Thankyou.. I've some more questions I'm spending quite a bit over last few weeks to develop one of our applications using HBase/Hadoop & using 0.20.4
Hbase - Table X rows - 1- 100 -> Region A -> RegionServer A --> DataNode A .... rows 1500 - 1600 -> Region M -> RegionServer B -> DataNode B So based on what I have read so far..I'm thinking of Region Server A & Data Node A pairs on the same host to make use of locality.. As per your answer ..If we restart the cluster, because of radom assigment, locality is gone so..Region Server B -..> Region A ---> data blocks will be in Data Node A ...if I understand correctly.. will the data move over time though...for example if i have lots of access to data in DataNode A ? without the current work that is in progress.. thanks again for your reply venkatesh -----Original Message----- From: Jean-Daniel Cryans <[email protected]> To: [email protected] Sent: Thu, Jul 8, 2010 1:35 pm Subject: Re: HBase on same boxes as HDFS Data nodes Former, " Now imagine you stop HBase after saving a lot of data and restarting it subsequently. The region servers are restarted and assign a seemingly random number of regions" It's not really because we enjoy it that way, but because the work required just isn't done. If this is of interest to you, Jonathan and Karthik at Facebook started rewriting our load balancer. See https://issues.apache.org/jira/browse/HBASE-2699 and https://issues.apache.org/jira/browse/HBASE-2480 J-D On Thu, Jul 8, 2010 at 10:30 AM, <[email protected]> wrote: > > Hi > Fairly new to hbase..& the list serve..Following up on this thread & the article.. > Could some one elaborate why locality is lost upon restart? Is it because > of random assignment by HMaster and/or HRegionServer is stateless or other reasons? > > thanks > venkatesh > > > > > > > > > > > -----Original Message----- > From: Jean-Daniel Cryans <[email protected]> > To: [email protected] > Sent: Thu, Jul 8, 2010 1:11 pm > Subject: Re: HBase on same boxes as HDFS Data nodes > > > More info on this blog post: > > http://www.larsgeorge.com/2010/05/hbase-file-locality-in-hdfs.html > > > > J-D > > > > On Thu, Jul 8, 2010 at 10:11 AM, Jean-Daniel Cryans <[email protected]> wrote: > >> This would be done at the expense of network IO, since you will lose > >> locality for jobs that read/write to HBase. Also I guess the datanodes > >> are also there, so HBase will lose locality with HDFS. > >> > >> J-D > >> > >> On Thu, Jul 8, 2010 at 10:07 AM, Jamie Cockrill > >> <[email protected]> wrote: > >>> Thanks all for your help with this, everything seems much more stable > >>> for the meantime. I have a backlog loading job to run over a great > >>> deal of data, so I might separate out my region servers from my task > >>> trackers for the meantime. > >>> > >>> Thanks again, > >>> > >>> Jamie > >>> > >>> > >>> > >>> On 8 July 2010 17:46, Jean-Daniel Cryans <[email protected]> wrote: > >>>> OS cache is good, glad you figured out your memory problem. > >>>> > >>>> J-D > >>>> > >>>> On Thu, Jul 8, 2010 at 2:03 AM, Jamie Cockrill <[email protected]> > > wrote: > >>>>> Morning all. Day 2 begins... > >>>>> > >>>>> I discussed this with someone else earlier and they pointed out that > >>>>> we