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From "stack (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-17718) Difference between RS's servername and its ephemeral node cause SSH stop working
Date Sat, 04 Mar 2017 22:29:46 GMT

    [ https://issues.apache.org/jira/browse/HBASE-17718?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15895905#comment-15895905
] 

stack commented on HBASE-17718:
-------------------------------

.002 fixes test failures. Patch exposed sloppyness in our accounting around Master startup
waiting on regions to report-in. We were passing out the wait threshold early but before-the-patch,
things would 'work' because of early registration by RS up in zk. Now fix math so if a Master
that only hosts hbase:meta region, add one so we wait on a RS to checkin to which we can assign
user-space regions.

> Difference between RS's servername and its ephemeral node cause SSH stop working
> --------------------------------------------------------------------------------
>
>                 Key: HBASE-17718
>                 URL: https://issues.apache.org/jira/browse/HBASE-17718
>             Project: HBase
>          Issue Type: Bug
>    Affects Versions: 2.0.0, 1.2.4, 1.1.8
>            Reporter: Allan Yang
>            Assignee: Allan Yang
>         Attachments: HBASE-17718.master.001.patch, HBASE-17718.master.002.patch
>
>
> After HBASE-9593, RS put up an ephemeral node in ZK before reporting for duty. But if
the hosts config (/etc/hosts) is different between master and RS, RS's serverName can be different
from the one stored the ephemeral zk node. The email metioned in HBASE-13753 (http://mail-archives.apache.org/mod_mbox/hbase-user/201505.mbox/%3CCANZDn9ueFEEuZMx=pZdmtLsdGLyZz=rrm1N6EQvLswYc1z-H=g@mail.gmail.com%3E)
is exactly what happened in our production env. 
> But what the email didn't point out is that the difference between serverName in RS and
zk node can cause SSH stop to work. as we can see from the code in {{RegionServerTracker}}
> {code}
>   @Override
>   public void nodeDeleted(String path) {
>     if (path.startsWith(watcher.rsZNode)) {
>       String serverName = ZKUtil.getNodeName(path);
>       LOG.info("RegionServer ephemeral node deleted, processing expiration [" +
>         serverName + "]");
>       ServerName sn = ServerName.parseServerName(serverName);
>       if (!serverManager.isServerOnline(sn)) {
>         LOG.warn(serverName.toString() + " is not online or isn't known to the master."+
>          "The latter could be caused by a DNS misconfiguration.");
>         return;
>       }
>       remove(sn);
>       this.serverManager.expireServer(sn);
>     }
>   }
> {code}
> The server will not be processed by SSH/ServerCrashProcedure. The regions on this server
will not been assigned again until master restart or failover.
> I know HBASE-9593 was to fix the issue if RS report to duty and crashed before it can
put up a zk node. It is a very rare case(And controllableļ¼Œ just fix the bug making rs to
crash). But The issue I metioned can happened more often(and uncontrollable, can't be fixed
in HBase, due to DNS, hosts config, etc.) and have more severe consequence.
> So here I offer some solutions to discuss:
> 1. Revert HBASE-9593 from all branches, Andrew Purtell has reverted it in branch-0.98
> 2. Abort RS if master return a different name, otherwise SSH can't work properly
> 3. Master accepts whatever servername reported by RS and don't change it.
> 4.correct the zk node if master return another name( idea from Ted Yu)
>  



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