The problem happens if the nova compute service is restarted. This at times has a situation where is is impossible to restart the nova compute service. We should consider changing this to critical. Please see the trace below when I restarted the compute service:

2013-09-02 00:59:40.979 INFO nova.compute.manager [req-10927006-b0e9-4159-9032-6337bbad97e5 None None] Updating host status
Traceback (most recent call last):
  File "/usr/local/lib/python2.7/dist-packages/eventlet/hubs/poll.py", line 97, in wait
    readers.get(fileno, noop).cb(fileno)
  File "/usr/local/lib/python2.7/dist-packages/eventlet/greenthread.py", line 194, in main
    result = function(*args, **kwargs)
  File "/opt/stack/nova/nova/openstack/common/service.py", line 65, in run_service
    service.start()
  File "/opt/stack/nova/nova/service.py", line 154, in start
    self.manager.init_host()
  File "/opt/stack/nova/nova/compute/manager.py", line 757, in init_host
    self._report_driver_status(context)
  File "/opt/stack/nova/nova/compute/manager.py", line 4409, in _report_driver_status
    capabilities = self.driver.get_host_stats(refresh=True)
  File "/opt/stack/nova/nova/virt/vmwareapi/driver.py", line 363, in get_host_stats
    return self.host_state.get_host_stats(refresh=refresh)
  File "/opt/stack/nova/nova/virt/vmwareapi/driver.py", line 434, in host_state
    self._cluster)
  File "/opt/stack/nova/nova/virt/vmwareapi/host.py", line 155, in __init__
    self.update_status()
  File "/opt/stack/nova/nova/virt/vmwareapi/host.py", line 201, in update_status
    summary.quickStats.overallMemoryUsage
AttributeError: 'Text' object has no attribute 'overallMemoryUsage'
Removing descriptor: 7
2013-09-02 00:59:41.382 ERROR nova.openstack.common.threadgroup [-] 'Text' object has no attribute 'overallMemoryUsage'
2013-09-02 00:59:41.382 TRACE nova.openstack.common.threadgroup Traceback (most recent call last):
2013-09-02 00:59:41.382 TRACE nova.openstack.common.threadgroup   File "/opt/stack/nova/nova/openstack/common/threadgroup.py", line 117, in wait
2013-09-02 00:59:41.382 TRACE nova.openstack.common.threadgroup     x.wait()
2013-09-02 00:59:41.382 TRACE nova.openstack.common.threadgroup   File "/opt/stack/nova/nova/openstack/common/threadgroup.py", line 49, in wait
2013-09-02 00:59:41.382 TRACE nova.openstack.common.threadgroup     return self.thread.wait()
2013-09-02 00:59:41.382 TRACE nova.openstack.common.threadgroup   File "/usr/local/lib/python2.7/dist-packages/eventlet/greenthread.py", line 168, in wait
2013-09-02 00:59:41.382 TRACE nova.openstack.common.threadgroup     return self._exit_event.wait()
2013-09-02 00:59:41.382 TRACE nova.openstack.common.threadgroup   File "/usr/local/lib/python2.7/dist-packages/eventlet/event.py", line 116, in wait
2013-09-02 00:59:41.382 TRACE nova.openstack.common.threadgroup     return hubs.get_hub().switch()
2013-09-02 00:59:41.382 TRACE nova.openstack.common.threadgroup   File "/usr/local/lib/python2.7/dist-packages/eventlet/hubs/hub.py", line 187, in switch
2013-09-02 00:59:41.382 TRACE nova.openstack.common.threadgroup     return self.greenlet.switch()
2013-09-02 00:59:41.382 TRACE nova.openstack.common.threadgroup   File "/usr/local/lib/python2.7/dist-packages/eventlet/greenthread.py", line 194, in main
2013-09-02 00:59:41.382 TRACE nova.openstack.common.threadgroup     result = function(*args, **kwargs)
2013-09-02 00:59:41.382 TRACE nova.openstack.common.threadgroup   File "/opt/stack/nova/nova/openstack/common/service.py", line 65, in run_service
2013-09-02 00:59:41.382 TRACE nova.openstack.common.threadgroup     service.start()
2013-09-02 00:59:41.382 TRACE nova.openstack.common.threadgroup   File "/opt/stack/nova/nova/service.py", line 154, in start
2013-09-02 00:59:41.382 TRACE nova.openstack.common.threadgroup     self.manager.init_host()
2013-09-02 00:59:41.382 TRACE nova.openstack.common.threadgroup   File "/opt/stack/nova/nova/compute/manager.py", line 757, in init_host
2013-09-02 00:59:41.382 TRACE nova.openstack.common.threadgroup     self._report_driver_status(context)
2013-09-02 00:59:41.382 TRACE nova.openstack.common.threadgroup   File "/opt/stack/nova/nova/compute/manager.py", line 4409, in _report_driver_status
2013-09-02 00:59:41.382 TRACE nova.openstack.common.threadgroup     capabilities = self.driver.get_host_stats(refresh=True)
2013-09-02 00:59:41.382 TRACE nova.openstack.common.threadgroup   File "/opt/stack/nova/nova/virt/vmwareapi/driver.py", line 363, in get_host_stats
2013-09-02 00:59:41.382 TRACE nova.openstack.common.threadgroup     return self.host_state.get_host_stats(refresh=refresh)
2013-09-02 00:59:41.382 TRACE nova.openstack.common.threadgroup   File "/opt/stack/nova/nova/virt/vmwareapi/driver.py", line 434, in host_state
2013-09-02 00:59:41.382 TRACE nova.openstack.common.threadgroup     self._cluster)
2013-09-02 00:59:41.382 TRACE nova.openstack.common.threadgroup   File "/opt/stack/nova/nova/virt/vmwareapi/host.py", line 155, in __init__
2013-09-02 00:59:41.382 TRACE nova.openstack.common.threadgroup     self.update_status()
2013-09-02 00:59:41.382 TRACE nova.openstack.common.threadgroup   File "/opt/stack/nova/nova/virt/vmwareapi/host.py", line 201, in update_status
2013-09-02 00:59:41.382 TRACE nova.openstack.common.threadgroup     summary.quickStats.overallMemoryUsage
2013-09-02 00:59:41.382 TRACE nova.openstack.common.threadgroup AttributeError: 'Text' object has no attribute 'overallMemoryUsage'
2013-09-02 00:59:41.382 TRACE nova.openstack.common.threadgroup 
2013-09-02 00:59:41.385 DEBUG amqp [-] Closed channel #1 from (pid=27298) _do_close /usr/local/lib/python2.7/dist-packages/amqp/channel.py:88
nicira@os-devstack:/opt/stack/nova$