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[Bug 1781286] Re: CantStartEngineError in cell conductor during reschedule - get_host_availability_zone up-call

 

Note for backports: this problem goes back to Pike but we won't be able
to backport the fix since it's going to require RPC API version changes.

** No longer affects: nova/pike

** No longer affects: nova/queens

** Changed in: nova
     Assignee: (unassigned) => Matt Riedemann (mriedem)

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https://bugs.launchpad.net/bugs/1781286

Title:
  CantStartEngineError in cell conductor during reschedule -
  get_host_availability_zone up-call

Status in OpenStack Compute (nova):
  Triaged

Bug description:
  In a stable/queens devstack environment with multiple PowerVM compute
  nodes, everytime I see this in devstack@n-cond-cell1.service logs:

  Jul 11 15:48:57 myhostname nova-conductor[3796]: DEBUG
  nova.conductor.manager [None req-af22375c-f920-4747-bd2f-0de80ee69465
  admin admin] Rescheduling: True {{(pid=4108) build_instances
  /opt/stack/nova/nova/conductor/manager.py:571}}

  it is shortly thereafter followed by:

  Jul 11 15:48:57 myhostname nova-conductor[3796]: ERROR oslo_messaging.rpc.server [None req-af22375c-f920-4747-bd2f-0de80ee69465 admin admin] Exception during message handling: CantStartEngineError: No sql_connection parameter is established
  Jul 11 15:48:57 myhostname nova-conductor[3796]: ERROR oslo_messaging.rpc.server Traceback (most recent call last):
  Jul 11 15:48:57 myhostname nova-conductor[3796]: ERROR oslo_messaging.rpc.server   File "/usr/local/lib/python2.7/dist-packages/oslo_messaging/rpc/server.py", line 163, in _process_incoming
  Jul 11 15:48:57 myhostname nova-conductor[3796]: ERROR oslo_messaging.rpc.server     res = self.dispatcher.dispatch(message)
  Jul 11 15:48:57 myhostname nova-conductor[3796]: ERROR oslo_messaging.rpc.server   File "/usr/local/lib/python2.7/dist-packages/oslo_messaging/rpc/dispatcher.py", line 220, in dispatch
  Jul 11 15:48:57 myhostname nova-conductor[3796]: ERROR oslo_messaging.rpc.server     return self._do_dispatch(endpoint, method, ctxt, args)
  Jul 11 15:48:57 myhostname nova-conductor[3796]: ERROR oslo_messaging.rpc.server   File "/usr/local/lib/python2.7/dist-packages/oslo_messaging/rpc/dispatcher.py", line 190, in _do_dispatch
  Jul 11 15:48:57 myhostname nova-conductor[3796]: ERROR oslo_messaging.rpc.server     result = func(ctxt, **new_args)
  Jul 11 15:48:57 myhostname nova-conductor[3796]: ERROR oslo_messaging.rpc.server   File "/opt/stack/nova/nova/conductor/manager.py", line 652, in build_instances
  Jul 11 15:48:57 myhostname nova-conductor[3796]: ERROR oslo_messaging.rpc.server     host.service_host))
  Jul 11 15:48:57 myhostname nova-conductor[3796]: ERROR oslo_messaging.rpc.server   File "/opt/stack/nova/nova/availability_zones.py", line 95, in get_host_availability_zone
  Jul 11 15:48:57 myhostname nova-conductor[3796]: ERROR oslo_messaging.rpc.server     key='availability_zone')
  Jul 11 15:48:57 myhostname nova-conductor[3796]: ERROR oslo_messaging.rpc.server   File "/usr/local/lib/python2.7/dist-packages/oslo_versionedobjects/base.py", line 184, in wrapper
  Jul 11 15:48:57 myhostname nova-conductor[3796]: ERROR oslo_messaging.rpc.server     result = fn(cls, context, *args, **kwargs)
