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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 Fri, 03 Mar 2017 06:47:45 GMT

    [ https://issues.apache.org/jira/browse/HBASE-17718?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15893823#comment-15893823

stack commented on HBASE-17718:

Looking at this now [~allan163]. Yes, revert of HBASE-9593. In the old days, there was all
kinds of mess possible when RS and Master did not agree on naming so we just let master be
in charge of how servers are named in a cluster. HBASE-9593 mangled this.  HBASE-13753 was
supposed to fix it but was just left sit.

But I'd like to put in place an alternate solution for the problem reported by HBASE-9593.
It is a real possibility. The heartbeat registers the server but we need the evaporation of
the znode for the server to be removed from online list -- and if we fail to write the znode
post the heartbeat that reports-for-duty, the removal never happens (My 'There is also something
odd...' is actually incorrect on reexamination).

I'll be back....HBASE-9593 has a nice test that I can reuse.

> 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
> 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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