[jira] [Commented] (ZOOKEEPER-2819) Changing configuration via rolling restart does not work on 3.5.x.

["Alexander Shraer (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/ZOOKEEPER-2819?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16061296#comment-16061296 ] 

Alexander Shraer commented on ZOOKEEPER-2819:
---------------------------------------------

A second issue was raised by Guillermo where one may be using reconfig, but the cluster is partitioned and an admin may want to force a minority of servers to form a cluster (even though this is clearly not safe, since the other majority servers may also have a quorum and continue to operate). 

One idea of how this can be achieved is by setting reconfigEnable parameter to false whenever such manual intervention is made, as a means of manual configuration override that will prevent the server from automatically accepting a configration from other servers.

> Changing 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
>            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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