Investigate flaky test test-debug-signal-cluster

[joaocgreis]

Examples of failures:

• smartos14-64

[jbergstroem]

here's example output:

not ok 150 test-debug-signal-cluster.js
# got pids [98570,98575,98576]
# 
# assert.js:89
# throw new assert.AssertionError({
# ^
# AssertionError: test timed out.
# at testTimedOut [as _onTimeout] (/home/iojs/build/workspace/node-test-commit-smartos/nodes/smartos14-32/test/parallel/test-debug-signal-cluster.js:54:3)
# at Timer.unrefdHandle (timers.js:301:14)
# > all workers are running
# > Starting debugger agent.
# > Debugger listening on port 12388
# > Starting debugger agent.
# > Starting debugger agent.
# > Debugger listening on port 12389Debugger listening on port 12390

[jbergstroem]

Looks out some output buffering issue..

[Trott]

When this happens, the line Debugger listening on port 12389Debugger listening on port 12390 has two line feeds at the end. So, somehow, a \n is being misplaced to the end of both lines rather than between the 9 and the D...

[Trott]

In lib/_debugAgent.js, changing this...

process._rawDebug('Debugger listening on port %d', addr.port);

...to this...

console.error('Debugger listening on port %d', addr.port);

makes the test pass 1000 times in a row. Previous runs got 50-100 failures every 1000 runs.

Here it is running 1000 times in a row successfully:
https://ci.nodejs.org/job/node-test-commit-smartos/182/

And here is a more typical run with the current code base. 1000 times in a row with around a dozen failures on each SmartOS:
https://ci.nodejs.org/job/node-test-commit-smartos/170/

Running tests right now to see if this change blows up any of the other tests and it looks good. PR coming in a few minutes...

[Trott]

Update: Looks like it blows up on Windows. Easy enough to deal with. PR still coming in a little bit...

[Trott]

PR: #3615