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From Tharindu Kumara <zonik.hatkum...@gmail.com>
Subject Sessions Expire due to Network partitioning in Zookeeper
Date Wed, 01 Mar 2017 11:25:08 GMT
​Recently, carried out a test to to find the behavior of clients when a
client is partitioned from the ensemble.

Here I used a ensemble of 3 zookeeper servers called A, B and C. And quorum
was set up like below.

A - Follower
B - Leader
C - Follower​

A  <---> B <---> C
   \____________/

And 3 clients are connected to ensemble like below.

C1 is connected A
C2 is connected B
C3 is connected C.

I used iptables to remove the network link between B and C.

command used: iptables -I INPUT -s 123.123.45.123 -j DROP

After removing the link connections looks like below.

A  <----> B         C
   \____________/

Simply there is no way to communicate from B to C and vice versa.

Here What I noticed is that the client connected to Zookeeper Server "C",
could not connect to the ensemble resulting a session expiration timeout.

For this experiment I used tickTime of 3000ms and client session expiration
timeout of 45000ms. And tested with different combinations also.

Can someone please explain what is the root cause for this behavior?

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