CMS: Move and rewrite check_unlocked_replicas

[voetberg]

• Use sqla2.0 (broken into base statement and modifications)
• Change gauge to prometheuspusher
• Update Header
• Sort imports
• change except to except Exception

Updated queries compile to:

SELECT count(*) AS count_1 
FROM dev.replicas 
WHERE dev.replicas.tombstone IS NOT NULL AND dev.replicas.tombstone < :tombstone_1

SELECT count(*) AS count_1 
FROM dev.replicas 
WHERE dev.replicas.tombstone IS NOT NULL

The query for expired replicas has the extra condition tombstone < sysdate - 2/24' but I can't get my head around why that offset (of milliseconds?) is there to begin with, so if there need to be modifications let me know.

[dchristidis]

Please consult #140.

[dchristidis]

The query for expired replicas has the extra condition tombstone < sysdate - 2/24' but I can't get my head around why that offset (of milliseconds?) is there to begin with, so if there need to be modifications let me know.

2/24 means two hours. My impression is that it’s as if this probe was written in a different era where all the Reapers run in greedy mode. Hence, tombstone < now is the Reaper backlog and tombstone < now -2h means that something may be wrong.

In my personal opinion, this is pointless. However, it could be that I missed something so I wish to understand how CMS is using this before finalising the move away from common.