[19.04,Bionic] uds_comms never end (blocks config_changed_postupgrade)

[Alvaro Uria]

During the operation to upgrade from Queens to Rocky, and later from Rocky to Stein, I did the following step (action-managed-upgrade=true):
* juju config keystone openstack-origin=<TARGET>

after more than 40 minutes, hooks/config-changed was stuck and I had to kill it:
"""

unit-keystone-6: 21:57:02 DEBUG unit.keystone/6.config-changed /usr/lib/python3/dist-packages/keystoneauth1/adapter.py:200: UserWarning: Using keystoneclient sessions has been deprecated. Please update your software to use keystoneauth1.
unit-keystone-6: 21:57:02 DEBUG unit.keystone/6.config-changed warnings.warn('Using keystoneclient sessions has been deprecated. '
unit-keystone-6: 21:57:02 DEBUG unit.keystone/6.config-changed Traceback (most recent call last):
unit-keystone-6: 21:57:02 DEBUG unit.keystone/6.config-changed File "/var/lib/juju/agents/unit-keystone-6/charm/hooks/uds_comms.py", line 225, in send
unit-keystone-6: 21:57:02 DEBUG unit.keystone/6.config-changed self.sock.sendall(self.codec.encode(buffer))
unit-keystone-6: 21:57:02 DEBUG unit.keystone/6.config-changed BrokenPipeError: [Errno 32] Broken pipe
unit-keystone-6: 21:57:02 DEBUG unit.keystone/6.config-changed
unit-keystone-6: 21:57:02 DEBUG unit.keystone/6.config-changed During handling of the above exception, another exception occurred:
unit-keystone-6: 21:57:02 DEBUG unit.keystone/6.config-changed
unit-keystone-6: 21:57:02 DEBUG unit.keystone/6.config-changed Traceback (most recent call last):
unit-keystone-6: 21:57:02 DEBUG unit.keystone/6.config-changed File "/var/lib/juju/agents/unit-keystone-6/charm/hooks/manager.py", line 591, in <module>
unit-keystone-6: 21:57:02 DEBUG unit.keystone/6.config-changed uds_client.send(result_json)
unit-keystone-6: 21:57:02 DEBUG unit.keystone/6.config-changed File "/var/lib/juju/agents/unit-keystone-6/charm/hooks/uds_comms.py", line 227, in send
unit-keystone-6: 21:57:02 DEBUG unit.keystone/6.config-changed raise UDSException(str(e))
unit-keystone-6: 21:57:02 DEBUG unit.keystone/6.config-changed uds_comms.UDSException: [Errno 32] Broken pipe
unit-keystone-6: 21:57:06 ERROR juju.worker.uniter.operation hook "config-changed" failed: signal: terminated
"""

Later, when I ran the "openstack-upgrade" action, it happened again but this time, hooks/ config-changed-postupgrade was the script to be killed.

"socat UNIX-CONNECT:/tmp/keystone-uds -" doesn't show anything.

[Alex Kavanagh (ajkavanagh)]

There's insufficient information to identify the fault. Please add the log files (if they still exist). Otherwise, please re-open the bug if the issue is still arising. Otherwise the bug will time out in 60 days.

[Launchpad Janitor (janitor)]

[Expired for OpenStack keystone charm because there has been no activity for 60 days.]