Don't log GreenletExit in ServiceLauncher if any thread is killed on wait()

[Ihar Hrachyshka]

This is similar to bug 1282206 that fixed the same issue for ProcessLauncher.

The failure shows up in gate (Icehouse, Juno) as follows:

ft1.1683: tests.unit.test_service.ServiceRestartTest.test_service_restart_StringException: Traceback (most recent call last):
  File "tests/unit/test_service.py", line 252, in test_service_restart
    ready = self._spawn_service()
  File "tests/unit/test_service.py", line 244, in _spawn_service
    launcher.wait(ready_callback=ready_event.set)
  File "openstack/common/service.py", line 196, in wait
    status, signo = self._wait_for_exit_or_signal(ready_callback)
  File "openstack/common/service.py", line 182, in _wait_for_exit_or_signal
    self.stop()
  File "openstack/common/service.py", line 128, in stop
    self.services.stop()
  File "openstack/common/service.py", line 479, in stop
    self.tg.stop()
  File "openstack/common/threadgroup.py", line 125, in stop
    self._stop_threads()
  File "openstack/common/threadgroup.py", line 98, in _stop_threads
    x.stop()
  File "openstack/common/threadgroup.py", line 44, in stop
    self.thread.kill()
  File "/home/jenkins/workspace/gate-oslo-incubator-python26/.tox/py26/lib/python2.6/site-packages/eventlet/greenthread.py", line 238, in kill
    return kill(self, *throw_args)
  File "/home/jenkins/workspace/gate-oslo-incubator-python26/.tox/py26/lib/python2.6/site-packages/eventlet/greenthread.py", line 292, in kill
    g.throw(*throw_args)
  File "/home/jenkins/workspace/gate-oslo-incubator-python26/.tox/py26/lib/python2.6/site-packages/eventlet/greenthread.py", line 212, in main
    result = function(*args, **kwargs)
  File "/home/jenkins/workspace/gate-oslo-incubator-python26/.tox/py26/lib/python2.6/site-packages/eventlet/greenthread.py", line 278, in just_raise
    raise greenlet.GreenletExit()
GreenletExit
Traceback (most recent call last):
_StringException: Empty attachments:
  pythonlogging:''
  stderr
  stdout

traceback-1: {{{
Traceback (most recent call last):
  File "tests/unit/test_service.py", line 93, in _reap_pid
    if self.pid:
AttributeError: 'ServiceRestartTest' object has no attribute 'pid'
}}}

Traceback (most recent call last):
  File "tests/unit/test_service.py", line 252, in test_service_restart
    ready = self._spawn_service()
  File "tests/unit/test_service.py", line 244, in _spawn_service
    launcher.wait(ready_callback=ready_event.set)
  File "openstack/common/service.py", line 196, in wait
    status, signo = self._wait_for_exit_or_signal(ready_callback)
  File "openstack/common/service.py", line 182, in _wait_for_exit_or_signal
    self.stop()
  File "openstack/common/service.py", line 128, in stop
    self.services.stop()
  File "openstack/common/service.py", line 479, in stop
    self.tg.stop()
  File "openstack/common/threadgroup.py", line 125, in stop
    self._stop_threads()
  File "openstack/common/threadgroup.py", line 98, in _stop_threads
    x.stop()
  File "openstack/common/threadgroup.py", line 44, in stop
    self.thread.kill()
  File "/home/jenkins/workspace/gate-oslo-incubator-python26/.tox/py26/lib/python2.6/site-packages/eventlet/greenthread.py", line 238, in kill
    return kill(self, *throw_args)
  File "/home/jenkins/workspace/gate-oslo-incubator-python26/.tox/py26/lib/python2.6/site-packages/eventlet/greenthread.py", line 292, in kill
    g.throw(*throw_args)
  File "/home/jenkins/workspace/gate-oslo-incubator-python26/.tox/py26/lib/python2.6/site-packages/eventlet/greenthread.py", line 212, in main
    result = function(*args, **kwargs)
  File "/home/jenkins/workspace/gate-oslo-incubator-python26/.tox/py26/lib/python2.6/site-packages/eventlet/greenthread.py", line 278, in just_raise
    raise greenlet.GreenletExit()
GreenletExit

Logs: http://logs.openstack.org/82/129182/1/check/gate-oslo-incubator-python26/002df95/testr_results.html.gz

[Ihar Hrachyshka (ihar-hrachyshka)]

I've sent https://review.openstack.org/129278 to check whether this is a similar problem as in bug 1282206.

[Numan Siddique (numansiddique)]

I wasn't aware of it that you are working

[Ihar Hrachyshka (ihar-hrachyshka)]

The problem is not about ServiceLauncher failure, but about GreenletExit exception logged on thread kill with LOG.exception() even though it's expected behaviour when killing a greenthread. As for the test failure, it's because the unit test class does not guard correctly against potential leakage of spawned pids into test environment.

So two patches are relevant here:
- don't log GreenletExit in ThreadGroup: https://review.openstack.org/130799
- test resilience: https://review.openstack.org/129278