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https://issues.apache.org/jira/browse/HBASE-4455?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13114081#comment-13114081
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Ted Yu commented on HBASE-4455:
-------------------------------
I am running whole test suite based on patch v3 and TRUNK. Will update with
test results.
> Rolling restart RSs scenario, -ROOT-, .META. regions are lost in
> AssignmentManager
> ----------------------------------------------------------------------------------
>
> Key: HBASE-4455
> URL: https://issues.apache.org/jira/browse/HBASE-4455
> Project: HBase
> Issue Type: Bug
> Reporter: Ming Ma
> Assignee: Ming Ma
> Fix For: 0.92.0
>
>
> Keep Master up all the time, do rolling restart of RSs like this - stop RS1,
> wait for 2 seconds, stop RS2, start RS1, wait for 2 seconds, stop RS3, start
> RS2, wait for 2 seconds, etc. After a while, you will find the -ROOT-, .META.
> regions aren't in "regions in transtion" from AssignmentManager point of
> view, but they aren't assigned to any regions. Here are the issues.
> 1. .-ROOT- or .META. location is stale when MetaServerShutdownHandler is
> invoked to check if it contains -ROOT- region. That is due to long delay from
> ZK notification and async nature of the system. Here is an example, even
> though new root region server sea-lab-1,60020,1316380133656 is set at T2, at
> T3 the shutdown process for sea-lab-1,60020,1316380133656, the root location
> still points to old server sea-lab-3,60020,1316380037898.
> T1: 2011-09-18 14:08:52,470 DEBUG org.apache.hadoop.hbase.zookeeper.ZKUtil:
> master:6
> 0000-0x1327e43175e0000 Retrieved 29 byte(s) of data from znode
> /hbase/root-regio
> n-server and set watcher; sea-lab-3,60020,1316380037898
> T2: 2011-09-18 14:08:57,173 INFO
> org.apache.hadoop.hbase.catalog.RootLocationEditor: Setting ROOT region
> location in ZooKeeper as sea-lab-1,60020,1316380133656
> T3: 2011-09-18 14:10:26,393 DEBUG
> org.apache.hadoop.hbase.master.ServerManager: Adde
> d=sea-lab-1,60020,1316380133656 to dead servers, submitted shutdown handler
> to be executed, root=false, meta=true, current Root Location:
> sea-lab-3,60020,1316380037898
> T4: 2011-09-18 14:12:37,314 DEBUG org.apache.hadoop.hbase.zookeeper.ZKUtil:
> master:6
> 0000-0x1327e43175e0000 Retrieved 29 byte(s) of data from znode
> /hbase/root-region-server and set watcher; sea-lab-1,60020,1316380133656
> 2. The MetaServerShutdownHandler worker thread that waits for -ROOT- or
> .META. availability could be blocked. If meanwhile, the new server that
> -ROOT- or .META. is being assigned restarted, another instance of
> MetaServerShutdownHandler is queued. Eventually, all
> MetaServerShutdownHandler worker threads are filled up. It looks like
> HBASE-4245.
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