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From Gaojinchao <gaojinc...@huawei.com>
Subject Re: A question about client
Date Wed, 11 May 2011 06:52:53 GMT
Thanks. I think that gc resulted in 

It is difficult to reproduce. I find it firstly in performance test cluster.


-----邮件原件-----
发件人: Ted Yu [mailto:yuzhihong@gmail.com] 
发送时间: 2011年5月11日 10:31
收件人: user@hbase.apache.org
主题: Re: A question about client

I think the second explanation is plausible.
From
http://download.oracle.com/javase/1.4.2/docs/api/java/lang/ref/SoftReference.html
:
Soft reference objects, which are cleared at the discretion of the garbage
collector in response to memory demand.

I think we should check whether possibleRegion is null in the code below.

2011/5/10 Jean-Daniel Cryans <jdcryans@apache.org>

> Are you running a modified YCSB by any chance? Because last time I
> looked at that code it didn't share the HTables between threads and it
> looks like it's doing something like that.
>
> Looking more deeper at the code, the NoSuchElementException is thrown
> because the map is empty. This is what that code looks like:
>
>      if (!matchingRegions.isEmpty()) {
>        HRegionLocation possibleRegion =
>          matchingRegions.get(matchingRegions.lastKey());
>
> So to me it seems that the only way you would get this exception is if
> someone emptied the map between the isEmpty call and lastKey which
> shouldn't happen if HTables aren't shared.
>
> The only other way it seems it could happen, and it's a stretch, is
> that since the regions are kept in a SoftValueSortedMap then the GC
> would have removed the elements you needed exactly between those two
> lines...  Is it easy for you to recreate the issue?
>
> Thx a bunch,
>
> J-D
>
> On Mon, May 9, 2011 at 11:34 PM, Gaojinchao <gaojinchao@huawei.com> wrote:
> > Hbase version: 0.90.2 .
> > I merged patches:
> > HBASE-3773      Set ZK max connections much higher in 0.90
> > HBASE-3771      All jsp pages don't clean their HBA
> > HBASE-3783      hbase-0.90.2.jar exists in hbase root and in 'lib/'
> > HBASE-3756      Can't move META or ROOT from shell
> > HBASE-3744      createTable blocks until all regions are out of
> transition
> > HBASE-3712      HTable.close() doesn't shutdown thread pool
> > HBASE-3750      HTablePool.putTable() should call
> tableFactory.releaseHTableInterface() for discarded table
> > HBASE-3722      A lot of data is lost when name node crashed
> > HBASE-3800      If HMaster is started after NN without starting DN in
> Hbase 090.2 then HMaster is not able to start due to AlreadyCreatedException
> for /hbase/hbase.version
> > HBASE-3749      Master can't exit when open port failed
> >
> > -----邮件原件-----
> > 发件人: jdcryans@gmail.com [mailto:jdcryans@gmail.com] 代表 Jean-Daniel
> Cryans
> > 发送时间: 2011年5月10日 1:17
> > 收件人: user@hbase.apache.org
> > 主题: Re: A question about client
> >
> > TreeMap isn't concurrent and it seems it was used that way? I know you
> > guys are testing a bunch of different things at the same time so which
> > HBase version and which patches were you using when you got that?
> >
> > Thx,
> >
> > J-D
> >
> > On Mon, May 9, 2011 at 5:22 AM, Gaojinchao <gaojinchao@huawei.com>
> wrote:
> >>    I used ycsb to put data and threw exception.
> >>    Who can give me some suggestion?
> >>
> >>   Hbase Code:
> >>      // Cut the cache so that we only get the part that could contain
> >>      // regions that match our key
> >>      SoftValueSortedMap<byte[], HRegionLocation> matchingRegions =
> >>        tableLocations.headMap(row);
> >>
> >>      // if that portion of the map is empty, then we're done. otherwise,
> >>      // we need to examine the cached location to verify that it is
> >>      // a match by end key as well.
> >>      if (!matchingRegions.isEmpty()) {
> >>        HRegionLocation possibleRegion =
> >>          matchingRegions.get(matchingRegions.lastKey());
> >>
> >>    ycsb client log:
> >>
> >>    [java] begin StatusThread run
> >>     [java] java.util.NoSuchElementException
> >>     [java]     at java.util.TreeMap.key(TreeMap.java:1206)
> >>     [java]     at
> java.util.TreeMap$NavigableSubMap.lastKey(TreeMap.java:1435)
> >>     [java]     at
> org.apache.hadoop.hbase.util.SoftValueSortedMap.lastKey(SoftValueSortedMap.java:131)
> >>     [java]     at
> org.apache.hadoop.hbase.client.HConnectionManager$HConnectionImplementation.getCachedLocation(HConnectionManager.java:841)
> >>     [java]     at
> org.apache.hadoop.hbase.client.HConnectionManager$HConnectionImplementation.locateRegionInMeta(HConnectionManager.java:664)
> >>     [java]     at
> org.apache.hadoop.hbase.client.HConnectionManager$HConnectionImplementation.locateRegion(HConnectionManager.java:590)
> >>     [java]     at
> org.apache.hadoop.hbase.client.HConnectionManager$HConnectionImplementation.processBatch(HConnectionManager.java:1114)
> >>     [java]     at
> org.apache.hadoop.hbase.client.HConnectionManager$HConnectionImplementation.processBatchOfPuts(HConnectionManager.java:1234)
> >>     [java]     at
> org.apache.hadoop.hbase.client.HTable.flushCommits(HTable.java:819)
> >>     [java]     at
> org.apache.hadoop.hbase.client.HTable.doPut(HTable.java:675)
> >>     [java]     at
> org.apache.hadoop.hbase.client.HTable.put(HTable.java:665)
> >>     [java]     at com.yahoo.ycsb.db.HBaseClient.update(Unknown Source)
> >>     [java]     at com.yahoo.ycsb.db.HBaseClient.insert(Unknown Source)
> >>     [java]     at com.yahoo.ycsb.DBWrapper.insert(Unknown Source)
> >>     [java]     at com.yahoo.ycsb.workloads.MyWorkload.doInsert(Unknown
> Source)
> >>     [java]     at com.yahoo.ycsb.ClientThread.run(Unknown Source)
> >>
> >
>
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