Just shooting from the hip here. Zookeeper maxclientcxns in zoo.cfg should be increased from the default to something like 100. Check the zookeeper log file to see if it is shutting down connections.
Check your what your max open files setting is for your OS with 'ulimit -n' and increase it if necessary. Sent from my iPhone On Aug 16, 2012, at 4:00 AM, Arjumand Bonhomme <[email protected]> wrote: Hello, I'm fairly new to both Accumulo and Hadoop, so I think my problem may be due to poor configuration on my part, but I'm running out of ideas. I'm running this on a mac laptop, with hadoop (hadoop-0.20.2 from cdh3u4) in pseudo-distributed mode. zookeeper version zookeeper-3.3.5 from cdh3u4 I'm using the 1.4.1 release of accumulo with a configuration copied from "conf/examples/512MB/standalone" I've got a Map task that is using an accumulo table as the input. I'm fetching all rows, but just a single column family, that has hundreds or even thousands of different column qualifiers. The table has a SummingCombiner installed for the given the column family. The task runs fine at first, but after ~9-15K records (I print the record count to the console every 1K records), it hangs and the following messages are printed to the console where I'm running the job: 12/08/16 02:57:08 INFO zookeeper.ClientCnxn: Unable to read additional data from server sessionid 0x1392cc35b460d1c, likely server has closed socket, closing socket connection and attempting reconnect 12/08/16 02:57:08 INFO zookeeper.ClientCnxn: Opening socket connection to server localhost/fe80:0:0:0:0:0:0:1%1:2181 12/08/16 02:57:08 INFO zookeeper.ClientCnxn: Socket connection established to localhost/fe80:0:0:0:0:0:0:1%1:2181, initiating session 12/08/16 02:57:08 INFO zookeeper.ClientCnxn: Unable to reconnect to ZooKeeper service, session 0x1392cc35b460d1c has expired, closing socket connection 12/08/16 02:57:08 INFO zookeeper.ClientCnxn: EventThread shut down 12/08/16 02:57:10 INFO zookeeper.ZooKeeper: Initiating client connection, connectString=localhost sessionTimeout=30000 watcher=org.apache.accumulo.core.zookeeper.ZooSession$AccumuloWatcher@32f5c51c 12/08/16 02:57:10 INFO zookeeper.ClientCnxn: Opening socket connection to server localhost/0:0:0:0:0:0:0:1:2181 12/08/16 02:57:10 INFO zookeeper.ClientCnxn: Socket connection established to localhost/0:0:0:0:0:0:0:1:2181, initiating session 12/08/16 02:57:10 INFO zookeeper.ClientCnxn: Session establishment complete on server localhost/0:0:0:0:0:0:0:1:2181, sessionid = 0x1392cc35b460d25, negotiated timeout = 30000 12/08/16 02:57:11 INFO mapred.LocalJobRunner: 12/08/16 02:57:14 INFO mapred.LocalJobRunner: 12/08/16 02:57:17 INFO mapred.LocalJobRunner: Sometimes the messages contain a stacktrace like this below: 12/08/16 01:57:40 WARN zookeeper.ClientCnxn: Session 0x1392cc35b460b40 for server localhost/fe80:0:0:0:0:0:0:1%1:2181, unexpected error, closing socket connection and attempting reconnect java.io.IOException: Connection reset by peer at sun.nio.ch.FileDispatcher.read0(Native Method) at sun.nio.ch.SocketDispatcher.read(SocketDispatcher.java:21) at sun.nio.ch.IOUtil.readIntoNativeBuffer(IOUtil.java:198) at sun.nio.ch.IOUtil.read(IOUtil.java:166) at sun.nio.ch.SocketChannelImpl.read(SocketChannelImpl.java:245) at org.apache.zookeeper.ClientCnxn$SendThread.doIO(ClientCnxn.java:856) at org.apache.zookeeper.ClientCnxn$SendThread.run(ClientCnxn.java:1154) 12/08/16 01:57:40 INFO zookeeper.ClientCnxn: Opening socket connection to server localhost/127.0.0.1:2181 12/08/16 01:57:40 INFO zookeeper.ClientCnxn: Socket connection established to localhost/127.0.0.1:2181, initiating session 12/08/16 01:57:40 INFO zookeeper.ClientCnxn: Unable to reconnect to ZooKeeper service, session 0x1392cc35b460b40 has expired, closing socket connection 12/08/16 01:57:40 INFO zookeeper.ClientCnxn: EventThread shut down 12/08/16 01:57:41 INFO zookeeper.ZooKeeper: Initiating client connection, connectString=localhost sessionTimeout=30000 watcher=org.apache.accumulo.core.zookeeper.ZooSession$AccumuloWatcher@684a26e8 12/08/16 01:57:41 INFO zookeeper.ClientCnxn: Opening socket connection to server localhost/fe80:0:0:0:0:0:0:1%1:2181 12/08/16 01:57:41 INFO zookeeper.ClientCnxn: Socket connection established to localhost/fe80:0:0:0:0:0:0:1%1:2181, initiating session 12/08/16 01:57:41 INFO zookeeper.ClientCnxn: Session establishment complete on server localhost/fe80:0:0:0:0:0:0:1%1:2181, sessionid = 0x1392cc35b460b46, negotiated timeout = 30000 I've poked through the logs in accumulo, and I've noticed that when it hangs, the following is written to the "logger_HOSTNAME.debug.log" file: 16 03:29:46,332 [logger.LogService] DEBUG: event null None Disconnected 16 03:29:47,248 [zookeeper.ZooSession] DEBUG: Session expired, state of current session : Expired 16 03:29:47,248 [logger.LogService] DEBUG: event null None Expired 16 03:29:47,249 [logger.LogService] WARN : Logger lost zookeeper registration at null 16 03:29:47,452 [logger.LogService] INFO : Logger shutting down 16 03:29:47,453 [logger.LogWriter] INFO : Shutting down I've noticed that if I make the map task print out the record count more frequently (ie every 10 records), it seems to be able get through more records than when I only print every 1K records. My assumption was that this had something to do with more time being spent in the map task, and not fetching data from accumulo. There was at least one occasion where I printed to the console for every record, and in that situation it managed to process 47K records, although I have been unable to repeat that behavior. I've also noticed that if I stop and start accumulo, the map-reduce job will pickup where it left off, but seems to fail quicker. Could someone make some suggestions as to what my problem might be? It would be greatly appreciated. If you need any additional information from me, just let me know. I'd paste my config files, driver setup, and example data into this post, but I think it's probably long enough already. Thanks in advance, -Arjumand
