.emit (events.js:172:7)
at Process.ChildProcess._handle.onexit (internal/child_process.js:200:12)

So the next is that it makes things better but does not completely resolve the flakiness at least on AIX.

[santigimeno]

@mhdawson I have pushed a fix. Can you try again? Thanks!

[mhdawson]

@santigimeno that seems to do the trick 0 failures out of 450 so LGTM.

[mhdawson]

CI run: https://ci.nodejs.org/job/node-test-pull-request/3927/

[jasnell]

FWIW, given how this is being fixed, I could be wrong but it looks like the refactor didn't actually break the test as much as highlight a failure that had already been happening but hadn't been caught.

[jasnell]

LGTM

[jasnell]

I'd say given the breakage that the changes in the test are causing in CI, if this is non-controversial we shouldn't need to wait the 48 hours to land. /cc @Trott

[Trott]

Agreed on the "landing sooner than 48 hours" suggestion.

[mhdawson]

landed as 2d2a2d7

[santigimeno]

I understand the hurry, but I was counting on amending the commit message before merging because, after the fixup commit, the fix explanation was different.

[MylesBorins]

This does not land cleanly in LTS. Added dont-land label. Please feel free to manually backport

[santigimeno]

@thealphanerd backport to 4.x here: #9109