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From "Nitay Joffe (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HBASE-1311) ZooKeeperWrapper: Failed to set watcher on ZNode /hbase/master
Date Tue, 07 Apr 2009 20:33:13 GMT

    [ https://issues.apache.org/jira/browse/HBASE-1311?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12696730#action_12696730

Nitay Joffe commented on HBASE-1311:

Hi Andrew,

I like the idea of the reinit() with the ephemeral node map.

However this patch fundamentally changes a lot of things in the design of ZooKeeperWrapper.
The initial idea was not to have any retries in ZooKeeperWrapper so that each user of it can
handle it differently. Each ZooKeeper operation was supposed to either succeed or fail simply
and the code calling it would do what it needs.

Take a look at how I handled SessionExpired in the client, TableServers. I think it is much
cleaner to have each ZooKeeper user (TableServers, HRegionServer, and HMaster) register itself
as a watcher and handle SessionExpired for itself. SessionExpired is not something that is
particular to a single operation, so littering every ZooKeeper call with it seems a bit much?


> ZooKeeperWrapper: Failed to set watcher on ZNode /hbase/master
> --------------------------------------------------------------
>                 Key: HBASE-1311
>                 URL: https://issues.apache.org/jira/browse/HBASE-1311
>             Project: Hadoop HBase
>          Issue Type: Bug
>            Reporter: Andrew Purtell
>            Assignee: Nitay Joffe
>         Attachments: dumb-wrapper-hack.patch
> After about 12 hours of operation, this repeats over and over in the regionserver log:
> 2009-04-05 19:44:38,445 WARN org.apache.hadoop.hbase.zookeeper.ZooKeeperWrapper: Failed
to set watcher on ZNode /hbase/master
> org.apache.zookeeper.KeeperException$SessionExpiredException: KeeperErrorCode = Session
> 	at org.apache.zookeeper.KeeperException.create(KeeperException.java:118)
> 	at org.apache.zookeeper.ZooKeeper.exists(ZooKeeper.java:709)
> 	at org.apache.hadoop.hbase.zookeeper.ZooKeeperWrapper.watchMasterAddress(ZooKeeperWrapper.java:235)
> 	at org.apache.hadoop.hbase.regionserver.HRegionServer.watchMasterAddress(HRegionServer.java:343)
> 	at org.apache.hadoop.hbase.regionserver.HRegionServer.process(HRegionServer.java:339)
> 	at org.apache.zookeeper.ClientCnxn$EventThread.run(ClientCnxn.java:366)
> 2009-04-05 19:44:38,445 WARN org.apache.hadoop.hbase.regionserver.HRegionServer: Unable
to set watcher on ZooKeeper master address. Retrying.

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