Tests hang frequently in XenAPIVMTestCase.test_parallel_builds

Seems to me that this is when the test should be failing, however it doesn't assert anything and just hangs instead. Perhaps just add a timeout where it's calling .wait() and fail if it doesn't in time? Seems risky to me, and that also means we need to make it work.

I say nuke the test!

Adding eventlet.monkey_patch() to the top of the test file seemed to squash this for me, but I'm hesitant to say definitively because it's not consistently reproducible.

Nevermind, I was just getting lucky.

I bet it's this (a similar backtrace is in Soren's log):

2011-08-28 11:01:52,770 DEBUG nova.virt.xenapi.fake [-] Calling VM.start <bound
method FakeSessionForVMTests.VM_start of <nova.tests.xenapi.stubs.FakeSessionFor
VMTests object at 0x1077cb4c>> from (pid=9342) callit /opt/jenkins/workspace/uni
t-nova/upstream/nova/virt/xenapi/fake.py:431
2011-08-28 11:01:52,772 DEBUG nova.virt.xenapi.vmops [-] Starting instance 2 fro
m (pid=9342) _start /opt/jenkins/workspace/unit-nova/upstream/nova/virt/xenapi/v
mops.py:134
Traceback (most recent call last):
  File "/opt/jenkins/workspace/unit-nova/upstream/.nova-venv/lib/python2.6/site-
packages/eventlet/hubs/hub.py", line 336, in fire_timers
    timer()
2011-08-28 11:01:52,773 DEBUG nova.virt.xenapi.fake [-] Calling VM.start <bound
method FakeSessionForVMTests.VM_start of <nova.tests.xenapi.stubs.FakeSessionFor
VMTests object at 0x1077cb4c>> from (pid=9342) callit /opt/jenkins/workspace/uni
t-nova/upstream/nova/virt/xenapi/fake.py:431
  File "/opt/jenkins/workspace/unit-nova/upstream/.nova-venv/lib/python2.6/site-
packages/eventlet/hubs/timer.py", line 56, in __call__
    cb(*args, **kw)
  File "/opt/jenkins/workspace/unit-nova/upstream/.nova-venv/lib/python2.6/site-
packages/eventlet/semaphore.py", line 95, in _do_acquire
    waiter.switch()
error: cannot switch to a different thread

The traceback from Soren's log:

Traceback (most recent call last):
  File "/usr/lib/python2.7/dist-packages/eventlet/hubs/hub.py", line 336, in fire_timers
2011-08-22 21:58:29,483 DEBUG nova.virt.xenapi.fake [-] Calling host.call_plugin <bound method FakeSessionForVMTests.host_call_plugin of <nova.tests.xenapi.stubs.FakeSessionForVMTests object at 0x1365f490>> from (pid=4594) callit /home/soren/src/openstack/nova/virt-layer-cleanup2/nova/virt/xenapi/fake.py:428
    timer()
  File "/usr/lib/python2.7/dist-packages/eventlet/hubs/timer.py", line 56, in __call__
    cb(*args, **kw)
  File "/usr/lib/python2.7/dist-packages/eventlet/semaphore.py", line 95, in _do_acquire
    waiter.switch()
error: cannot switch to a different thread