Paste-bins expire, so copy/pasting content from the paste-bin (http://paste.openstack.org/show/798201/) in the description below:

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2020-09-21 11:12:27.538 3887 INFO nova.compute.manager [req-1363655f-fa54-4674-a5ae-d1d26d2ea86d 473593595cf04e41a6382d261eea3576 19151bb269ae4214bdf83e18083e8b54 - default default] [instance: cd879458-57d9-4f4c-8214-1f99456b6f42] Swapping volume ed93fa66-13d0-447e-8084-4fd523cf3015 for 1bde1669-657e-4608-a8c6-b654ef58121f
2020-09-21 11:12:28.979 3887 INFO os_brick.initiator.connectors.iscsi [req-1363655f-fa54-4674-a5ae-d1d26d2ea86d 473593595cf04e41a6382d261eea3576 19151bb269ae4214bdf83e18083e8b54 - default default] Trying to connect to iSCSI portal 172.20.213.204:3260
2020-09-21 11:13:56.292 3887 ERROR nova.compute.manager [req-1363655f-fa54-4674-a5ae-d1d26d2ea86d 473593595cf04e41a6382d261eea3576 19151bb269ae4214bdf83e18083e8b54 - default default] [instance: cd879458-57d9-4f4c-8214-1f99456b6f42] Failed to swap volume ed93fa66-13d0-447e-8084-4fd523cf3015 for 1bde1669-657e-4608-a8c6-b654ef58121f: libvirtError: block copy still active: domain has active block job
2020-09-21 11:13:56.292 3887 ERROR nova.compute.manager [instance: cd879458-57d9-4f4c-8214-1f99456b6f42] Traceback (most recent call last):
2020-09-21 11:13:56.292 3887 ERROR nova.compute.manager [instance: cd879458-57d9-4f4c-8214-1f99456b6f42]   File "/openstack/venvs/nova-18.1.5/lib/python2.7/site-packages/nova/compute/manager.py", line 5726, in _swap_volume
2020-09-21 11:13:56.292 3887 ERROR nova.compute.manager [instance: cd879458-57d9-4f4c-8214-1f99456b6f42]     mountpoint, resize_to)
2020-09-21 11:13:56.292 3887 ERROR nova.compute.manager [instance: cd879458-57d9-4f4c-8214-1f99456b6f42]   File "/openstack/venvs/nova-18.1.5/lib/python2.7/site-packages/nova/virt/libvirt/driver.py", line 1568, in swap_volume
2020-09-21 11:13:56.292 3887 ERROR nova.compute.manager [instance: cd879458-57d9-4f4c-8214-1f99456b6f42]     self._swap_volume(guest, disk_dev, conf, resize_to)
2020-09-21 11:13:56.292 3887 ERROR nova.compute.manager [instance: cd879458-57d9-4f4c-8214-1f99456b6f42]   File "/openstack/venvs/nova-18.1.5/lib/python2.7/site-packages/nova/virt/libvirt/driver.py", line 1530, in _swap_volume
2020-09-21 11:13:56.292 3887 ERROR nova.compute.manager [instance: cd879458-57d9-4f4c-8214-1f99456b6f42]     self._host.write_instance_config(xml)
2020-09-21 11:13:56.292 3887 ERROR nova.compute.manager [instance: cd879458-57d9-4f4c-8214-1f99456b6f42]   File "/openstack/venvs/nova-18.1.5/lib/python2.7/site-packages/nova/virt/libvirt/host.py", line 864, in write_instance_config
2020-09-21 11:13:56.292 3887 ERROR nova.compute.manager [instance: cd879458-57d9-4f4c-8214-1f99456b6f42]     domain = self.get_connection().defineXML(xml)
2020-09-21 11:13:56.292 3887 ERROR nova.compute.manager [instance: cd879458-57d9-4f4c-8214-1f99456b6f42]   File "/openstack/venvs/nova-18.1.5/lib/python2.7/site-packages/eventlet/tpool.py", line 186, in doit
2020-09-21 11:13:56.292 3887 ERROR nova.compute.manager [instance: cd879458-57d9-4f4c-8214-1f99456b6f42]     result = proxy_call(self._autowrap, f, *args, **kwargs)
