Hi!

We are experiencing high latencies from time to time in one of our
openstack environments.  While looking into the issue we found that
the southdb has frequent leader changes.

We are running the Xena release and ovsdb-server (Open vSwitch) 2.16.0
deployed via kolla-ansible.

--- cut ---
2022-04-07T06:51:41.782Z|00952|raft|INFO|received leadership transfer
from 3da8 in term 7545
2022-04-07T07:10:27.993Z|00925|raft|INFO|received leadership transfer
from 1c5f in term 7546
2022-04-07T07:10:53.355Z|01061|raft|INFO|received leadership transfer
from f177 in term 7547
2022-04-07T07:28:09.193Z|00938|raft|INFO|received leadership transfer
from 1c5f in term 7548
2022-04-07T07:43:24.377Z|01166|raft|INFO|received leadership transfer
from f177 in term 7549
2022-04-07T07:44:01.979Z|01031|raft|INFO|received leadership transfer
from 1c5f in term 7550
2022-04-07T08:02:17.876Z|01179|raft|INFO|received leadership transfer
from f177 in term 7551
2022-04-07T08:15:21.329Z|01137|raft|INFO|received leadership transfer
from 1c5f in term 7552
2022-04-07T08:32:54.440Z|01262|raft|INFO|received leadership transfer
from f177 in term 7553
2022-04-07T08:34:05.864Z|01248|raft|INFO|received leadership transfer
from 1c5f in term 7554
2022-04-07T08:47:48.497Z|01279|raft|INFO|received leadership transfer
from f177 in term 7555
2022-04-07T08:48:12.508Z|01333|raft|INFO|received leadership transfer
from 1c5f in term 7556
2022-04-07T09:03:08.086Z|01286|raft|INFO|received leadership transfer
from f177 in term 7557
2022-04-07T09:03:27.895Z|01428|raft|INFO|received leadership transfer
from 1c5f in term 7558
2022-04-07T09:16:34.045Z|01291|raft|INFO|received leadership transfer
from f177 in term 7559
2022-04-07T09:25:54.219Z|01512|raft|INFO|received leadership transfer
from 1c5f in term 7560
2022-04-07T09:32:59.026Z|01348|raft|INFO|received leadership transfer
from f177 in term 7561
2022-04-07T09:42:53.125Z|01556|raft|INFO|received leadership transfer
from 1c5f in term 7562
2022-04-07T09:46:42.450Z|01414|raft|INFO|received leadership transfer
from f177 in term 7563
2022-04-07T09:54:20.665Z|01582|raft|INFO|received leadership transfer
from 1c5f in term 7564
2022-04-07T09:58:28.906Z|01458|raft|INFO|received leadership transfer
from f177 in term 7565
2022-04-07T10:09:09.271Z|01610|raft|INFO|received leadership transfer
from 1c5f in term 7566
2022-04-07T10:26:56.792Z|01528|raft|INFO|received leadership transfer
from f177 in term 7567
2022-04-07T10:27:34.885Z|01716|raft|INFO|received leadership transfer
from 1c5f in term 7568
2022-04-07T10:41:38.178Z|01533|raft|INFO|received leadership transfer
from f177 in term 7569
2022-04-07T10:42:25.543Z|01807|raft|INFO|received leadership transfer
from 1c5f in term 7570
2022-04-07T10:55:46.772Z|01540|raft|INFO|received leadership transfer
from f177 in term 7571
2022-04-07T11:00:55.610Z|01892|raft|INFO|received leadership transfer
from 1c5f in term 7572
2022-04-07T11:14:17.057Z|01575|raft|INFO|received leadership transfer
from f177 in term 7573
2022-04-07T11:26:58.164Z|01971|raft|INFO|received leadership transfer
from 1c5f in term 7574
2022-04-07T11:43:44.300Z|01657|raft|INFO|received leadership transfer
from f177 in term 7575
2022-04-07T11:53:17.514Z|02075|raft|INFO|received leadership transfer
from 1c5f in term 7576
2022-04-07T11:59:42.938Z|01714|raft|INFO|received leadership transfer
from f177 in term 7577
2022-04-07T12:07:32.316Z|02121|raft|INFO|received leadership transfer
from 1c5f in term 7578
2022-04-07T12:18:19.280Z|01765|raft|INFO|received leadership transfer
from f177 in term 7579
2022-04-07T12:22:57.588Z|02186|raft|INFO|received leadership transfer
from 1c5f in term 7580
2022-04-07T12:30:09.755Z|01799|raft|INFO|received leadership transfer
from f177 in term 7581
2022-04-07T12:36:53.283Z|02233|raft|INFO|received leadership transfer
from 1c5f in term 7582
2022-04-07T12:44:09.022Z|01846|raft|INFO|received leadership transfer
from f177 in term 7583
2022-04-07T12:47:16.956Z|02278|raft|INFO|received leadership transfer
from 1c5f in term 7584
2022-04-07T12:54:14.197Z|01870|raft|INFO|received leadership transfer
from f177 in term 7585
--- cut ---

We also noticed that the leader changes are caused by snapshots
(database compaction?).

--- cut ---
2022-04-07T07:10:27.993Z|01057|raft|INFO|Transferring leadership to
write a snapshot.
2022-04-07T07:28:09.193Z|01162|raft|INFO|Transferring leadership to
write a snapshot.
2022-04-07T07:44:01.979Z|01175|raft|INFO|Transferring leadership to
write a snapshot.
2022-04-07T08:15:21.329Z|01258|raft|INFO|Transferring leadership to
write a snapshot.
2022-04-07T08:34:05.863Z|01275|raft|INFO|Transferring leadership to
write a snapshot.
2022-04-07T08:48:12.508Z|01282|raft|INFO|Transferring leadership to
write a snapshot.
2022-04-07T09:03:27.894Z|01289|raft|INFO|Transferring leadership to
write a snapshot.
2022-04-07T09:25:54.219Z|01344|raft|INFO|Transferring leadership to
write a snapshot.
2022-04-07T09:42:53.125Z|01410|raft|INFO|Transferring leadership to
write a snapshot.
2022-04-07T09:54:20.665Z|01454|raft|INFO|Transferring leadership to
write a snapshot.
2022-04-07T10:09:09.270Z|01524|raft|INFO|Transferring leadership to
write a snapshot.
2022-04-07T10:27:34.884Z|01531|raft|INFO|Transferring leadership to
write a snapshot.
2022-04-07T10:42:25.543Z|01536|raft|INFO|Transferring leadership to
write a snapshot.
2022-04-07T11:00:55.610Z|01571|raft|INFO|Transferring leadership to
write a snapshot.
2022-04-07T11:26:58.164Z|01653|raft|INFO|Transferring leadership to
write a snapshot.
2022-04-07T11:53:17.514Z|01710|raft|INFO|Transferring leadership to
write a snapshot.
2022-04-07T12:07:32.316Z|01759|raft|INFO|Transferring leadership to
write a snapshot.
2022-04-07T12:22:57.588Z|01795|raft|INFO|Transferring leadership to
write a snapshot.
2022-04-07T12:36:53.282Z|01842|raft|INFO|Transferring leadership to
write a snapshot.
--- cut ---

Do these changes/snapshots have an impact on the performance of the southdb?

Is there anything to improve the performance in case of leadership changes?

Kind regards,

Christian Stelter
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