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From "ASF GitHub Bot (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (ZOOKEEPER-1748) TCP keepalive for leader election connections
Date Mon, 05 Jun 2017 23:41:12 GMT

    [ https://issues.apache.org/jira/browse/ZOOKEEPER-1748?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16037851#comment-16037851

ASF GitHub Bot commented on ZOOKEEPER-1748:

GitHub user bensherman opened a pull request:


    Zookeeper 1748: Add option for tcp keepalive

    As referenced in https://issues.apache.org/jira/browse/ZOOKEEPER-1748 and https://github.com/apache/zookeeper/pull/83,
add the option to use keepalived on quorum connections.  These connections are often idle
and long-lived, thus tend to be silently dropped by intermediate networking infrastructure
(AWS Security Groups' state tables, for example).
    This PR adds the option to use the system's keepalive functionality when creating the
socket for quorum connections.  
    It does not change existing behavior.

You can merge this pull request into a Git repository by running:

    $ git pull https://github.com/bensherman/zookeeper ZOOKEEPER-1748

Alternatively you can review and apply these changes as the patch at:


To close this pull request, make a commit to your master/trunk branch
with (at least) the following in the commit message:

    This closes #274
commit 0f7ece14df76cba5170c0442ebedec31cf6fb4b9
Author: Ben Sherman <bsherman@axon.com>
Date:   2017-06-05T21:56:14Z

    Added option to use tcp keep alives.

commit 820c628ea05fbdd5477083fa77db55a4f0e8812f
Author: Ben Sherman <bsherman@axon.com>
Date:   2017-06-05T22:34:59Z

    document tcpKeepAlive option


> 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: 3.5.4, 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
> I've been told that e.g. Apache ActiveMQ also has a config option for similar purpose
called transport.keepalive.

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