Re: [PR] perf: allow follower coordinators to pre-fill segment cache for faster leadership assumption via delta sync (druid)

["kfaraz (via GitHub)" <gi...@apache.org>]

kfaraz commented on PR #19644:
URL: https://github.com/apache/druid/pull/19644#issuecomment-4854848586

   > My proposed solution is allow follower Coordinator replicas to also fill their cache and rely on a delta sync upon becoming the leader. The delta sync is a much cheaper operation and allows the Coordinator to come up faster with a healthy cache. While this faster recovery/higher availability is at the expense of higher DB load, this is particularly useful for situations like rolling deployments where you may only have > 1 coordinators running for a short period (then back to 1).
   
   @jtuglu1 , this is already the case. Follower coordinator/overlords already perform delta syncs in the background.
   Only the first sync (that happens upon startup) is a full sync for both Leader and Follower.
   This can be verified from logs as well as cache metrics.
   
   Please let me know if you have noticed otherwise.


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