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From Samuel Rash <r...@fb.com>
Subject ephemeral node problem
Date Thu, 17 Feb 2011 21:08:49 GMT

We are running zookeeper 3.3.2 and have seen what appears to be a problem with ephemeral nodes.
 We create about 2000 persistent nodes (leaves) in a hierarchy.  Under each of these, we run
a leader
election with ephemeral nodes (~40).  This results in about 80,000 total ephemeral nodes.
 During restart of our system, the leader elections can churn a bit as hosts remove themselves,
electing new leaders, which then themselves may withdraw from the election.  In one such restart,
we saw an election get 'stuck'.  Upon investigating, one node had it's session expired (indicated
in the zk logs), but one of its ephemeral nodes was still left.  We took down the processes
holdilng ephemeral nodes and this node remained.

Are there any known bugs in zookeeper that might result in this?  it does not appear to happen
under our normal laod.


Sam Rash

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