Hi Guys I'm continuing running the test case with a 1GB data file which
contains 600000 users and 2000000 items, all the jobs are running in a 2 two
nodes cluster, each node has 32GB RAM and 8 core CPU, the RecommenderJob
running until it reach RowSimilarityJob-Mapper-EntriesToVectorsReducer Job, see
below for the error log: 11/10/18 23:09:34 INFO mapred.JobClient: map 11%
reduce 1%
11/10/18 23:12:46 INFO mapred.JobClient: map 11% reduce 2%
11/10/18 23:13:55 INFO mapred.JobClient: map 12% reduce 2%
11/10/18 23:18:22 INFO mapred.JobClient: map 13% reduce 2%
11/10/18 23:22:50 INFO mapred.JobClient: map 14% reduce 2%
11/10/18 23:27:08 INFO mapred.JobClient: map 15% reduce 2%
11/10/18 23:28:15 INFO mapred.JobClient: map 15% reduce 3%
11/10/18 23:31:42 INFO mapred.JobClient: map 16% reduce 3%
11/10/18 23:33:36 INFO mapred.JobClient: Task Id :
attempt_201110181002_0007_r_000000_0, Status : FAILED
java.io.IOException: Task: attempt_201110181002_0007_r_000000_0 - The reduce
copier failed
at org.apache.hadoop.mapred.ReduceTask.run(ReduceTask.java:380)
at org.apache.hadoop.mapred.Child.main(Child.java:170)
Caused by: java.io.IOException: Intermediate merge failed
at
org.apache.hadoop.mapred.ReduceTask$ReduceCopier$InMemFSMergeThread.doInMemMerge(ReduceTask.java:2576)
at
org.apache.hadoop.mapred.ReduceTask$ReduceCopier$InMemFSMergeThread.run(ReduceTask.java:2501)
Caused by: java.lang.RuntimeException: java.io.EOFException
at org.apache.hadoop.io.WritableComparator.compare(WritableComparator.java:103)
at org.apache.hadoop.mapred.Merger$MergeQueue.lessThan(Merger.java:373)
at org.apache.hadoop.util.PriorityQueue.upHeap(PriorityQueue.java:123)
at org.apache.hadoop.util.PriorityQueue.put(PriorityQueue.java:50)
at org.apache.hadoop.mapred.Merger$MergeQueue.merge(Merger.java:447)
at org.apache.hadoop.mapred.Merger$MergeQueue.merge(Merger.java:381)
at org.apache.hadoop.mapred.Merger.merge(Merger.java:107)
at org.apache.hadoop.mapred.Merger.merge(Merger.java:93)
at
org.apache.hadoop.mapred.ReduceTask$ReduceCopier$InMemFSMergeThread.doInMemMerge(ReduceTask.java:2551)
... 1 more
Caused by: java.io.EOFException
at java.io.DataInputStream.readByte(DataInputStream.java:250)
at org.apache.mahout.math.Varint.readUnsignedVarInt(Varint.java:159)
at org.apache.mahout.math.Varint.readSignedVarInt(Varint.java:140)
at
org.apache.mahout.math.hadoop.similarity.SimilarityMatrixEntryKey.readFields(SimilarityMatrixEntryKey.java:64)
at org.apache.hadoop.io.WritableComparator.compare(WritableComparator.java:97)
... 9 more11/10/18 23:33:37 INFO mapred.JobClient: map 16% reduce 0%
11/10/18 23:35:57 INFO mapred.JobClient: map 17% reduce 0% I googled a lot and
find i should increase "mapred.reduce.tasks" property in Hadoop, so I set it to
8 in my environment and restart this Job only, so far so good, the job is still
running by now, but it's still a little slow, so here comes my questions: 1)
does it be so slow for this job RowSimilarityJob-Mapper-EntriesToVectorsReducer
Job ?2) what does this property "mapred.reduce.tasks" do? And why it can effect
RowSimilarityJob-Mapper-EntriesToVectorsReducer Job ? (Maybe i should ask this
2nd question in hadoop user list... but i think people here are both pro at
hadoop :) )3) what can i do to increase the speed for this job? Any ideas?
Thanks in advance! Ramon
