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From "Alexander Shraer (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (ZOOKEEPER-1807) Observers spam each other creating connections to the election addr
Date Mon, 04 Nov 2013 21:24:19 GMT

    [ https://issues.apache.org/jira/browse/ZOOKEEPER-1807?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13813287#comment-13813287
] 

Alexander Shraer commented on ZOOKEEPER-1807:
---------------------------------------------

This part is described in Section 3.2 of the paper: https://www.usenix.org/system/files/conference/atc12/atc12-final74.pdf
Of course the paper doesn't talk about FastLeaderElection and things like that. So the actual
implementation needs to have comments, and it does have them in many places, here we should
probably explain some more. 

> 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: Germán Blanco
>             Fix For: 3.5.0
>
>         Attachments: ZOOKEEPER-1807-alex.patch, ZOOKEEPER-1807.patch, notifications-loop.png
>
>
> 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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