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From "Raul Gutierrez Segales (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (ZOOKEEPER-1807) Observers spam each other creating connections to the election addr
Date Sat, 02 Nov 2013 03:31:18 GMT

    [ https://issues.apache.org/jira/browse/ZOOKEEPER-1807?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13811858#comment-13811858
] 

Raul Gutierrez Segales commented on ZOOKEEPER-1807:
---------------------------------------------------

I think what's happening is that when we send the initial notifications to all members, as
opposed to just voting members as it was before, we trigger off a self-replicating cascade
of notifications. Each Observers gets the notification and then by virtue of:

{noformat}
                        /*                                                               
                                                            
                         * If it is from a non-voting server (such as an observer or     
                                                            
                         * a non-voting follower), respond right away.                   
                                                            
                         */
                        if(!self.getVotingView().containsKey(response.sid)){
                           .....
                        }
{noformat}

it replies back to each Observer and so on.  So sounds to me that this needs to match what
we have  in sendNotifications and actually check response.sid against self.getAllKnownServerIds()
to avoid the endless echoing of notifications that I am seeing.

Thoughts [~shralex], [~fpj] ?

> Observers spam each other creating connections to the election addr
> -------------------------------------------------------------------
>
>                 Key: ZOOKEEPER-1807
>                 URL: https://issues.apache.org/jira/browse/ZOOKEEPER-1807
>             Project: ZooKeeper
>          Issue Type: Bug
>            Reporter: Raul Gutierrez Segales
>            Assignee: Raul Gutierrez Segales
>             Fix For: 3.5.0
>
>
> Hey [~shralex],
> I noticed today that my Observers are spamming each other trying to open connections
to the election port. I've got tons of these:
> {noformat}
> 2013-11-01 22:19:45,819 - DEBUG [WorkerSender[myid=13]] - There is a connection already
for server 9
> 2013-11-01 22:19:45,819 - DEBUG [WorkerSender[myid=13]] - There is a connection already
for server 10
> 2013-11-01 22:19:45,819 - DEBUG [WorkerSender[myid=13]] - There is a connection already
for server 6
> 2013-11-01 22:19:45,819 - DEBUG [WorkerSender[myid=13]] - There is a connection already
for server 12
> 2013-11-01 22:19:45,819 - DEBUG [WorkerSender[myid=13]] - There is a connection already
for server 14
> {noformat}
> and so and so on ad nauseam. 
> Now, looking around I found this inside FastLeaderElection.java from when you committed
ZOOKEEPER-107:
> {noformat}
>      private void sendNotifications() {
> -        for (QuorumServer server : self.getVotingView().values()) {
> -            long sid = server.id;
> -
> +        for (long sid : self.getAllKnownServerIds()) {
> +            QuorumVerifier qv = self.getQuorumVerifier();
> {noformat}
> Is that really desired? I suspect that is what's causing Observers to try to connect
to each other (as opposed as just connecting to participants). I'll give it a try now and
let you know. (Also, we use observer ids that are > 0, and I saw some parts of the code
that might not deal with that assumption - so it could be that too..). 



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