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https://issues.apache.org/jira/browse/ZOOKEEPER-928?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12930785#action_12930785
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Mahadev konar commented on ZOOKEEPER-928:
-----------------------------------------

vishal,
 Here is the definition of setSoTimeout -

{code}
public void setSoTimeout(int timeout)
                  throws SocketException
Enable/disable SO_TIMEOUT with the specified timeout, in milliseconds. With 
this option set to a non-zero timeout, a read() call on the InputStream 
associated with this Socket will block for only this amount of time. If the 
timeout expires, a java.net.SocketTimeoutException is raised, though the Socket 
is still valid. The option must be enabled prior to entering the blocking 
operation to have effect. The timeout must be > 0. A timeout of zero is 
interpreted as an infinite timeout.
{code}

This means is that the read would block till timeout and throw an exception if 
it doesnt hear from the leader during that time. Wouldnt this suffice?

> Follower should stop following and start FLE if it does not receive pings 
> from the leader
> -----------------------------------------------------------------------------------------
>
>                 Key: ZOOKEEPER-928
>                 URL: https://issues.apache.org/jira/browse/ZOOKEEPER-928
>             Project: Zookeeper
>          Issue Type: Bug
>          Components: quorum, server
>    Affects Versions: 3.3.2
>            Reporter: Vishal K
>            Priority: Critical
>             Fix For: 3.3.3, 3.4.0
>
>
> In Follower.followLeader() after syncing with the leader, the follower does:
>                 while (self.isRunning()) {
>                     readPacket(qp);
>                     processPacket(qp);
>                 }
> It looks like it relies on socket timeout expiry to figure out if the 
> connection with the leader has gone down.  So a follower *with no cilents* 
> may never notice a faulty leader if a Leader has a software hang, but the TCP 
> connections with the peers are still valid. Since it has no cilents, it won't 
> hearbeat with the Leader. If majority of followers are not connected to any 
> clients, then FLE will fail even if other followers attempt to elect a new 
> leader.
> We should keep track of pings received from the leader and see if we havent 
> seen
> a ping packet from the leader for (syncLimit * tickTime) time and give up 
> following the
> leader.

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