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From "ASF GitHub Bot (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (ZOOKEEPER-2819) Changing membership configuration via rolling restart does not work on 3.5.x.
Date Tue, 27 Jun 2017 21:12:00 GMT

    [ https://issues.apache.org/jira/browse/ZOOKEEPER-2819?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16065469#comment-16065469
] 

ASF GitHub Bot commented on ZOOKEEPER-2819:
-------------------------------------------

Github user hanm commented on a diff in the pull request:

    https://github.com/apache/zookeeper/pull/292#discussion_r124396899
  
    --- Diff: src/java/main/org/apache/zookeeper/server/quorum/QuorumPeer.java ---
    @@ -1744,9 +1744,14 @@ public void setAcceptedEpoch(long e) throws IOException {
         public boolean processReconfig(QuorumVerifier qv, Long suggestedLeaderId, Long zxid,
boolean restartLE) {
            InetSocketAddress oldClientAddr = getClientAddress();
     
    +       boolean isReconfigEnabled = QuorumPeerConfig.isReconfigEnabled();
            // update last committed quorum verifier, write the new config to disk
    -       // and restart leader election if config changed
    -       QuorumVerifier prevQV = setQuorumVerifier(qv, true);
    +       // and restart leader election if config changed. If reconfig feature is
    +       // not enabled, just set last committed quorum verifier and bail out.
    +       QuorumVerifier prevQV = setQuorumVerifier(qv, isReconfigEnabled);
    --- End diff --
    
    Updated. Now I am returning immediately at the start of processReconfig if the feature
flag is not set. 


> Changing membership configuration via rolling restart does not work on 3.5.x.
> -----------------------------------------------------------------------------
>
>                 Key: ZOOKEEPER-2819
>                 URL: https://issues.apache.org/jira/browse/ZOOKEEPER-2819
>             Project: ZooKeeper
>          Issue Type: Bug
>          Components: quorum, server
>    Affects Versions: 3.5.0, 3.5.1, 3.5.2, 3.5.3
>            Reporter: Michael Han
>            Assignee: Michael Han
>            Priority: Critical
>
> In 3.5.x there is no easy way of changing the membership config using rolling restarts
because of the introduction of dynamic reconfig feature in ZOOKEEPER-107, which automatically
manages membership configuration parameters.
> ZOOKEEPER-2014 introduced a reconfigEnabled flag to turn on / off the reconfig feature.
We can use same flag and when it sets to false, it should disable both in memory and on disk
updates of membership configuration information, besides disabling the reconfig commands on
CLI which ZOOKEEPER-2014 already did, so users can continue using rolling restarts if needed.

> We should also document explicitly the support of membership changes via rolling restarts
will be deprecated at what release time frame and promote reconfig as the replacement.
> The problem was raised at user mailing list by Guillermo Vega-Toro, reference thread:
> http://zookeeper-user.578899.n2.nabble.com/How-to-add-nodes-to-a-Zookeeper-3-5-3-beta-ensemble-with-reconfigEnabled-false-td7583138.html



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