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https://issues.apache.org/jira/browse/HBASE-17718?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15895590#comment-15895590
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stack commented on HBASE-17718:
-------------------------------
First cut at a patch. Reverts the fix for the problem reported over in
HBASE-9593 and instead addresses the reported issue with a check for ephemeral
znode on ConnectionException when trying to open a region; if none found we
clean up the bad online server.
This is simple.
Alternatives such as having a provisional state in the Master where on receipt
of a confirming heartbeat or a check on zk state looking for a corresponding
ephemeral znode for the reporting regionserver and then moving the state from
provisionally registered to actually registered were all messy. They also take
us away from actual fix which is HBASE-17733.
Lets see how this patch does. branch-1 will be a bit different.
> 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
>
>
> 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 controllableļ¼ 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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