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From "Jim Kellerman (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HBASE-1736) If RS can't talk to master, pause; more importantly, don't split (Currently we do and splits are lost and table is wounded)
Date Mon, 03 Aug 2009 00:27:14 GMT

    [ https://issues.apache.org/jira/browse/HBASE-1736?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12738157#action_12738157
] 

Jim Kellerman commented on HBASE-1736:
--------------------------------------

Heartbeat and communication between Master and HRS in 0.21 should be greatly reduced, with
region assignment happening via ZK, so this should be somewhat less of an issue at that time.
However, I
agree that the HRS can continue so long as it does not need to split.

The problem is, what do we do when we reach that point?
- Put the cluster into "real-safe-mode" where no requests are accepted from clients?
- Make the cluster read-only?

Both of the above would exit that mode when a new master is available.

If we do region assignment more at the HRS level and use the master for just scanning for
unassigned
regions so it can put them into a pool, the master becomes much less significant. The HRS
could update the .META. and place the split children into the unassigned pool.


> If RS can't talk to master, pause; more importantly, don't split (Currently we do and
splits are lost and table is wounded)
> ---------------------------------------------------------------------------------------------------------------------------
>
>                 Key: HBASE-1736
>                 URL: https://issues.apache.org/jira/browse/HBASE-1736
>             Project: Hadoop HBase
>          Issue Type: Bug
>            Reporter: stack
>             Fix For: 0.20.1
>
>
> What I saw was master shutting itself down because it had lost zk lease.  Fine.   The
RS though doesn't look like it can deal with this situation.    We'll see stuff like this:
> {code}
> ...failed on connection exception: java.net.ConnectException: Connection refused
>     at org.apache.hadoop.hbase.ipc.HBaseClient.wrapException(HBaseClient.java:744)
>     at org.apache.hadoop.hbase.ipc.HBaseClient.call(HBaseClient.java:722)
>     at org.apache.hadoop.hbase.ipc.HBaseRPC$Invoker.invoke(HBaseRPC.java:328)
>     at $Proxy0.regionServerReport(Unknown Source)
>     at org.apache.hadoop.hbase.regionserver.HRegionServer.run(HRegionServer.java:470)
>     at java.lang.Thread.run(Unknown Source)
> Caused by: java.net.ConnectException: Connection refused
>     at sun.nio.ch.SocketChannelImpl.checkConnect(Native Method)
>     at sun.nio.ch.SocketChannelImpl.finishConnect(Unknown Source)
>     at org.apache.hadoop.net.SocketIOWithTimeout.connect(SocketIOWithTimeout.java:206)
>     at org.apache.hadoop.net.NetUtils.connect(NetUtils.java:404)
>     at org.apache.hadoop.hbase.ipc.HBaseClient$Connection.setupIOstreams(HBaseClient.java:305)
>     at org.apache.hadoop.hbase.ipc.HBaseClient.getConnection(HBaseClient.java:826)
>     at org.apache.hadoop.hbase.ipc.HBaseClient.call(HBaseClient.java:707)
>     ... 4 more
> {code}
> ... all over the regionserver as it tries to send heartbeat to master on this broken
connection.
> On split, we close parent, add children to the catalog but then when we try to tell the
master about the split, it fails.  Means the children never get deployed.  Meantime  the parent
is offline.
> This issue is about going through the regionserver and anytime it has a connection to
master, make sure on fault that no damage is done the table and then that the regionserver
puts a pause on splitting.

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