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From Ted Yu <yuzhih...@gmail.com>
Subject Re: load balancing considerations
Date Wed, 11 Aug 2010 04:30:20 GMT
We use 0.20.6 with HBASE-2473
As you can see from the following region server log snippet, OOME happened
to this RS:

2010-08-11 03:59:12,760 INFO org.apache.hadoop.hbase.regionserver.HRegion:
Blocking updates for 'IPC Server handler 17 on 60020' on region
2__HB_NOINC_GRID_0809-THREEGPPSPEECHCALLS-1281499094297,\x0E\x0E\x0E\x0E\x0E\x0E\x0E\x0E\x0E\x0E\x0E\x0E\x0E\x0E\x0E\x0E\x0E\x0E\x0E\x0E\x0E\x0E\x0E\x0E\x0E\x0E\x0E\x0E\x0E\x0E\x0E\x0E,1281499095128:
memstore size 1.0g is >= than blocking 1.0g size
2010-08-11 03:59:16,853 INFO org.apache.hadoop.hbase.regionserver.HRegion:
Blocking updates for 'IPC Server handler 24 on 60020' on region
2__HB_NOINC_GRID_0809-THREEGPPSPEECHCALLS-1281499094297,\x0E\x0E\x0E\x0E\x0E\x0E\x0E\x0E\x0E\x0E\x0E\x0E\x0E\x0E\x0E\x0E\x0E\x0E\x0E\x0E\x0E\x0E\x0E\x0E\x0E\x0E\x0E\x0E\x0E\x0E\x0E\x0E,1281499095128:
memstore size 1.0g is >= than blocking 1.0g size
2010-08-11 03:59:44,524 FATAL
org.apache.hadoop.hbase.regionserver.HRegionServer: OutOfMemoryError,
aborting.
java.lang.OutOfMemoryError: Java heap space
        at java.nio.HeapByteBuffer.<init>(HeapByteBuffer.java:39)
        at java.nio.ByteBuffer.allocate(ByteBuffer.java:312)        at
org.apache.hadoop.hbase.ipc.HBaseServer$Connection.readAndProcess(HBaseServer.java:825)
at
org.apache.hadoop.hbase.ipc.HBaseServer$Listener.doRead(HBaseServer.java:419)
at
org.apache.hadoop.hbase.ipc.HBaseServer$Listener.run(HBaseServer.java:318)
2010-08-11 03:59:44,525 INFO
org.apache.hadoop.hbase.regionserver.HRegionServer: Dump of metrics:
request=0.0, regions=9, stores=22, storefiles=4, storefileIndexSize=5,
memstoreSize=1502, compactionQueueSize=0, usedHeap=*3929*, maxHeap=3973,
blockCacheSize=6836104, blockCacheFree=826362424, blockCacheCount=0,
blockCacheHitRatio=0, fsReadLatency=0, fsWriteLatency=0, fsSyncLatency=0

Among the other RS, the highest usedHeap is 1750

On Sat, Jul 31, 2010 at 3:31 PM, Ryan Rawson <ryanobjc@gmail.com> wrote:

> Hi,
>
> #3 is going to be tricky... due to the ebb And flow of the gc this value
> isn't as accurate as one would wish. Furthermore we flush nematodes based
> on
> ram pressure.
>
> Any algorithm would have to have the property of being stable and
> conservative... rebalancing is not a 0 impact operation.
>
> There are jiras open for the rebalance based on load. To date it hasn't
> been
> a practical problem here at SU in our prod clusters however.
>
> On Jul 31, 2010 3:18 PM, "Ted Yu" <yuzhihong@gmail.com> wrote:
> > Hi,
> > Currently load balancing only considers region count.
> > See ServerManager.getAverageLoad()
> >
> > I think load balancing should consider the following three factors for
> each
> > RS:
> > 1. number of regions it hosts
> > 2. number of requests it serves within given period
> > 3. how close usedHeap is to maxHeap
> >
> > Please comment how we should weigh the above three factors in deciding
> the
> > regions to offload from each RS.
> >
> > Thanks
>

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