[jira] [Commented] (ZOOKEEPER-1355) Add zk.updateServerList(newServerList)

["Hadoop QA (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/ZOOKEEPER-1355?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13473707#comment-13473707 ] 

Hadoop QA commented on ZOOKEEPER-1355:
--------------------------------------

-1 overall.  Here are the results of testing the latest attachment 
  http://issues.apache.org/jira/secure/attachment/12548653/ZOOKEEPER-1355-10-Oct.patch
  against trunk revision 1391526.

    +1 @author.  The patch does not contain any @author tags.

    +1 tests included.  The patch appears to include 31 new or modified tests.

    +1 javadoc.  The javadoc tool did not generate any warning messages.

    -1 javac.  The patch appears to cause tar ant target to fail.

    +1 findbugs.  The patch does not introduce any new Findbugs (version 1.3.9) warnings.

    +1 release audit.  The applied patch does not increase the total number of release audit warnings.

    -1 core tests.  The patch failed core unit tests.

    +1 contrib tests.  The patch passed contrib unit tests.

Test results: https://builds.apache.org/job/PreCommit-ZOOKEEPER-Build/1209//testReport/
Findbugs warnings: https://builds.apache.org/job/PreCommit-ZOOKEEPER-Build/1209//artifact/trunk/build/test/findbugs/newPatchFindbugsWarnings.html
Console output: https://builds.apache.org/job/PreCommit-ZOOKEEPER-Build/1209//console

This message is automatically generated.
                
> Add zk.updateServerList(newServerList) 
> ---------------------------------------
>
>                 Key: ZOOKEEPER-1355
>                 URL: https://issues.apache.org/jira/browse/ZOOKEEPER-1355
>             Project: ZooKeeper
>          Issue Type: New Feature
>          Components: c client, java client
>            Reporter: Alexander Shraer
>            Assignee: Alexander Shraer
>             Fix For: 3.5.0
>
>         Attachments: loadbalancing-more-details.pdf, loadbalancing.pdf, ZOOKEEPER-1355-10-Oct.patch, ZOOKEEPER-1355-ver10-1.patch, ZOOKEEPER-1355-ver10-2.patch, ZOOKEEPER-1355-ver10-3.patch, ZOOKEEPER-1355-ver10-4.patch, ZOOKEEPER-1355-ver10-4.patch, ZOOKEEPER-1355-ver10.patch, ZOOKEEPER-1355-ver11-1.patch, ZOOKEEPER-1355-ver11.patch, ZOOKEEPER-1355-ver12-1.patch, ZOOKEEPER-1355-ver12-2.patch, ZOOKEEPER-1355-ver12-4.patch, ZOOKEEPER-1355-ver12.patch, ZOOKEEPER-1355-ver13.patch, ZOOKEEPER-1355-ver14.patch, ZOOKEEPER-1355-ver2.patch, ZOOKEEPER=1355-ver3.patch, ZOOKEEPER-1355-ver4.patch, ZOOKEEPER-1355-ver5.patch, ZOOKEEPER-1355-ver6.patch, ZOOKEEPER-1355-ver7.patch, ZOOKEEPER-1355-ver8.patch, ZOOKEEPER-1355-ver9-1.patch, ZOOKEEPER-1355-ver9.patch, ZOOOKEEPER-1355.patch, ZOOOKEEPER-1355-test.patch, ZOOOKEEPER-1355-ver1.patch
>
>
> When the set of servers changes, we would like to update the server list stored by clients without restarting the clients.
> Moreover, assuming that the number of clients per server is the same (in expectation) in the old configuration (as guaranteed by the current list shuffling for example), we would like to re-balance client connections across the new set of servers in a way that a) the number of clients per server is the same for all servers (in expectation) and b) there is no excessive/unnecessary client migration.
> It is simple to achieve (a) without (b) - just re-shuffle the new list of servers at every client. But this would create unnecessary migration, which we'd like to avoid.
> We propose a simple probabilistic migration scheme that achieves (a) and (b) - each client locally decides whether and where to migrate when the list of servers changes. The attached document describes the scheme and shows an evaluation of it in Zookeeper. We also implemented re-balancing through a consistent-hashing scheme and show a comparison. We derived the probabilistic migration rules from a simple formula that we can also provide, if someone's interested in the proof.

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