Did you try upping it Andy? Andrew Purtell's recommendation though old would have come of experience. The Intel article reads like sales but there is probably merit to its suggestion. The Cloudera article is more unsure about the effect of upping handlers though it allows "...could be set a bit higher."
I just looked at our prod frontend and its set to 3 still. I don't see your exceptions in our DN log. What version of hadoop? You say hbase 0.91. You mean 0.90.1? ulimit and nproc are set sufficiently high for hadoop/hbase user? If you grep 163126943925471435_28809750 in namenode log, do you see a delete occur before a later open? St.Ack On Sat, Apr 9, 2011 at 4:35 PM, Andy Sautins <[email protected]> wrote: > > I ran across an mailing list posting from 1/4/2009 that seemed to indicate > increasing dfs.datanode.handler.count could help improve DFS stability > (http://mail-archives.apache.org/mod_mbox/hbase-user/200901.mbox/%[email protected]%3E > ). The posting seems to indicate the wiki was updated, but I don't seen > anything in the wiki about increasing dfs.datanode.handler.count. I have > seen a few other notes that seem to show examples that have raised > dfs.datanode.handler.count including one from an IBM article > (http://software.intel.com/en-us/articles/hadoop-and-hbase-optimization-for-read-intensive-search-applications/ > ) and the Pro Hadoop book, but other than that the only other mention I see > is from cloudera seems luke-warm on increasing dfs.datanode.handler.count > (http://www.cloudera.com/blog/2009/03/configuration-parameters-what-can-you-just-ignore/ > ). > > Given the post is from 2009 I thought I'd ask if anyone has had any > success improving stability of HBase/DFS when increasing > dfs.datanode.handler.count. The specific error we are seeing somewhat > frequently ( few hundred times per day ) in the datanode longs is as follows: > > 2011-04-09 00:12:48,035 ERROR > org.apache.hadoop.hdfs.server.datanode.DataNode: > DatanodeRegistration(10.18.0.33:50010, > storageID=DS-1501576934-10.18.0.33-50010-1296248656454, infoPort=50075, > ipcPort=50020):DataXceiver > java.io.IOException: Block blk_-163126943925471435_28809750 is not valid. > > The above seems to correspond to ClosedChannelExceptions in the hbase > regionserver logs as well as some warnings about long write to hlog ( some in > the 50+ seconds ). > > The biggest end-user facing issue we are seeing is that Task Trackers keep > getting blacklisted. It's quite possible our problem is unrelated to > anything HBase, but I thought it was worth asking given what we've been > seeing. > > We are currently running 0.91 on an 18 node cluster with ~3k total regions > and each region server is running with 2G of memory. > > Any insight would be appreciated. > > Thanks > > Andy >
