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From "Yannis Pavlidis" <ypavli...@oneriot.com>
Subject RE: ROOT table does not get re-assigned
Date Thu, 15 Oct 2009 18:16:32 GMT
Hey Ryan,

I performed additional testing with some alternate configurations and the problem arises (ONLY)
when there is only one regionserver left which has the META table already assigned to it.

In this case the ROOT table does not get assigned to the last regionserver (which holds the
META table).

Interestingly enough though when there is only one regionserver left that has the ROOT table
already assign to it then it can also have the META table re-assigned to it (if again is the
only server - i.e. in this scenario you can have one regionserver holding both the META and
ROOT tables).

Unless I am missing something I cannot find any reason why we cannot assign the ROOT table
to the regionserver that manages the META table if it is the only one remaining (again it
is an extreme case I agree that this can happen).

I applied and tested a fix (at the hbase-0.20.0 codebase) in the RegionManager::regionsAwaitingAssignment
where I add the root table in the regionstoAssign set if the it is the metaServer and also
the only server.

Here is the diff:

diff RegionManager.java.FIXES RegionManager.java
<       if ((!isMetaServer) || (isMetaServer && isSingleServer)) {
>       if (!isMetaServer) {

Let me know what you guys think.



-----Original Message-----
From: Ryan Rawson [mailto:ryanobjc@gmail.com]
Sent: Wed 10/14/2009 5:58 PM
To: hbase-user@hadoop.apache.org
Subject: Re: ROOT table does not get re-assigned

Next time, you can use a service like pastebin.com or anything else like that.

So the log looks ok until the end. At that point, the master is
relying on a regionserver heartbeat back to the master so that the
master has a chance to direct the regionserver. But looks like the 3rd
and last regionserver doesnt check in?

You say this is highly reproducible?  Are you able to run your test on
more machines? A 3 node cluster is a little light, i wouldnt consider
running HBase and HDFS on < 10 nodes for production.  It could be an
artifact of having only 3 nodes too...


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