interface attach with QoS port fails with "cannot unpack non-iterable NoneType object" if Placement is down

[Balazs Gibizer]

The interface attach code does not handle if placement is down while nova try to queries allocation candidates from placement. The safe_connect decorator on the report client method returns None when placement is not available but the manager code tries to unpack the return value to a 3 tuple[1].

        res = self.reportclient.get_allocation_candidates(context, rr)
        alloc_reqs, provider_sums, version = res

This leads to a TypeError and HTTP 500 response code.

2021-08-07 09:59:28,967 WARNING [nova.scheduler.client.report] Placement API service is not responding.
2021-08-07 09:59:29,130 ERROR [oslo_messaging.rpc.server] Exception during message handling
Traceback (most rece
    nt call last):
  File "/root/rtox/nova/functional-py38/.tox/functional-py38/lib/python3.8/site-packages/oslo_messaging/rpc/server.py", line 165, in _process_incoming
    res = self.dispatcher.dispatch(message)
  File "/root/rtox/nova/functional-py38/.tox/functional-py38/lib/python3.8/site-packages/oslo_messaging/rpc/dispatcher.py", line 309, in dispatch
    return self._do_dispatch(endpoint, method, ctxt, args)
  File "/root/rtox/nova/functional-py38/.tox/functional-py38/lib/python3.8/site-packages/oslo_messaging/rpc/dispatcher.py", line 229, in _do_dispatch
    result = func(ctxt, **new_args)
  File "/root/rtox/nova/functional-py38/.tox/functional-py38/lib/python3.8/site-packages/oslo_messaging/rpc/server.py", line 241, in inner
    return func(*args, **kwargs)
  File "/root/rtox/nova/functional-py38/nova/exception_wrapper.py", line 71, in wrapped
    _emit_versioned_exception_notification(
  File "/root/rtox/nova/functional-py38/.tox/functional-py38/lib/python3.8/site-packages/oslo_utils/excutils.py", line 227, in __exit__
    self.force_reraise()
  File "/root/rtox/nova/functional-py38/.tox/functional-py38/lib/python3.8/site-packages/oslo_utils/excutils.py", line 200, in force_reraise
    raise self.value
  File "/root/rtox/nova/functional-py38/nova/exception_wrapper.py", line 63, in wrapped
    return f(self, context, *args, **kw)
  File "/root/rtox/nova/functional-py38/nova/compute/utils.py", line 1433, in decorated_function
    return function(self, context, *args, **kwargs)
  File "/root/rtox/nova/functional-py38/nova/compute/manager.py", line 211, in decorated_function
    compute_utils.add_instance_fault_from_exc(context,
  File "/root/rtox/nova/functional-py38/.tox/functional-py38/lib/python3.8/site-packages/oslo_utils/excutils.py", line 227, in __exit__
    self.force_reraise()
  File "/root/rtox/nova/functional-py38/.tox/functional-py38/lib/python3.8/site-packages/oslo_utils/excutils.py", line 200, in force_reraise
    raise self.value
  File "/root/rtox/nova/functional-py38/nova/compute/manager.py", line 200, in decorated_function
    return function(self, context, *args, **kwargs)
  File "/root/rtox/nova/functional-py38/nova/compute/manager.py", line 7735, in attach_interface
    return do_attach_interface(context, instance, network_id, port_id,
  File "/root/rtox/nova/functional-py38/.tox/functional-py38/lib/python3.8/site-packages/oslo_concurrency/lockutils.py", line 360, in inner
    return f(*args, **kwargs)
  File "/root/rtox/nova/functional-py38/nova/compute/manager.py", line 7732, in do_attach_interface
    return self._attach_interface(context, instance, network_id,
  File "/root/rtox/nova/functional-py38/nova/compute/manager.py", line 7787, in _attach_interface
    result = self._allocate_port_resource_for_instance(
  File "/root/rtox/nova/functional-py38/nova/compute/manager.py", line 7656, in _allocate_port_resource_for_instance
    alloc_reqs, provider_sums, version = res
TypeError: cannot unpack non-iterable NoneType object
2021-08-07 09:59:29,131 ERROR [nova.api.openstack.wsgi] Unexpected exception in API method
Traceback (most recent call last):
  File "/root/rtox/nova/functional-py38/.tox/functional-py38/lib/python3.8/site-packages/urllib3/connectionpool.py", line 436, in _make_request
    httplib_response = conn.getresponse(buffering=True)
TypeError: getresponse() got an unexpected keyword argument 'buffering'