also have task trackers running on all of those nodes, which will > >>>>> affect the amount of memory being used when jobs are being run. Each > >>>>> tasktracker had a maximum of 8 maps and 8 reduces configured per node, > >>>>> with a JVM Xmx of 512mb each. Clearly this implies a fully utilised > >>>>> node will use 8*512mb + 8*512mb = 8GB of memory on tasks alone. That's > >>>>> before the datanode does anything, or HBase for that matter. > >>>>> > >>>>> As such, I've dropped it to 4 maps, 4 reduces per node and reduced the > >>>>> Xmx to 256mb, giving a potential maximum task overhead of 2GB per > >>>>> node. Running 'vmstat 20' now, under load from mapreduce jobs, > >>>>> suggests that the actual free memory is about the same, but the memory > >>>>> cache is much much bigger, which presumably is healthlier as, in > >>>>> theory, that ought to relinquish memory to processes that request it. > >>>>> > >>>>> Lets see if that does the trick! > >>>>> > >>>>> ta > >>>>> > >>>>> Jamie > >>>>> > >>>>> > >>>>> On 7 July 2010 19:30, Jean-Daniel Cryans <[email protected]> wrote: > >>>>>> YouAreDead means that the region server's session was expired, GC > >>>>>> seems like your major problem. (file problems can happen after a GC > >>>>>> sleep because they were moved around while the process was sleeping, > >>>>>> you also get the same kind of messages with xcievers issue... sorry > >>>>>> for the confusion) > >>>>>> > >>>>>> By over committing the memory I meant trying to fit too much stuff in > >>>>>> the amount of RAM that you have. I guess it's the map and reduce tasks > >>>>>> that eat all the free space? Why not lower their number? > >>>>>> > >>>>>> J-D > >>>>>> > >>>>>> On Wed, Jul 7, 2010 at 11:22 AM, Jamie Cockrill > >>>>>> <[email protected]> wrote: > >>>>>>> PS, I've now reset my MAX_FILESIZE back to the default. (from the 1GB > >>>>>>> i raised it to). It caused me to run into a delightful > >>>>>>> 'YouAreDeadException' which looks very related to the Garbage > >>>>>>> collection issues on the Troubleshooting page, as my Zookeeper session > >>>>>>> expired. > >>>>>>> > >>>>>>> Thanks > >>>>>>> > >>>>>>> Jamie > >>>>>>> > >>>>>>> > >>>>>>> > >>>>>>> On 7 July 2010 19:19, Jamie Cockrill <[email protected]> wrote: > >>>>>>>> By overcommit, do you mean make my overcommit_ratio higher on each box > >>>>>>>> (its at the default 50 at the moment)? What I'm noticing at the moment > >>>>>>>> is that hadoop is taking up the vast majority of the memory on the > >>>>>>>> boxes. > >>>>>>>> > >>>>>>>> I found this article: > >>>>>>>> http://blog.rapleaf.com/dev/2010/01/05/the-wrath-of-drwho-or-unpredictable-hadoop-memory-usage/ > >>>>>>>> which Todd, it looks like you replied to. Does this sound like a > >>>>>>>> similar problem? No worries if you can't remember, it was back in > >>>>>>>> january! This article suggests reducing the amount of memory allocated > >>>>>>>> to Hadoop at startup, how would I go about doing this? > >>>>>>>> > >>>>>>>> Thank you everyone for your patience so far. Sorry if this is taking > >>>>>>>> up a lot of your time. > >>>>>>>> > >>>>>>>> Thanks, > >>>>>>>> > >>>>>>>> Jamie > >>>>>>>> > >>>>>>>> On 7 July 2010 19:03, Jean-Daniel Cryans <[email