2020-09-21 11:13:56.292 3887 ERROR nova.compute.manager [instance: cd879458-57d9-4f4c-8214-1f99456b6f42]   File "/openstack/venvs/nova-18.1.5/lib/python2.7/site-packages/eventlet/tpool.py", line 144, in proxy_call
2020-09-21 11:13:56.292 3887 ERROR nova.compute.manager [instance: cd879458-57d9-4f4c-8214-1f99456b6f42]     rv = execute(f, *args, **kwargs)
2020-09-21 11:13:56.292 3887 ERROR nova.compute.manager [instance: cd879458-57d9-4f4c-8214-1f99456b6f42]   File "/openstack/venvs/nova-18.1.5/lib/python2.7/site-packages/eventlet/tpool.py", line 125, in execute
2020-09-21 11:13:56.292 3887 ERROR nova.compute.manager [instance: cd879458-57d9-4f4c-8214-1f99456b6f42]     six.reraise(c, e, tb)
2020-09-21 11:13:56.292 3887 ERROR nova.compute.manager [instance: cd879458-57d9-4f4c-8214-1f99456b6f42]   File "/openstack/venvs/nova-18.1.5/lib/python2.7/site-packages/eventlet/tpool.py", line 83, in tworker
2020-09-21 11:13:56.292 3887 ERROR nova.compute.manager [instance: cd879458-57d9-4f4c-8214-1f99456b6f42]     rv = meth(*args, **kwargs)
2020-09-21 11:13:56.292 3887 ERROR nova.compute.manager [instance: cd879458-57d9-4f4c-8214-1f99456b6f42]   File "/openstack/venvs/nova-18.1.5/lib/python2.7/site-packages/libvirt.py", line 3621, in defineXML
2020-09-21 11:13:56.292 3887 ERROR nova.compute.manager [instance: cd879458-57d9-4f4c-8214-1f99456b6f42]     if ret is None:raise libvirtError('virDomainDefineXML() failed', conn=self)
2020-09-21 11:13:56.292 3887 ERROR nova.compute.manager [instance: cd879458-57d9-4f4c-8214-1f99456b6f42] libvirtError: block copy still active: domain has active block job
2020-09-21 11:13:56.292 3887 ERROR nova.compute.manager [instance: cd879458-57d9-4f4c-8214-1f99456b6f42]
2020-09-21 11:13:59.930 3887 ERROR oslo_messaging.rpc.server [req-1363655f-fa54-4674-a5ae-d1d26d2ea86d 473593595cf04e41a6382d261eea3576 19151bb269ae4214bdf83e18083e8b54 - default default] Exception during message handling: libvirtError: block copy still active: domain has active block job
2020-09-21 11:13:59.930 3887 ERROR oslo_messaging.rpc.server Traceback (most recent call last):
2020-09-21 11:13:59.930 3887 ERROR oslo_messaging.rpc.server   File "/openstack/venvs/nova-18.1.5/lib/python2.7/site-packages/oslo_messaging/rpc/server.py", line 163, in _process_incoming
2020-09-21 11:13:59.930 3887 ERROR oslo_messaging.rpc.server     res = self.dispatcher.dispatch(message)
2020-09-21 11:13:59.930 3887 ERROR oslo_messaging.rpc.server   File "/openstack/venvs/nova-18.1.5/lib/python2.7/site-packages/oslo_messaging/rpc/dispatcher.py", line 265, in dispatch
2020-09-21 11:13:59.930 3887 ERROR oslo_messaging.rpc.server     return self._do_dispatch(endpoint, method, ctxt, args)
2020-09-21 11:13:59.930 3887 ERROR oslo_messaging.rpc.server   File "/openstack/venvs/nova-18.1.5/lib/python2.7/site-packages/oslo_messaging/rpc/dispatcher.py", line 194, in _do_dispatch
2020-09-21 11:13:59.930 3887 ERROR oslo_messaging.rpc.server     result = func(ctxt, **new_args)
2020-09-21 11:13:59.930 3887 ERROR oslo_messaging.rpc.server   File "/openstack/venvs/nova-18.1.5/lib/python2.7/site-packages/nova/exception_wrapper.py", line 79, in wrapped
2020-09-21 11:13:59.930 3887 ERROR oslo_messaging.rpc.server     function_name, call_dict, binary, tb)
