On Thu, Sep 24, 2009 at 4:09 PM, Florian Leibert <[email protected]> wrote:
> We can't really alter the jobs... This is a rather complex system with our > own DSL for writing jobs so that other departments can use our data. The > number of mappers is determined based on the number of input files > involved... > Ok > > Setting this to 0 in a cluster where resources will be scarce at times > doesn't really sound like a solution - I don't have any of these problems > on > our 30 node test cluster, so I can't really try it out there and setting > the > timeout to 0 on production doesn't give me a great deal of confidence... > > Ok.. In that case, lets see if someone else is able to give an alternate workaround/solution to this. Write a little bit more about the kind of job, how compute intensive it is, the number of mappers (one of the cases where it troubles), the number of reducers, number of tasks per node, does the job fail or does it give this exception and carry on to restart the task and finish it, your cluster configuration etc.. That might give a better understanding of the issue. > > > On Thu, Sep 24, 2009 at 3:48 PM, Amandeep Khurana <[email protected]> > wrote: > > > On Thu, Sep 24, 2009 at 3:39 PM, Florian Leibert <[email protected]> wrote: > > > > > This happens maybe 4-5 times a day on an arbitrary node - it usually > > occurs > > > during very intense jobs where there are 10s of thousands of map tasks > > > scheduled... > > > > > > > Right.. So, the reason most probably is that the particular file being > read > > is being kept open during the computation and thats causing the timeouts. > > You can try to alter your jobs and number of tasks and see if you can > come > > out with a workaround. > > > > > > > From what I gather in the code, this results from a write attempt - the > > > selector seems to wait until it can write to a channel - setting this > to > > 0 > > > might impact our cluster reliability, hence I'm not > > > > > > > > Setting the timeout to 0 doesnt impact the cluster reliability. We have > it > > set to 0 on our clusters as well and its a pretty normal thing to do. > > However, we do it because we are using HBase as well and that is known to > > keep file handles open for long periods. But, setting the timeout to 0 > > doesnt impact any of our non-Hbase applications/jobs at all.. So, its not > a > > problem. > > > > > > > On Thu, Sep 24, 2009 at 3:16 PM, Amandeep Khurana <[email protected]> > > > wrote: > > > > > > > What were you doing when you got this error? Did you monitor the > > resource > > > > consumption during whatever you were doing? > > > > > > > > Reason I said was that sometimes, file handles are open for longer > than > > > the > > > > timeout for some reason (intended though) and that causes trouble.. > So, > > > > people keep the timeout at 0 to solve this problem. > > > > > > > > > > > > Amandeep Khurana > > > > Computer Science Graduate Student > > > > University of California, Santa Cruz > > > > > > > > > > > > On Thu, Sep 24, 2009 at 3:12 PM, Florian Leibert <[email protected]> > > wrote: > > > > > > > > > I don't think setting the timeout to 0 is a good idea - after all > we > > > have > > > > a > > > > > lot writes going on so it should happen at times that a resource > > isn't > > > > > available immediately. Am I missing something or what's your > > reasoning > > > > for > > > > > assuming that the timeout value is the problem? > > > > > > > > > > On Thu, Sep 24, 2009 at 2:19 PM, Amandeep Khurana < > [email protected]> > > > > > wrote: > > > > > > > > > > > When do you get this error? > > > > > > > > > > > > Try making the timeout to 0. That'll remove the timeout of 480s. > > > > Property > > > > > > name: dfs.datanode.socket.write.timeout > > > > > > > > > > > > -ak > > > > > > > > > > > > > > > > > > > > > > > > Amandeep Khurana > > > > > > Computer Science Graduate Student > > > > > > University of California, Santa Cruz > > > > > > > > > > > > > > > > > > On Thu, Sep 24, 2009 at 1:36 PM, Florian Leibert <[email protected] > > > > > > wrote: > > > > > > > > > > > > > Hi, > > > > > > > recently, we're seeing frequent STEs in our datanodes. We had > > prior > > > > > fixed > > > > > > > this issue by upping the handler count max.xciever (note this > is > > > > > > misspelled > > > > > > > in the code as well - so we're just being consistent). > > > > > > > We're using 0.19 with a couple of patches - none of which > should > > > > affect > > > > > > any > > > > > > > of the areas in the stacktrace. > > > > > > > > > > > > > > We've seen this before upping the limits on the xcievers - but > > > these > > > > > > > settings seem very high already. We're running 102 nodes. > > > > > > > > > > > > > > Any hints would be appreciated. > > > > > > > > > > > > > > <property> > > > > > > > <name>dfs.datanode.handler.count</name> > > > > > > > <value>300</value> > > > > > > > </property> > > > > > > > <property> > > > > > > > <name>dfs.namenode.handler.count</name> > > > > > > > <value>300</value> > > > > > > > </property> > > > > > > > <property> > > > > > > > <name>dfs.datanode.max.xcievers</name> > > > > > > > <value>2000</value> > > > > > > > </property> > > > > > > > > > > > > > > > > > > > > > 2009-09-24 17:48:13,648 ERROR > > > > > > > org.apache.hadoop.hdfs.server.datanode.DataNode: > > > > DatanodeRegistration( > > > > > > > 10.16.160.79:50010, > > > > > > > storageID=DS-1662533511-10.16.160.79-50010-1219665628349, > > > > > infoPort=50075, > > > > > > > ipcPort=50020):DataXceiver > > > > > > > java.net.SocketTimeoutException: 480000 millis timeout while > > > waiting > > > > > for > > > > > > > channel to be ready for write. ch : > > > > > > > java.nio.channels.SocketChannel[connected local=/ > > > 10.16.160.79:50010 > > > > > > remote=/ > > > > > > > 10.16.134.78:34280] > > > > > > > at > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > org.apache.hadoop.net.SocketIOWithTimeout.waitForIO(SocketIOWithTimeout.java:185) > > > > > > > at > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > org.apache.hadoop.net.SocketOutputStream.waitForWritable(SocketOutputStream.java:159) > > > > > > > at > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > org.apache.hadoop.net.SocketOutputStream.transferToFully(SocketOutputStream.java:198) > > > > > > > at > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > org.apache.hadoop.hdfs.server.datanode.BlockSender.sendChunks(BlockSender.java:293) > > > > > > > at > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > org.apache.hadoop.hdfs.server.datanode.BlockSender.sendBlock(BlockSender.java:387) > > > > > > > at > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > org.apache.hadoop.hdfs.server.datanode.DataXceiver.readBlock(DataXceiver.java:179) > > > > > > > at > > > > > > > > > > > > > > > > > > > > > > > > > > > > org.apache.hadoop.hdfs.server.datanode.DataXceiver.run(DataXceiver.java:94) > > > > > > > at java.lang.Thread.run(Thread.java:619) > > > > > > > > > > > > > > > > > > > > > > > > > > > >
