[NUTCH-1315] reduce speculation on but ParseOutputFormat doesn't name output files correctly?

• Type: Bug
• Status: Open
• Priority: Major
• Resolution: Unresolved
• Affects Version/s: 1.4
• Component/s: parser
• Labels: hadoop hdfs

Environment

ubuntu 64bit, hadoop 1.0.1, 3 Node Cluster, segment size 1.5M urls

• Assignee: Unassigned
• Reporter: Rafael
• Created: 19/Mar/12 18:20
• Updated: 28/Aug/15 20:34

Description

From time to time the Reducer log contains the following and one tasktracker gets blacklisted.

org.apache.hadoop.ipc.RemoteException: org.apache.hadoop.hdfs.protocol.AlreadyBeingCreatedException: failed to create file /user/test/crawl/segments/20120316065507/parse_text/part-00001/data for DFSClient_attempt_201203151054_0028_r_000001_1 on client xx.x.xx.xx.10, because this file is already being created by DFSClient_attempt_201203151054_0028_r_000001_0 on xx.xx.xx.9
at org.apache.hadoop.hdfs.server.namenode.FSNamesystem.recoverLeaseInternal(FSNamesystem.java:1404)
at org.apache.hadoop.hdfs.server.namenode.FSNamesystem.startFileInternal(FSNamesystem.java:1244)
at org.apache.hadoop.hdfs.server.namenode.FSNamesystem.startFile(FSNamesystem.java:1186)
at org.apache.hadoop.hdfs.server.namenode.NameNode.create(NameNode.java:628)
at sun.reflect.GeneratedMethodAccessor8.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at org.apache.hadoop.ipc.RPC$Server.call(RPC.java:563)
at org.apache.hadoop.ipc.Server$Handler$1.run(Server.java:1388)
at org.apache.hadoop.ipc.Server$Handler$1.run(Server.java:1384)
at java.security.AccessController.doPrivileged(Native Method)
at javax.security.auth.Subject.doAs(Subject.java:396)
at org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1093)
at org.apache.hadoop.ipc.Server$Handler.run(Server.java:1382)

at org.apache.hadoop.ipc.Client.call(Client.java:1066)
at org.apache.hadoop.ipc.RPC$Invoker.invoke(RPC.java:225)
at $Proxy2.create(Unknown Source)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at org.apache.hadoop.io.retry.RetryInvocationHandler.invokeMethod(RetryInvocationHandler.java:82)
at org.apache.hadoop.io.retry.RetryInvocationHandler.invoke(RetryInvocationHandler.java:59)
at $Proxy2.create(Unknown Source)
at org.apache.hadoop.hdfs.DFSClient$DFSOutputStream.<init>(DFSClient.java:3245)
at org.apache.hadoop.hdfs.DFSClient.create(DFSClient.java:713)
at org.apache.hadoop.hdfs.DistributedFileSystem.create(DistributedFileSystem.java:182)
at org.apache.hadoop.fs.FileSystem.create(FileSystem.java:555)
at org.apache.hadoop.io.SequenceFile$RecordCompressWriter.<init>(SequenceFile.java:1132)
at org.apache.hadoop.io.SequenceFile.createWriter(SequenceFile.java:397)
at org.apache.hadoop.io.SequenceFile.createWriter(SequenceFile.java:354)
at org.apache.hadoop.io.SequenceFile.createWriter(SequenceFile.java:476)
at org.apache.hadoop.io.MapFile$Writer.<init>(MapFile.java:157)
at org.apache.hadoop.io.MapFile$Writer.<init>(MapFile.java:134)
at org.apache.hadoop.io.MapFile$Writer.<init>(MapFile.java:92)
at org.apache.nutch.parse.ParseOutputFormat.getRecordWriter(ParseOutputFormat.java:110)
at org.apache.hadoop.mapred.ReduceTask$OldTrackingRecordWriter.<init>(ReduceTask.java:448)
at org.apache.hadoop.mapred.ReduceTask.runOldReducer(ReduceTask.java:490)
at org.apache.hadoop.mapred.ReduceTask.run(ReduceTask.java:420)
at org.apache.hadoop.mapred.Child$4.run(Child.java:255)
at java.security.AccessController.doPrivileged(Native Method)
at javax.security.auth.Subject.doAs(Subject.java:396)
at org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1093)
at org.apache.hadoop.mapred.Child.main(Child.java:249)

I asked the hdfs-user mailing list and i got the following answer:

"Looks like you have reduce speculation turned on, but the
ParseOutputFormat you're using doesn't properly name its output files
distinctly based on the task attempt ID. As a workaround you can
probably turn off speculative execution for reduces, but you should
also probably file a Nutch bug."