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From Shawn Heisey <>
Subject Re: SessionExpiredException
Date Sat, 06 May 2017 12:40:29 GMT
On 5/3/2017 7:32 AM, Satya Marivada wrote:
> I see below exceptions in my logs sometimes. What could be causing it?
> org.apache.zookeeper.KeeperException$SessionExpiredException:

Based on my limited research, this would tend to indicate that the
heartbeats ZK uses to detect when sessions have gone inactive are not
occurring in a timely fashion.

Common causes seem to be:

JVM Garbage collections.  These can cause the entire JVM to pause for an
extended period of time, and this time may exceed the configured timeouts.

Excess client connections to ZK.  ZK limits the number of connections
from each client address, with the idea of preventing denial of service
attacks.  If a client is misbehaving, it may make more connections than
it should.  You can try increasing the limit in the ZK config, but if
this is the reason for the exception, then something's probably wrong,
and you may be just hiding the real problem.

Although we might have bugs causing the second situation, the first
situation seems more likely.


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