During an upgrade, nova pins the version of RPC calls to the minimum
seen across all services. This ensures that old services do not receive
data they cannot handle. After the upgrade is complete, all nova
services are supposed to be reloaded via SIGHUP to cause them to check
again the RPC versions of services and use the new latest version which
should now be supported by all running services.
Due to a bug [1] in oslo.service, sending services SIGHUP is currently
broken. We replaced the HUP with a restart for the nova_compute
container for bug 1821362, but not other nova services. It seems we need
to restart all nova services to allow the RPC version pin to be removed.
Testing in a Queens to Rocky upgrade, we find the following in the logs:
Automatically selected compute RPC version 5.0 from minimum service
version 30
However, the service version in Rocky is 35.
There is a second issue in that it takes some time for the upgraded
services to update the nova services database table with their new
version. We need to wait until all nova-compute services have done this
before the restart is performed, otherwise the RPC version cap will
remain in place. There is currently no interface in nova available for
checking these versions [2], so as a workaround we use a configurable
delay with a default duration of 30 seconds. Testing showed it takes
about 10 seconds for the version to be updated, so this gives us some
headroom.
This change restarts all nova services after an upgrade, after a 30
second delay.
[1] https://bugs.launchpad.net/oslo.service/+bug/1715374
[2] https://bugs.launchpad.net/nova/+bug/1833542
Change-Id: Ia6fc9011ee6f5461f40a1307b72709d769814a79
Closes-Bug: #1833069
Related-Bug: #1833542
(cherry picked from commit e6d2b92200)
96a96a2655