sijie commented on issue #851: Issue 578 : make MajorCompaction controlled by 
time of the day/day of the week
URL: https://github.com/apache/bookkeeper/pull/851#issuecomment-355764759
 
 
   @merlimat 
   
   > With the current bookies, the compaction is times 1h or 24h after the 
restart, so after a rolling restart, the compactions are at least a bit skewed 
by the sequential restart.
   
   yes agreed. they can be started at different time, but if the compaction 
time is longer than your restart duration, you potentially still have all 
bookies compaction at the same time.
   
   randomized jitters have same effects as time-skewed introduced in restart 
sequence.
   
   > Another approach would be to configure something like that at most 20% of 
bookies can be doing compaction at the same time, though it gets a bit more 
involved as a change, and also it could be problematic if compaction is taking 
very long times.
   
   yes that requires some sort of coordination. it is kind of getting things 
complicated. I think a randomized jitter approach is probably 'good' enough.
   
   so ideally people can just configure compaction, auditor checks either at 
rate or at cron, with potentially applied jitters.
   
   rate expression: `rate(x minutes)`
   cron expression: `cron(...)`
   with jitter: `jitter(x minutes)`
   
   so a compaction setting:
   
   compaction: `rate(60 minutes) withJitter(10 minutes)` => run  compaction 
every 60 minutes, with a randomized jitter of 10 minutes.
   compaction: `cron(...) withJitter(10 minutes)` => run  compaction in a cron 
expression, injecting a randomized jitter of 10 minutes.
   auditorCheck: `cron(..)` => schedule auditor check at a given time.
   

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