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/root/rtox/nova/functional-py38/nova/api/openstack/wsgi.py", line 658, in wrapped
    return f(*args, **kwargs)
  File "/root/rtox/nova/functional-py38/nova/api/validation/__init__.py", line 110, in wrapper
    return func(*args, **kwargs)
  File "/root/rtox/nova/functional-py38/nova/api/validation/__init__.py", line 110, in wrapper
    return func(*args, **kwargs)
  File "/root/rtox/nova/functional-py38/nova/api/openstack/compute/attach_interfaces.py", line 168, in create
    vif = self.compute_api.attach_interface(context,
  File "/root/rtox/nova/functional-py38/nova/comp
    ute/api.py", line 226, in inner
    return function(self, context, instance, *args, **kwargs)
  File "/root/rtox/nova/functional-py38/nova/compute/api.py", line 153, in inner
    return f(self, context, instance, *args, **kw)
  File "/root/rtox/nova/functional-py38/nova/compute/api.py", line 5046, in attach_interface
    return self.compute_rpcapi.attach_interface(context,
  File "/root/rtox/nova/functional-py38/nova/compute/rpcapi.py", line 570, in attach_interface
    return cctxt.call(ctxt, 'attach_interface', **kw)
  File "/root/rtox/nova/functional-py38/.tox/functional-py38/lib/python3.8/site-packages/oslo_messaging/rpc/client.py", line 175, in call
    self.transport._send(self.target, msg_ctxt, msg,
  File "/root/rtox/nova/functional-py38/.tox/functional-py38/lib/python3.8/site-packages/oslo_messaging/transport.py", line 123, in _send
    return self._driver.send(target, ctxt, message,
  File "/root/rtox/nova/functional-py38/.tox/functional-py38/lib/python3.8/site-packages/oslo_messaging/_drivers/impl_fake.py", line 222, in send
    return self._send(target, ctxt, message, wait_for_reply, timeout,
  File "/root/rtox/nova/functional-py38/.tox/functional-py38/lib/python3.8/site-packages/oslo_messaging/_drivers/impl_fake.py", line 209, in _send
    raise failure
  File "/root/rtox/nova/functional-py38/.tox/functional-py38/lib/python3.8/site-packages/oslo_messaging/rpc/server.py", line 165, in _process_incoming
    res = self.dispatcher.dispatch(message)
  File "/root/rtox/nova/functional-py38/.tox/functional-py38/lib/python3.8/site-packages/oslo_messaging/rpc/dispatcher.py", line 309, in dispatch
    return self._do_dispatch(endpoint, method, ctxt, args)
  File "/root/rtox/nova/functional-py38/.tox/functional-py38/lib/python3.8/site-packages/oslo_messaging/rpc/dispatcher.py", line 229, in _do_dispatch
    result = func(ctxt, **new_args)
  File "/root/rtox/nova/functional-py38/.tox/functional-py38/lib/python3.8/site-packages/oslo_messaging/rpc/server.py", line 241, in inner
    return func(*args, **kwargs)
  File "/root/rtox/nova/functional-py38/nova/exception_wrapper.py", line 71, in wrapped
    _emit_versioned_exception_notification(
  File "/root/rtox/nova/functional-py38/.tox/functional-py38/lib/python3.8/site-packages/oslo_utils/excutils.py", line 227, in __exit__
    self.force_reraise()
  File "/root/rtox/nova/functional-py38/.tox/functional-py38/lib/python3.8/site-packages/oslo_utils/excutils.py", line 200, in force_reraise
    raise self.value
  File "/root/rtox/nova/functional-py38/nova/exception_wrapper.py", line 63, in wrapped
    return f(self, context, *args, **kw)
  File "/root/rtox/nova/functional-py38/nova/compute/utils.py", line 1433, in decorated_function
    return function(self, context, *args, **kwargs)
  File "/root/rtox/nova/functional-py38/nova/compute/manager.py", line 211, in decorated_function
    compute_utils.add_instance_fault_from_exc(context,
  File "/root/rtox/nova/functional-py38/.tox/functional-py38/lib/python3.8/site-packages/oslo_utils/excutils.py", line 227, in __exit__
    self.force_reraise()
  File "/root/rtox/nova/functional-py38/.tox/functional-py38/lib/python3.8/site-packages/oslo_utils/excutils.py", line 200, in force_reraise
    raise self.value
  File "/root/rtox/nova/functional-py38/nova/compute/manager.py", line 200, in decorated_function
    return function(self, context, *args, **kwargs)
  File "/root/rtox/nova/functional-py38/nova/compute/manager.py", line 7735, in attach_interface
    return do_attach_interface(context, instance, network_id, port_id,
  File "/root/rtox/nova/functional-py38/.tox/functional-py38/lib/python3.8/site-packages/oslo_concurrency/lockutils.py", line 360, in inner
    return f(*args, **kwargs)
  File "/root/rtox/nova/functional-py38/nova/compute/manager.py", line 7732, in do_attach_interface
    return self._attach_interface(context, instance, network_id,
  File "/root/rtox/nova/functional-py38/nova/compute/manager.py", line 7787, in _attach_interface
    result = self._allocate_port_resource_for_instance(
  File "/root/rtox/nova/functional-
    py38/nova/compute/manager.py", line 7656, in _allocate_port_resource_for_instance
    alloc_reqs, provider_sums, version = res
TypeError: cannot unpack non-iterable NoneType object
2021-08-07 09:59:29,133 INFO [nova.api.openstack.wsgi] HTTP exception thrown: Unexpected API Error. Please report this at http://bugs.launchpad.net/nova/ and attach the Nova API log if possible.
<class 'TypeError'>

[1] https://github.com/openstack/nova/blob/99536b95bcc4c1dd09099abd858233c9352afeed/nova/compute/manager.py#L7646

[Balazs Gibizer (balazs-gibizer)]

This bug is there since the QoS interface attach support added in Wallaby[1]

[1] Id4684093e8bdf3b61667490443e3d2f6ed65f4b3

[OpenStack Infra (hudson-openstack)]

Related fix proposed to branch: master
Review: https://review.opendev.org/c/openstack/nova/+/803821

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.opendev.org/c/openstack/nova/+/803822