2020-09-21 11:13:59.930 3887 ERROR oslo_messaging.rpc.server   File "/openstack/venvs/nova-18.1.5/lib/python2.7/site-packages/oslo_utils/excutils.py", line 220, in __exit__
2020-09-21 11:13:59.930 3887 ERROR oslo_messaging.rpc.server     self.force_reraise()
2020-09-21 11:13:59.930 3887 ERROR oslo_messaging.rpc.server   File "/openstack/venvs/nova-18.1.5/lib/python2.7/site-packages/oslo_utils/excutils.py", line 196, in force_reraise
2020-09-21 11:13:59.930 3887 ERROR oslo_messaging.rpc.server     six.reraise(self.type_, self.value, self.tb)
2020-09-21 11:13:59.930 3887 ERROR oslo_messaging.rpc.server   File "/openstack/venvs/nova-18.1.5/lib/python2.7/site-packages/nova/exception_wrapper.py", line 69, in wrapped
2020-09-21 11:13:59.930 3887 ERROR oslo_messaging.rpc.server     return f(self, context, *args, **kw)
2020-09-21 11:13:59.930 3887 ERROR oslo_messaging.rpc.server   File "/openstack/venvs/nova-18.1.5/lib/python2.7/site-packages/nova/compute/utils.py", line 1141, in decorated_function
2020-09-21 11:13:59.930 3887 ERROR oslo_messaging.rpc.server     return function(self, context, *args, **kwargs)
2020-09-21 11:13:59.930 3887 ERROR oslo_messaging.rpc.server   File "/openstack/venvs/nova-18.1.5/lib/python2.7/site-packages/nova/compute/manager.py", line 216, in decorated_function
2020-09-21 11:13:59.930 3887 ERROR oslo_messaging.rpc.server     kwargs['instance'], e, sys.exc_info())
2020-09-21 11:13:59.930 3887 ERROR oslo_messaging.rpc.server   File "/openstack/venvs/nova-18.1.5/lib/python2.7/site-packages/oslo_utils/excutils.py", line 220, in __exit__
2020-09-21 11:13:59.930 3887 ERROR oslo_messaging.rpc.server     self.force_reraise()
2020-09-21 11:13:59.930 3887 ERROR oslo_messaging.rpc.server   File "/openstack/venvs/nova-18.1.5/lib/python2.7/site-packages/oslo_utils/excutils.py", line 196, in force_reraise
2020-09-21 11:13:59.930 3887 ERROR oslo_messaging.rpc.server     six.reraise(self.type_, self.value, self.tb)
2020-09-21 11:13:59.930 3887 ERROR oslo_messaging.rpc.server   File "/openstack/venvs/nova-18.1.5/lib/python2.7/site-packages/nova/compute/manager.py", line 204, in decorated_function
2020-09-21 11:13:59.930 3887 ERROR oslo_messaging.rpc.server     return function(self, context, *args, **kwargs)
2020-09-21 11:13:59.930 3887 ERROR oslo_messaging.rpc.server   File "/openstack/venvs/nova-18.1.5/lib/python2.7/site-packages/nova/compute/manager.py", line 5871, in swap_volume
2020-09-21 11:13:59.930 3887 ERROR oslo_messaging.rpc.server     is_cinder_migration)
2020-09-21 11:13:59.930 3887 ERROR oslo_messaging.rpc.server   File "/openstack/venvs/nova-18.1.5/lib/python2.7/site-packages/nova/compute/manager.py", line 5769, in _swap_volume
2020-09-21 11:13:59.930 3887 ERROR oslo_messaging.rpc.server     context, new_attachment_id)
2020-09-21 11:13:59.930 3887 ERROR oslo_messaging.rpc.server   File "/openstack/venvs/nova-18.1.5/lib/python2.7/site-packages/oslo_utils/excutils.py", line 220, in __exit__
2020-09-21 11:13:59.930 3887 ERROR oslo_messaging.rpc.server     self.force_reraise()
2020-09-21 11:13:59.930 3887 ERROR oslo_messaging.rpc.server   File "/openstack/venvs/nova-18.1.5/lib/python2.7/site-packages/oslo_utils/excutils.py", line 196, in force_reraise
