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https://issues.apache.org/jira/browse/HADOOP-5850?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12712686#action_12712686
]
Ramya R commented on HADOOP-5850:
---------------------------------
With the above fix, when a job (writing to DFS) with 0 maps and >0 reduces is
submitted, the cluster hangs completely.
The TT logs show "INFO org.apache.hadoop.mapred.TaskTracker: Resending 'status'
to <jt>' with reponseId 'ID" infinitely and the JT throws java.io.IOException:
java.lang.ArithmeticException forever.
Below is the stacktrace:
{noformat}
2009-05-25 08:13:00,124 INFO org.apache.hadoop.ipc.Server: IPC Server handler
37 on <portno>, call
heartbeat(org.apache.hadoop.mapred.tasktrackersta...@14d128c, false, false,
true, 3231) from <ip>:<port> error: java.io.IOException:
java.lang.ArithmeticException: / by zero
java.io.IOException: java.lang.ArithmeticException: / by zero
at
org.apache.hadoop.mapred.ResourceEstimator.getEstimatedMapOutputSize(ResourceEstimator.java:85)
at
org.apache.hadoop.mapred.JobInProgress.findNewMapTask(JobInProgress.java:1729)
at
org.apache.hadoop.mapred.JobInProgress.obtainNewMapTask(JobInProgress.java:978)
at
org.apache.hadoop.mapred.CapacityTaskScheduler$MapSchedulingMgr.obtainNewTask(CapacityTaskScheduler.java:572)
at
org.apache.hadoop.mapred.CapacityTaskScheduler$TaskSchedulingMgr.getTaskFromQueue(CapacityTaskScheduler.java:418)
at
org.apache.hadoop.mapred.CapacityTaskScheduler$TaskSchedulingMgr.assignTasks(CapacityTaskScheduler.java:498)
at
org.apache.hadoop.mapred.CapacityTaskScheduler$TaskSchedulingMgr.access$500(CapacityTaskScheduler.java:277)
at
org.apache.hadoop.mapred.CapacityTaskScheduler.assignTasks(CapacityTaskScheduler.java:977)
at org.apache.hadoop.mapred.JobTracker.heartbeat(JobTracker.java:2605)
at sun.reflect.GeneratedMethodAccessor7.invoke(Unknown Source)
at
sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at org.apache.hadoop.ipc.RPC$Server.call(RPC.java:508)
at org.apache.hadoop.ipc.Server$Handler$1.run(Server.java:959)
at org.apache.hadoop.ipc.Server$Handler$1.run(Server.java:955)
at java.security.AccessController.doPrivileged(Native Method)
at javax.security.auth.Subject.doAs(Subject.java:396)
at org.apache.hadoop.ipc.Server$Handler.run(Server.java:953)
{noformat}
In such a case, all the jobs hang infinitely without progressing and the
cluster is completely down.
This problem is solved only when the no-map job is killed. Once the job is
killed the cluster is back running and the other jobs proceed smoothly.
> map/reduce doesn't run jobs with 0 maps
> ---------------------------------------
>
> Key: HADOOP-5850
> URL: https://issues.apache.org/jira/browse/HADOOP-5850
> Project: Hadoop Core
> Issue Type: Bug
> Components: mapred
> Affects Versions: 0.20.0
> Reporter: Owen O'Malley
> Assignee: Vinod K V
> Priority: Critical
> Fix For: 0.20.1
>
> Attachments: HADOOP-5850-20090519.1.txt, HADOOP-5850-20090519.txt,
> HADOOP-5850-20090520-svn-branch-20.v2.txt, HADOOP-5850-20090520-svn.1.txt,
> HADOOP-5850-20090522-branch-20-final.txt, HADOOP-5850-20090522.txt,
> screenshot-1.jpg
>
>
> Currently, the framework ignores jobs that have 0 maps. This is incorrect.
> Many pipelines need the job to run (if nothing else, to create the output
> directory!) so that subsequent jobs don't fail. Effectively, there will be no
> map tasks and the reduce tasks should immediately set up the Reducer and
> RecordWriter and then call close on both since there are no inputs to the
> reduce. I believe it should just work if we remove the check...
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