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From "Enis Soztutar (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-13937) Partially revert HBASE-13172
Date Fri, 19 Jun 2015 19:04:01 GMT

    [ https://issues.apache.org/jira/browse/HBASE-13937?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14593797#comment-14593797

Enis Soztutar commented on HBASE-13937:

[~Apache9] we have a fencing mechanism for region servers already via using HDFS {{recoverLease()}}.
Once the zk session expiry happens, master renames the WAL directory for the RS and also starts
recoverLease on all WAL files, thus guaranteeing that the region server cannot accept any
more writes.  

> Partially revert HBASE-13172 
> -----------------------------
>                 Key: HBASE-13937
>                 URL: https://issues.apache.org/jira/browse/HBASE-13937
>             Project: HBase
>          Issue Type: Sub-task
>          Components: Region Assignment
>            Reporter: Enis Soztutar
>            Assignee: Enis Soztutar
>             Fix For: 0.98.14, 1.2.0, 1.1.1, 1.3.0
>         Attachments: hbase-13937_v1.patch, hbase-13937_v2.patch
> HBASE-13172 is supposed to fix a UT issue, but causes other problems that parent jira
(HBASE-13605) is attempting to fix. 
> However, HBASE-13605 patch v4 uncovers at least 2 different issues which are, to put
it mildly, major design flaws in AM / RS. 
> Regardless of 13605, the issue with 13172 is that we catch {{ServerNotRunningYetException}}
from {{isServerReachable()}} and return false, which then puts the Server to the {{RegionStates.deadServers}}
list. Once it is in that list, we can still assign and unassign regions to the RS after it
has started (because regular assignment does not check whether the server is in  {{RegionStates.deadServers}}.
However, after the first assign and unassign, we cannot assign the region again since then
the check for the lastServer will think that the server is dead. 
> It turns out that a proper patch for 13605 is very hard without fixing rest of  broken
AM assumptions (see HBASE-13605, HBASE-13877 and HBASE-13895 for a colorful history). For
1.1.1, I think we should just revert parts of HBASE-13172 for now. 

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