2020-09-21 11:13:59.930 3887 ERROR oslo_messaging.rpc.server     six.reraise(self.type_, self.value, self.tb)
2020-09-21 11:13:59.930 3887 ERROR oslo_messaging.rpc.server   File "/openstack/venvs/nova-18.1.5/lib/python2.7/site-packages/nova/compute/manager.py", line 5726, in _swap_volume
2020-09-21 11:13:59.930 3887 ERROR oslo_messaging.rpc.server     mountpoint, resize_to)
2020-09-21 11:13:59.930 3887 ERROR oslo_messaging.rpc.server   File "/openstack/venvs/nova-18.1.5/lib/python2.7/site-packages/nova/virt/libvirt/driver.py", line 1568, in swap_volume
2020-09-21 11:13:59.930 3887 ERROR oslo_messaging.rpc.server     self._swap_volume(guest, disk_dev, conf, resize_to)
2020-09-21 11:13:59.930 3887 ERROR oslo_messaging.rpc.server   File "/openstack/venvs/nova-18.1.5/lib/python2.7/site-packages/nova/virt/libvirt/driver.py", line 1530, in _swap_volume
2020-09-21 11:13:59.930 3887 ERROR oslo_messaging.rpc.server     self._host.write_instance_config(xml)
2020-09-21 11:13:59.930 3887 ERROR oslo_messaging.rpc.server   File "/openstack/venvs/nova-18.1.5/lib/python2.7/site-packages/nova/virt/libvirt/host.py", line 864, in write_instance_config
2020-09-21 11:13:59.930 3887 ERROR oslo_messaging.rpc.server     domain = self.get_connection().defineXML(xml)
2020-09-21 11:13:59.930 3887 ERROR oslo_messaging.rpc.server   File "/openstack/venvs/nova-18.1.5/lib/python2.7/site-packages/eventlet/tpool.py", line 186, in doit
2020-09-21 11:13:59.930 3887 ERROR oslo_messaging.rpc.server     result = proxy_call(self._autowrap, f, *args, **kwargs)
2020-09-21 11:13:59.930 3887 ERROR oslo_messaging.rpc.server   File "/openstack/venvs/nova-18.1.5/lib/python2.7/site-packages/eventlet/tpool.py", line 144, in proxy_call
2020-09-21 11:13:59.930 3887 ERROR oslo_messaging.rpc.server     rv = execute(f, *args, **kwargs)
2020-09-21 11:13:59.930 3887 ERROR oslo_messaging.rpc.server   File "/openstack/venvs/nova-18.1.5/lib/python2.7/site-packages/eventlet/tpool.py", line 125, in execute
2020-09-21 11:13:59.930 3887 ERROR oslo_messaging.rpc.server     six.reraise(c, e, tb)
2020-09-21 11:13:59.930 3887 ERROR oslo_messaging.rpc.server   File "/openstack/venvs/nova-18.1.5/lib/python2.7/site-packages/eventlet/tpool.py", line 83, in tworker
2020-09-21 11:13:59.930 3887 ERROR oslo_messaging.rpc.server     rv = meth(*args, **kwargs)
2020-09-21 11:13:59.930 3887 ERROR oslo_messaging.rpc.server   File "/openstack/venvs/nova-18.1.5/lib/python2.7/site-packages/libvirt.py", line 3621, in defineXML
2020-09-21 11:13:59.930 3887 ERROR oslo_messaging.rpc.server     if ret is None:raise libvirtError('virDomainDefineXML() failed', conn=self)
2020-09-21 11:13:59.930 3887 ERROR oslo_messaging.rpc.server libvirtError: block copy still active: domain has active block job
2020-09-21 11:13:59.930 3887 ERROR oslo_messaging.rpc.server
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(That said, as discussed on IRC, for debugging libvirt/QEMU interactions, you might want to refer to:
https://kashyapc.fedorapeople.org/virt/openstack/request-nova-libvirt-qemu-debug-logs.txt)

But I see that Lee has got a handle on the 'nova-compute' side of things.