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From "Ariel Weisberg (JIRA)" <j...@apache.org>
Subject [jira] [Created] (CASSANDRA-13327) Pending endpoints size check for CAS doesn't play nicely with writes-on-replacement
Date Tue, 14 Mar 2017 19:24:41 GMT
Ariel Weisberg created CASSANDRA-13327:
------------------------------------------

             Summary: Pending endpoints size check for CAS doesn't play nicely with writes-on-replacement
                 Key: CASSANDRA-13327
                 URL: https://issues.apache.org/jira/browse/CASSANDRA-13327
             Project: Cassandra
          Issue Type: Bug
          Components: Coordination
            Reporter: Ariel Weisberg
            Assignee: Ariel Weisberg


Consider this ring:

127.0.0.1  MR UP     JOINING -7301836195843364181
127.0.0.2    MR UP     NORMAL -7263405479023135948
127.0.0.3    MR UP     NORMAL -7205759403792793599
127.0.0.4   MR DOWN     NORMAL -7148113328562451251

where 127.0.0.1 was bootstrapping for cluster expansion. Note that, due to the failure of
127.0.0.4, 127.0.0.1 was stuck trying to stream from it and making no progress.

Then the down node was replaced so we had:

127.0.0.1  MR UP     JOINING -7301836195843364181
127.0.0.2    MR UP     NORMAL -7263405479023135948
127.0.0.3    MR UP     NORMAL -7205759403792793599
127.0.0.5   MR UP     JOINING -7148113328562451251

It’s confusing in the ring - the first JOINING is a genuine bootstrap, the second is a replacement.
We now had CAS unavailables (but no non-CAS unvailables). I think it’s because the pending
endpoints check thinks that 127.0.0.5 is gaining a range when it’s just replacing.

The workaround is to kill the stuck JOINING node, but Cassandra shouldn’t unnecessarily
fail these requests.

It also appears like required participants is bumped by 1 during a host replacement so if
the replacing host fails you will get unavailables and timeouts.



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