Mahadev konar commented on ZOOKEEPER-87:

i was thinking abt the same lines but not on maximum capacity on follower 
handlers -- 

ben and I had a discussion regarding this and we decided on doing htis --- 

1) we send a Leader.PING from the leader to the follower --- we will include 
the ticktime at the leader and send it to the follower

2) the follower just returns back the tick time with the ping response. 

3) we update the ticktime that we saw last from the follower and then kill the 
follower handler if its lagging behind.

-- this approach is less error prone since we are getting response from the 
follower and know whats the last ticktime it processed. The problem with your 
suggestion is that you might be sending it out fast to the follower but the 
follower might be buffering all of it and not doing anything with it... 

though the above suggestion has a problem right now since the Leader.PING does 
not go through the pipeline at the follower. so a response to the ping does not 
necessarily mean that the follower is in line with processing the requests. We 
have to get an end to end response from the follower to see how much it is 

> Follower does not shut itself down if its too far behind the leader.
> --------------------------------------------------------------------
>                 Key: ZOOKEEPER-87
>                 URL: https://issues.apache.org/jira/browse/ZOOKEEPER-87
>             Project: Zookeeper
>          Issue Type: Bug
>            Reporter: Mahadev konar
>            Assignee: Mahadev konar
>            Priority: Critical
>             Fix For: 3.0.0
> Currently, the follower if lagging behind keeps sending pings to the leader 
> it will stay alive and will keep getting further and further behind the 
> leader. The follower should shut itself down if it is not able to keep up to 
> the leader within some limit so that gurantee of updates can be made to the 
> clients connected to different servers.

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