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https://issues.apache.org/jira/browse/ZOOKEEPER-1748?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13754565#comment-13754565
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Nikita Vetoshkin commented on ZOOKEEPER-1748:
---------------------------------------------
I think using TCP keepalive can mitigate this issue, but better approach would
be using application level pings. E.g. on my Linux box keepalive value is set
to 2 hours:{{net.ipv4.tcp_keepalive_time = 7200}}.
> 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: 3.5.0, 3.4.5
> Environment: Linux, Java 1.7
> Reporter: Antal Sasvári
> Priority: Minor
> Fix For: 3.5.0
>
>
> 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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