s1 primary master db1052 needs to be decommissioned (T186320) and it is also blocking row B switch upgrade (T183585)
The candidate master is db1067.
This a checklist of what needs to be done before the failover
[x] Verify db1067 has STATEMENT as binlog format
[] Upgrade micro-code and reboot on db1067
or
[x] Reimage db1067 to stretch/10.1 and check the latest micro-code is installed and active (?)
[x] Pick a date for the failover: July 18th (Wednesday) at 06:00AM UTC
[x] Communicate liaisons to handle the read only time T197134
[x] Pick and prepare a new candidate master (db1089 - row C, which has already been migrated to the new switch)
* [] Change this to db1083 once db1067 is the master
[] Prepare and do the actual failover (template for the steps: https://wikitech.wikimedia.org/wiki/MariaDB#Production_section_failover_checklist)