protected]> wrote: > >>>>>>>>> swappinness at 0 is good, but also don't overcommit your memory! > >>>>>>>>> > >>>>>>>>> J-D > >>>>>>>>> > >>>>>>>>> On Wed, Jul 7, 2010 at 10:53 AM, Jamie Cockrill > >>>>>>>>> <[email protected]> wrote: > >>>>>>>>>> I think you're right. > >>>>>>>>>> > >>>>>>>>>> Unfortunately the machines are on a separate network to this laptop, > >>>>>>>>>> so I'm having to type everything across, apologies if it doesn't > >>>>>>>>>> translate well... > >>>>>>>>>> > >>>>>>>>>> free -m gave: > >>>>>>>>>> > >>>>>>>>>> Mem Total Used Free > >>>>>>>>>> 7992 7939 53 > >>>>>>>>>> b/c 7877 114 > >>>>>>>>>> Swap: 23415 895 22519 > >>>>>>>>>> > >>>>>>>>>> I did this on another node that isn't being smashed at the moment and > >>>>>>>>>> the numbers came out similar, but the buffers/cache free was higher > >>>>>>>>>> > >>>>>>>>>> vmstat -20 is giving non-zero si and so's ranging between 3 and just > >>>>>>>>>> short of 5000. > >>>>>>>>>> > >>>>>>>>>> That seems to be it I guess. Hadoop troubleshooting suggests setting > >>>>>>>>>> swappiness to 0, is that just a case of changing the value in > >>>>>>>>>> /proc/sys/vm/swappiness? > >>>>>>>>>> > >>>>>>>>>> thanks > >>>>>>>>>> > >>>>>>>>>> Jamie > >>>>>>>>>> > >>>>>>>>>> > >>>>>>>>>> > >>>>>>>>>> > >>>>>>>>>> On 7 July 2010 18:40, Todd Lipcon <[email protected]> wrote: > >>>>>>>>>>> On Wed, Jul 7, 2010 at 10:32 AM, Jamie Cockrill >>>>>>>>>>> <[email protected]>wrote: > >>>>>>>>>>> > >>>>>>>>>>>> On the subject of GC and heap, I've left those as defaults. I could > >>>>>>>>>>>> look at those if that's the next logical step? Would there be > > anything > >>>>>>>>>>>> in any of the logs that I should look at? > >>>>>>>>>>>> > >>>>>>>>>>>> One thing I have noticed is that it does take an absolute age to log > >>>>>>>>>>>> in to the DN/RS to restart the RS once it's fallen over, in one > >>>>>>>>>>>> instance it took about 10 minutes. These are 8GB, 4 core amd64 boxes > >>>>>>>>>>>> > >>>>>>>>>>>> > >>>>>>>>>>> That indicates swapping. Can you run "free -m" on the node? > >>>>>>>>>>> > >>>>>>>>>>> Also let "vmstat 20" run while running your job and observe the "si" > > and > >>>>>>>>>>> "so" columns. If those are nonzero, it indicates you're swapping, and > > you've > >>>>>>>>>>> oversubscribed your RAM (very easy on 8G machines) > >>>>>>>>>>> > >>>>>>>>>>> -Todd > >>>>>>>>>>> > >>>>>>>>>>> > >>>>>>>>>>> > >>>>>>>>>>>> ta > >>>>>>>>>>>> > >>>>>>>>>>>> Jamie > >>>>>>>>>>>> > >>>>>>>>>>>> > >>>>>>>>>>>> > >>>>>>>>>>>> On 7 July 2010 18:30, Jamie Cockrill <[email protected]> > > wrote: > >>>>>>>>>>>> > Bad news, it looks like my xcievers is set as it should be, it's > > in > >>>>>>>>>>>> > the hdfs-site.xml and looking at the job.xml of one of my jobs in > > the > >>>>>>>>>>>> > job-tracker, it's showing that property as set to 2047. I've cat | > >>>>>>>>>>>> > grepped one of the datanode logs and although there were a few in > >>>>>>>>>>>> > there, they were from a few months ago. I've upped my MAX_FILESIZE > > on > >>>>>>>>>>>> > my table to 1GB to see if that helps (not sure if it will!). > >>>>>>>>>>>> > > >>>>>>>>>>>> > Thanks, > >>>>>>>>>>>> > > >>>>>>>>>>>> > Jamie > >>>>>>>>>>>> > > >>>>>>>>>>>> > On 7 July 