  Jul 11 15:48:57 myhostname nova-conductor[3796]: ERROR oslo_messaging.rpc.server   File "/opt/stack/nova/nova/objects/aggregate.py", line 541, in get_by_host
  Jul 11 15:48:57 myhostname nova-conductor[3796]: ERROR oslo_messaging.rpc.server     _get_by_host_from_db(context, host, key=key)]
  Jul 11 15:48:57 myhostname nova-conductor[3796]: ERROR oslo_messaging.rpc.server   File "/usr/local/lib/python2.7/dist-packages/oslo_db/sqlalchemy/enginefacade.py", line 987, in wrapper
  Jul 11 15:48:57 myhostname nova-conductor[3796]: ERROR oslo_messaging.rpc.server     with self._transaction_scope(context):
  Jul 11 15:48:57 myhostname nova-conductor[3796]: ERROR oslo_messaging.rpc.server   File "/usr/lib/python2.7/contextlib.py", line 17, in __enter__
  Jul 11 15:48:57 myhostname nova-conductor[3796]: ERROR oslo_messaging.rpc.server     return self.gen.next()
  Jul 11 15:48:57 myhostname nova-conductor[3796]: ERROR oslo_messaging.rpc.server   File "/usr/local/lib/python2.7/dist-packages/oslo_db/sqlalchemy/enginefacade.py", line 1037, in _transaction_scope
  Jul 11 15:48:57 myhostname nova-conductor[3796]: ERROR oslo_messaging.rpc.server     context=context) as resource:
  Jul 11 15:48:57 myhostname nova-conductor[3796]: ERROR oslo_messaging.rpc.server   File "/usr/lib/python2.7/contextlib.py", line 17, in __enter__
  Jul 11 15:48:57 myhostname nova-conductor[3796]: ERROR oslo_messaging.rpc.server     return self.gen.next()
  Jul 11 15:48:57 myhostname nova-conductor[3796]: ERROR oslo_messaging.rpc.server   File "/usr/local/lib/python2.7/dist-packages/oslo_db/sqlalchemy/enginefacade.py", line 640, in _session
  Jul 11 15:48:57 myhostname nova-conductor[3796]: ERROR oslo_messaging.rpc.server     bind=self.connection, mode=self.mode)
  Jul 11 15:48:57 myhostname nova-conductor[3796]: ERROR oslo_messaging.rpc.server   File "/usr/local/lib/python2.7/dist-packages/oslo_db/sqlalchemy/enginefacade.py", line 404, in _create_session
  Jul 11 15:48:57 myhostname nova-conductor[3796]: ERROR oslo_messaging.rpc.server     self._start()
  Jul 11 15:48:57 myhostname nova-conductor[3796]: ERROR oslo_messaging.rpc.server   File "/usr/local/lib/python2.7/dist-packages/oslo_db/sqlalchemy/enginefacade.py", line 491, in _start
  Jul 11 15:48:57 myhostname nova-conductor[3796]: ERROR oslo_messaging.rpc.server     engine_args, maker_args)
  Jul 11 15:48:57 myhostname nova-conductor[3796]: ERROR oslo_messaging.rpc.server   File "/usr/local/lib/python2.7/dist-packages/oslo_db/sqlalchemy/enginefacade.py", line 513, in _setup_for_connection
  Jul 11 15:48:57 myhostname nova-conductor[3796]: ERROR oslo_messaging.rpc.server     "No sql_connection parameter is established")
  Jul 11 15:48:57 myhostname nova-conductor[3796]: ERROR oslo_messaging.rpc.server CantStartEngineError: No sql_connection parameter is established
  Jul 11 15:48:57 myhostname nova-conductor[3796]: ERROR oslo_messaging.rpc.server

  The nova_cell1.conf does have [database]connection set:

  [database]
  connection = mysql+pymysql://root:mysql@127.0.0.1/nova_cell1?charset=utf8

  This may be related to https://bugs.launchpad.net/nova/+bug/1736946 ,
  though that is supposedly fixed in stable/queens and the trace is
  different, hence the new defect.

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References