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https://issues.apache.org/jira/browse/ZOOKEEPER-2819?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16071482#comment-16071482
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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_r125173093
--- Diff: src/java/main/org/apache/zookeeper/server/quorum/Learner.java ---
@@ -374,6 +374,13 @@ else if (qp.getType() == Leader.SNAP) {
// The leader is going to dump the database
// db is clear as part of deserializeSnapshot()
zk.getZKDatabase().deserializeSnapshot(leaderIs);
+ // ZOOKEEPER-2819: overwrite config node content extracted
+ // from leader snapshot with local config, to avoid
potential
+ // inconsistency of config node content during rolling
restart.
+ if (!QuorumPeerConfig.isReconfigEnabled()) {
--- End diff --
@shralex instead of avoiding deserializing the config zNode we could
overwrite the deserialized zNode content with local quorum config. Test will be
covered in the test improvement JIRA ZOOKEEPER-2828.
> 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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