2010 18:12, Jean-Daniel Cryans <[email protected]> > > wrote: > >>>>>>>>>>>> >> xcievers exceptions will be in the datanodes' logs, and your > > problem > >>>>>>>>>>>> >> totally looks like it. 0.20.5 will have the same issue (since > > it's on > >>>>>>>>>>>> >> the HDFS side) > >>>>>>>>>>>> >> > >>>>>>>>>>>> >> J-D > >>>>>>>>>>>> >> > >>>>>>>>>>>> >> On Wed, Jul 7, 2010 at 10:08 AM, Jamie Cockrill > >>>>>>>>>>>> >> <[email protected]> wrote: > >>>>>>>>>>>> >>> Hi Todd & JD, > >>>>>>>>>>>> >>> > >>>>>>>>>>>> >>> Environment: > >>>>>>>>>>>> >>> All (hadoop and HBase) installed as of karmic-cdh3, which means: > >>>>>>>>>>>> >>> Hadoop 0.20.2+228 > >>>>>>>>>>>> >>> HBase 0.89.20100621+17 > >>>>>>>>>>>> >>> Zookeeper 3.3.1+7 > >>>>>>>>>>>> >>> > >>>>>>>>>>>> >>> Unfortunately my whole cluster of regionservers have now > > crashed, so I > >>>>>>>>>>>> >>> can't really say if it was swapping too much. There is a DEBUG > >>>>>>>>>>>> >>> statement just before it crashes saying: > >>>>>>>>>>>> >>> > >>>>>>>>>>>> >>> org.apache.hadoop.hbase.regionserver.wal.HLog: closing hlog > > writer in > >>>>>>>>>>>> >>> hdfs://<somewhere on my HDFS, in /hbase> > >>>>>>>>>>>> >>> > >>>>>>>>>>>> >>> What follows is: > >>>>>>>>>>>> >>> > >>>>>>>>>>>> >>> WARN org.apache.hadoop.hdfs.DFSClient: DataStreamer Exception: > >>>>>>>>>>>> >>> org.apache.hadoop.ipc.RemoteException: > >>>>>>>>>>>> >>> org.apache.hadoop.hdfs.server.namenode.LeaseExpiredException: No > > lease > >>>>>>>>>>>> >>> on <file location as above> File does not exist. Holder > >>>>>>>>>>>> >>> DFSClient_-11113603 does not have any open files > >>>>>>>>>>>> >>> > >>>>>>>>>>>> >>> It then seems to try and do some error recovery (Error Recovery > > for > >>>>>>>>>>>> >>> block null bad datanode[0] nodes == null), fails (Could not get > > block > >>>>>>>>>>>> >>> locations. Source file "<hbase file as before>" - Aborting). > > There is > >>>>>>>>>>>> >>> then an ERROR org.apache...HRegionServer: Close and delete > > failed. > >>>>>>>>>>>> >>> There is then a similar LeaseExpiredException as above. > >>>>>>>>>>>> >>> > >>>>>>>>>>>> >>> There are then a couple of messages from HRegionServer saying > > that > >>>>>>>>>>>> >>> it's notifying master of its shutdown and stopping itself. The > >>>>>>>>>>>> >>> shutdown hook then fires and the RemoteException and > >>>>>>>>>>>> >>> LeaseExpiredExceptions are printed again. > >>>>>>>>>>>> >>> > >>>>>>>>>>>> >>> ulimit is set to 65000 (it's in the regionserver log, printed as > > I > >>>>>>>>>>>> >>> restarted the regionserver), however I haven't got the xceivers > > set > >>>>>>>>>>>> >>> anywhere. I'll give that a go. It does seem very odd as I did > > have a > >>>>>>>>>>>> >>> few of them fall over one at a time with a few early loads, but > > that > >>>>>>>>>>>> >>> seemed to be because the regions weren't splitting properly, so > > all > >>>>>>>>>>>> >>> the traffic was going to one node and it was being overwhelmed. > > Once I > >>>>>>>>>>>> >>> throttled it, after one load it a region split seemed to get > >>>>>>>>>>>> >>> triggered, which flung regions all over, which made subsequent > > loads > >>>>>>>>>>>> >>> much more distributed. However, perhaps the time-bomb was > > ticking... > >>>>>>>>>>>> >>> I'll have a go at specifying the xcievers property. I'm pretty > >>>>>>>>>>>> >>> certain i've got everything else covered, except the patches as > >>>>>>>>>>>> >>> referenced in the JIRA. > >>>>>>>>>>>> >>> > >>>>>>>>>>>> >>> I just grepped some of the log files and didn't get an explicit > >>>>>>>>>>>> >>> exception with 'xciever' in it. > >>>>>>>>>>>> >>> > >>>>>>>>>>>> >>> I am considering downgrading(?) to 0.20.5, however because > > everything > >>>>>>>>>>>> >>> is installed as per karmic-cdh3, I'm a bit reluctant to do so as > >>>>>>>>>>>> >>> presumably Cloudera has tested each of these versions against > > each > >>>>>>>>>>>> >>> other? And I don't really want to introduce further versioning > > issues. > >>>>>>>>>>>> >>> > >>>>>>>>>>>> >>> Thanks, > >>>>>>>>>>>> >>> > >>>>>>>>>>>> >>> Jamie > >>>>>>>>>>>> >>> > >>>>>>>>>>>> >>> > >>>>>>>>>>>> >>> On 7 July 2010 17:30, Jean-Daniel Cryans <[email protected]> > > wrote: > >>>>>>>>>>>> >>>> Jamie, > >>>>>>>>>>>> >>>> > >>>>>>>>>>>> >>>> Does your configuration meets the requirements? > >>>>>>>>>>>> >>>> > >>>>>>>>>>>> http://hbase.apache.org/docs/r0.20.5/api/overview-summary.html#requirements > >>>>>>>>>>>> >>>> > >>>>>>>>>>>> >>>> ulimit and xcievers, if not set, are usually time bombs that > > blow off > >>>>>>>>>>>> when > >>>>>>>>>>>> >>>> the cluster is under load. > >>>>>>>>>>>> >>>> > >>>>>>>>>>>> >>>> J-D > >>>>>>>>>>>> >>>> > >>>>>>>>>>>> >>>> On Wed, Jul 7, 2010 at 9:11 AM, Jamie Cockrill < > >>>>>>>>>>>> [email protected]>wrote: > >>>>>>>>>>>> >>>> > >>>>>>>>>>>> >>>>> Dear all, > >>>>>>>>>>>> >>>>> > >>>>>>>>>>>> >>>>> My current HBase/Hadoop architecture has HBase region servers > > on the > >>>>>>>>>>>> >>>>> same physical boxes as the HDFS data-nodes. I'm getting an > > awful lot > >>>>>>>>>>>> >>>>> of region server crashes. The last thing that happens appears > > to be a > >>>>>>>>>>>> >>>>> DroppedSnapshot Exception, caused by an IOException: could not > >>>>>>>>>>>> >>>>> complete write to file <file on HDFS>. I am running it under > > load, > >>>>>>>>>>>> how > >>>>>>>>>>>> >>>>> heavy that is I'm not sure how that is quantified, but I'm > > guessing > >>>>>>>>>>>> it > >>>>>>>>>>>> >>>>> is a load issue. > >>>>>>>>>>>> >>>>> > >>>>>>>>>>>> >>>>> Is it common practice to put region servers on data-nodes? Is > > it > >>>>>>>>>>>> >>>>> common to see region server crashes when either the HDFS or > > region > >>>>>>>>>>>> >>>>> server (or both) is under heavy load? I'm guessing that is the > > case > >>>>>>>>>>>> as > >>>>>>>>>>>> >>>>> I've seen a few similar posts. I've not got a great deal of > > capacity > >>>>>>>>>>>> >>>>> to be separating region servers from HDFS data nodes, but it > > might be > >>>>>>>>>>>> >>>>> an argument I could make. > >>>>>>>>>>>> >>>>> > >>>>>>>>>>>> >>>>> Thanks > >>>>>>>>>>>> >>>>> > >>>>>>>>>>>> >>>>> Jamie > >>>>>>>>>>>> >>>>> > >>>>>>>>>>>> >>>> > >>>>>>>>>>>> >>> > >>>>>>>>>>>> >> > >>>>>>>>>>>> > > >>>>>>>>>>>> > >>>>>>>>>>> > >>>>>>>>>>> > >>>>>>>>>>> > >>>>>>>>>>> -- > >>>>>>>>>>> Todd Lipcon > >>>>>>>>>>> Software Engineer, Cloudera > >>>>>>>>>>> > >>>>>>>>>> > >>>>>>>>> > >>>>>>>> > >>>>>>> > >>>>>> > >>>>> > >>>> > >>> > >> > > > >
