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https://issues.apache.org/jira/browse/ZOOKEEPER-1748?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15531799#comment-15531799
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ASF GitHub Bot commented on ZOOKEEPER-1748:
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GitHub user gnethercutt opened a pull request:
https://github.com/apache/zookeeper/pull/83
enable TCP keepalive for the leadership election/quorum socket
Use TCP keep-alives for election/quorum peer connections.
This is the shortest edit distance to address
[ZOOKEEPER-1748](https://issues.apache.org/jira/browse/ZOOKEEPER-1748), and is
required to avoid silent packet delivery failures for a long-lived connection
in AWS (amongst other environments).
See also:
- [VPC security group connection
tracking](https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/using-network-security.html#security-group-connection-tracking)
- [Using TCP
keepalives](http://tldp.org/HOWTO/TCP-Keepalive-HOWTO/usingkeepalive.html)
- [Zookeeper
internals](https://zookeeper.apache.org/doc/r3.4.8/zookeeperInternals.html)
You can merge this pull request into a Git repository by running:
$ git pull https://github.com/gnethercutt/zookeeper election_tcp_keepalive
Alternatively you can review and apply these changes as the patch at:
https://github.com/apache/zookeeper/pull/83.patch
To close this pull request, make a commit to your master/trunk branch
with (at least) the following in the commit message:
This closes #83
----
commit bcab41003d91dc121e368337317710c2434bece8
Author: Glenn Nethercutt <[email protected]>
Date: 2016-09-28T18:22:41Z
enable TCP keepalive for the leadership election/quorum socket
----
> 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
> Assignee: Daniel Peon
> Priority: Minor
> Fix For: 3.5.3, 3.6.0
>
> Attachments: Zookeeper-1748-add_tcp_keepalive.patch
>
>
> 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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