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Switchover s6 master (db1173 -> db1131)
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Description

When: During a pre-defined DBA maintenance windows

Prerequisites: https://wikitech.wikimedia.org/wiki/MariaDB/Primary_switchover

  • Team calendar invite

Affected wikis:: https://noc.wikimedia.org/conf/highlight.php?file=dblists/s6.dblist

Checklist:

NEW primary: db1131
OLD primary: db1173

  • Check configuration differences between new and old primary:
sudo pt-config-diff --defaults-file /root/.my.cnf h=db1173.eqiad.wmnet h=db1131.eqiad.wmnet

Failover prep:

  • Silence alerts on all hosts:
sudo cookbook sre.hosts.downtime --hours 1 -r "Primary switchover s6 T316110" 'A:db-section-s6'
  • Set NEW primary with weight 0 (and depool it from API or vslow/dump groups if it is present).
sudo dbctl instance db1131 set-weight 0
sudo dbctl config commit -m "Set db1131 with weight 0 T316110"
  • Topology changes, move all replicas under NEW primary
sudo db-switchover --timeout=25 --only-slave-move db1173 db1131
  • Disable puppet on both nodes
sudo cumin 'db1173* or db1131*' 'disable-puppet "primary switchover T316110"'

Failover:

  • Log the failover:
!log Starting s6 eqiad failover from db1173 to db1131 - T316110
  • Set section read-only:
sudo dbctl --scope eqiad section s6 ro "Maintenance until 06:15 UTC - T316110"
sudo dbctl config commit -m "Set s6 eqiad as read-only for maintenance - T316110"
  • Check s6 is indeed read-only
  • Switch primaries:
sudo db-switchover --skip-slave-move db1173 db1131
echo "===== db1173 (OLD)"; sudo db-mysql db1173 -e 'show slave status\\G'
echo "===== db1131 (NEW)"; sudo db-mysql db1131 -e 'show slave status\\G'
  • Promote NEW primary in dbctl, and remove read-only
sudo dbctl --scope eqiad section s6 set-master db1131
sudo dbctl --scope eqiad section s6 rw
sudo dbctl config commit -m "Promote db1131 to s6 primary and set section read-write T316110"
  • Restart puppet on both hosts:
sudo cumin 'db1173* or db1131*' 'run-puppet-agent -e "primary switchover T316110"'

Clean up tasks:

  • Clean up heartbeat table(s).
sudo db-mysql db1131 heartbeat -e "delete from heartbeat where file like 'db1173%';"
  • change events for query killer:
events_coredb_master.sql on the new primary db1131
events_coredb_slave.sql on the new slave db1173
sudo dbctl instance db1173 set-candidate-master --section s6 true
sudo dbctl instance db1131 set-candidate-master --section s6 false
(dborch1001): sudo orchestrator-client -c untag -i db1131 --tag name=candidate
(dborch1001): sudo orchestrator-client -c tag -i db1173 --tag name=candidate
sudo db-mysql db1115 zarcillo -e "select * from masters where section = 's6';"
  • (If needed): Depool db1173 for maintenance.
sudo dbctl instance db1173 depool
sudo dbctl config commit -m "Depool db1173 T316110"
  • Change db1173 weight to mimic the previous weight db1131:
sudo dbctl instance db1173 edit
  • Apply outstanding schema changes to db1173 (if any)
  • Update/resolve this ticket.

Event Timeline

Change 826281 had a related patch set uploaded (by Gerrit maintenance bot; author: Gerrit maintenance bot):

[operations/puppet@production] mariadb: Promote db1131 to s6 master

https://gerrit.wikimedia.org/r/826281

Change 826282 had a related patch set uploaded (by Gerrit maintenance bot; author: Gerrit maintenance bot):

[operations/dns@master] wmnet: Update s6-master alias

https://gerrit.wikimedia.org/r/826282

Ladsgroup triaged this task as Medium priority.
Ladsgroup moved this task from Triage to Ready on the DBA board.
Ladsgroup added a project: User-notice.
Ladsgroup added a subscriber: Ladsgroup.

Scheduled for next week Tuesday (30th August)

Mentioned in SAL (#wikimedia-operations) [2022-08-30T05:10:31Z] <ladsgroup@cumin1001> START - Cookbook sre.hosts.downtime for 1:00:00 on 25 hosts with reason: Primary switchover s6 T316110

Mentioned in SAL (#wikimedia-operations) [2022-08-30T05:10:49Z] <ladsgroup@cumin1001> END (PASS) - Cookbook sre.hosts.downtime (exit_code=0) for 1:00:00 on 25 hosts with reason: Primary switchover s6 T316110

Mentioned in SAL (#wikimedia-operations) [2022-08-30T05:11:06Z] <ladsgroup@cumin1001> dbctl commit (dc=all): 'Set db1131 with weight 0 T316110', diff saved to https://phabricator.wikimedia.org/P33636 and previous config saved to /var/cache/conftool/dbconfig/20220830-051106-ladsgroup.json

Change 826281 merged by Ladsgroup:

[operations/puppet@production] mariadb: Promote db1131 to s6 master

https://gerrit.wikimedia.org/r/826281

Mentioned in SAL (#wikimedia-operations) [2022-08-30T06:00:18Z] <Amir1> Starting s6 eqiad failover from db1173 to db1131 - T316110

Mentioned in SAL (#wikimedia-operations) [2022-08-30T06:00:26Z] <ladsgroup@cumin1001> dbctl commit (dc=all): 'Set s6 eqiad as read-only for maintenance - T316110', diff saved to https://phabricator.wikimedia.org/P33646 and previous config saved to /var/cache/conftool/dbconfig/20220830-060026-ladsgroup.json

Mentioned in SAL (#wikimedia-operations) [2022-08-30T06:01:09Z] <ladsgroup@cumin1001> dbctl commit (dc=all): 'Promote db1131 to s6 primary and set section read-write T316110', diff saved to https://phabricator.wikimedia.org/P33647 and previous config saved to /var/cache/conftool/dbconfig/20220830-060109-ladsgroup.json

Change 826282 merged by Ladsgroup:

[operations/dns@master] wmnet: Update s6-master alias

https://gerrit.wikimedia.org/r/826282

Mentioned in SAL (#wikimedia-operations) [2022-08-30T06:05:44Z] <ladsgroup@cumin1001> dbctl commit (dc=all): 'Depool db1173 T316110 T312984 T312863 T316186', diff saved to https://phabricator.wikimedia.org/P33649 and previous config saved to /var/cache/conftool/dbconfig/20220830-060543-ladsgroup.json

Ladsgroup updated the task description. (Show Details)
Ladsgroup removed a project: Patch-For-Review.