[GitHub] [incubator-druid] gianm opened a new pull request #7447: Coordinator: Allow dropping all segments.

[GitBox <gi...@apache.org>]

gianm opened a new pull request #7447: Coordinator: Allow dropping all segments.
URL: https://github.com/apache/incubator-druid/pull/7447
 
 
   Removes the coordinator sanity check that prevents it from dropping all
   segments. It's useful to get rid of this, since the behavior is
   unintuitive for dev/testing clusters where users might regularly want
   to drop all their data to get back to a clean slate.
   
   But the sanity check was there for a reason: to prevent a race condition
   where the coordinator might drop all segments if it ran before the
   first metadata store poll finished. This patch addresses that concern
   differently, by allowing methods in MetadataSegmentManager to return
   null if a poll has not happened yet, and canceling coordinator runs
   in that case.
   
   This patch also makes the "dataSources" reference in
   SQLMetadataSegmentManager volatile. I'm not sure why it wasn't volatile
   before, but it seems necessary to me: it's not final, and it's dereferenced
   from multiple threads without synchronization.

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