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From "Ted Yu (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HBASE-2506) Too easy to OOME a RS
Date Sun, 28 Nov 2010 06:07:38 GMT

    [ https://issues.apache.org/jira/browse/HBASE-2506?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12964499#action_12964499
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Ted Yu commented on HBASE-2506:
-------------------------------

Currently load balancer defines server load by adding number of regions.

Another definition of server load can be the summation of number of (write) accesses in the
last N minutes for each region hosted by the server. HRegionInfo can use a rolling buffer
of length N to record the number of accesses in each minute.
Under this definition, load balancer gives low weight to regions that are rarely accessed
in the near past and tries to balance 'hot' regions.

> Too easy to OOME a RS
> ---------------------
>
>                 Key: HBASE-2506
>                 URL: https://issues.apache.org/jira/browse/HBASE-2506
>             Project: HBase
>          Issue Type: Bug
>            Reporter: Jean-Daniel Cryans
>            Priority: Blocker
>             Fix For: 0.92.0
>
>
> Testing a cluster with 1GB heap, I found that we are letting the region servers kill
themselves too easily when scanning using pre-fetching. To reproduce, get 10-20M rows using
PE and run a count in the shell using CACHE => 30000 or any other very high number. For
good measure, here's the stack trace:
> {code}
> 2010-04-30 13:20:23,241 FATAL org.apache.hadoop.hbase.regionserver.HRegionServer: OutOfMemoryError,
aborting.
> java.lang.OutOfMemoryError: Java heap space
>         at java.util.Arrays.copyOf(Arrays.java:2786)
>         at java.io.ByteArrayOutputStream.write(ByteArrayOutputStream.java:94)
>         at java.io.DataOutputStream.write(DataOutputStream.java:90)
>         at org.apache.hadoop.hbase.client.Result.writeArray(Result.java:478)
>         at org.apache.hadoop.hbase.io.HbaseObjectWritable.writeObject(HbaseObjectWritable.java:312)
>         at org.apache.hadoop.hbase.io.HbaseObjectWritable.write(HbaseObjectWritable.java:229)
>         at org.apache.hadoop.hbase.ipc.HBaseServer$Handler.run(HBaseServer.java:941)
> 2010-04-30 13:20:23,241 INFO org.apache.hadoop.hbase.regionserver.HRegionServer: Dump
of metrics: request=0.0, regions=29, stores=29, storefiles=44, storefileIndexSize=6, memstoreSize=255,
>  compactionQueueSize=0, usedHeap=926, maxHeap=987, blockCacheSize=1700064, blockCacheFree=205393696,
blockCacheCount=0, blockCacheHitRatio=0
> {code}
> I guess the same could happen with largish write buffers. We need something better than
OOME.

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