Antal Sasvári created ZOOKEEPER-1748:
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Summary: TCP keepalive for leader election connections
Key: ZOOKEEPER-1748
URL: https://issues.apache.org/jira/browse/ZOOKEEPER-1748
Project: ZooKeeper
Issue Type: Improvement
Components: leaderElection
Affects Versions: 3.4.5, 3.5.0
Environment: Linux, Java 1.7
Reporter: Antal Sasvári
Priority: Minor
Fix For: 3.5.0, 3.4.6
In our system we encountered the following problem:
If the system is stable, and there is no leader election, the leader election
port connections are open for very long time without any packets being sent on
them.
Some network elements silently drop the established TCP connection after a
timeout if there are no packets being sent on it. In this case the ZK servers
will not notice the connection loss. This causes additional delay later when
the next leader election is started, as the TCP connections are not alive any
more.
We would like to be able to enable TCP keepalive on the leader election sockets
in order to prevent the connection timeout in some network elements due to
connection inactivity.
This could be controlled by adding a new config parameter called tcpKeepAlive
in the ZooKeeper configuration file. It would be only applicable in case of
algorithm 3 (TCP based fast leader election), having the default value false.
If tcpKeepAlive is set to true, the TCP keepalive flag should be enabled for
the leader election sockets in QuorumCnxManager.setSockOpts() by calling
sock.setKeepAlive(true).
We have tested this change successfully in our environment.
Please comment whether you see any problem with this. If not, I am going to
submit a patch.
I've been told that e.g. Apache ActiveMQ also has a config option for similar
purpose called transport.keepalive.
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