Bill Farner created MESOS-422:
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Summary: Master leader election should be more robust to stale
ephemeral nodes
Key: MESOS-422
URL: https://issues.apache.org/jira/browse/MESOS-422
Project: Mesos
Issue Type: Bug
Components: master
Reporter: Bill Farner
Priority: Minor
When a leading master exits abruptly, it may fatefully restart and think it's
the leader. If particularly unlucky, this could result in a set of masters
that are indefinitely unstable.
Sequence of events:
- Master process becomes leader
- Master process exits, session expiration counter begins
- Master process restarts, reads leader node contents, and decides it's the
leader (based on PID equality)
- Previous master session expires, node is deleted
- Master decides a different master is leader, commits suicide
- Rinse, repeat for newly-created master node
The salient fact here is that leaders should be concerned with "did i create
the leader node" (ignoring node data) while clients want to be apprised of
leader's node data.
Relevant code:
https://github.com/apache/mesos/blob/trunk/src/detector/detector.cpp#L548
ZK leader election recipe, for reference:
http://zookeeper.apache.org/doc/trunk/recipes.html#sc_leaderElection
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