Hi, all
Just to keep this topic updated :) I am still tring to figure what
happened.
I found that in my 2-node configuration (namenode and jobtracker on
node-1, while both are datanodes and tasktrackers). The reduce task may
sometimes (but rarely) complete for programs that needs small amount of
CPU time (e.g., mrbench), but for programs with large computation, it
never finish. When reduces blocks, it always fails at 16%.
Eventually I will get this error information:
08/01/18 15:01:27 WARN mapred.JobClient: Error reading task
outputncdm-IPxxxxxxxxx
08/01/18 15:01:27 WARN mapred.JobClient: Error reading task
outputncdm-IPxxxxxxxxx
08/01/18 15:13:38 INFO mapred.JobClient: Task Id :
task_200801181145_0005_r_000000_1, Status : FAILED
Shuffle Error: Exceeded MAX_FAILED_UNIQUE_FETCHES; bailing-out.
08/01/18 19:56:38 WARN mapred.JobClient: Error reading task outputConnection
timed out
08/01/18 19:59:47 WARN mapred.JobClient: Error reading task outputConnection
timed out
08/01/18 20:09:40 INFO mapred.JobClient: map 100% reduce 100%
java.io.IOException: Job failed!
I found that "IPxxxxxxxx" is not the correct network address
that Hadoop should read result from. The servers I use have 2 network
interfaces and I am using another one. I explicitly fill the IP addresses
10.0.0.x in all the configuration files.
Might this be the reason of Reduce failure? But the Map phase does work.
Thanks
Yunhong
On Sat, 19 Jan 2008, Yunhong Gu1 wrote:
Oh, so it is the task running on the other node (ncdm-15) fails and Hadoop
re-run the task on the local node (ncdm-8). (I only have two nodes, ncdm-8
and ncdm-15. Both namenode and jobtracker are running on ncdm-8. The program
is also started on ncdm-8).
08/01/18 19:08:27 INFO mapred.JobClient: Task Id :
task_200801181852_0001_m_000001_0, Status : FAILED Too many fetch-failures
08/01/18 19:08:27 WARN mapred.JobClient: Error reading task outputncdm15
Any ideas why the task would fail? And why it takes so long for Hadoop to
detect the failure?
Thanks
Yunhong
On Sat, 19 Jan 2008, Devaraj Das wrote:
Hi Yunhong,
As per the output it seems the job ran to successful completion (albeit
with
some failures)...
Devaraj
-----Original Message-----
From: Yunhong Gu1 [mailto:[EMAIL PROTECTED]
Sent: Saturday, January 19, 2008 8:56 AM
To: [EMAIL PROTECTED]
Subject: Re: Reduce hangs
Yes, it looks like HADOOP-1374
The program actually failed after a while:
[EMAIL PROTECTED]:~/hadoop-0.15.2$ ./bin/hadoop jar
hadoop-0.15.2-test.jar mrbench
MRBenchmark.0.0.2
08/01/18 18:53:08 INFO mapred.MRBench: creating control file:
1 numLines, ASCENDING sortOrder
08/01/18 18:53:08 INFO mapred.MRBench: created control file:
/benchmarks/MRBench/mr_input/input_-450753747.txt
08/01/18 18:53:09 INFO mapred.MRBench: Running job 0:
input=/benchmarks/MRBench/mr_input
output=/benchmarks/MRBench/mr_output/output_1843693325
08/01/18 18:53:09 INFO mapred.FileInputFormat: Total input
paths to process : 1
08/01/18 18:53:09 INFO mapred.JobClient: Running job:
job_200801181852_0001
08/01/18 18:53:10 INFO mapred.JobClient: map 0% reduce 0%
08/01/18 18:53:17 INFO mapred.JobClient: map 100% reduce 0%
08/01/18 18:53:25 INFO mapred.JobClient: map 100% reduce 16%
08/01/18 19:08:27 INFO mapred.JobClient: Task Id :
task_200801181852_0001_m_000001_0, Status : FAILED Too many
fetch-failures
08/01/18 19:08:27 WARN mapred.JobClient: Error reading task
outputncdm15
08/01/18 19:08:27 WARN mapred.JobClient: Error reading task
outputncdm15
08/01/18 19:08:34 INFO mapred.JobClient: map 100% reduce 100%
08/01/18 19:08:35 INFO mapred.JobClient: Job complete:
job_200801181852_0001
08/01/18 19:08:35 INFO mapred.JobClient: Counters: 10
08/01/18 19:08:35 INFO mapred.JobClient: Job Counters
08/01/18 19:08:35 INFO mapred.JobClient: Launched map tasks=3
08/01/18 19:08:35 INFO mapred.JobClient: Launched reduce tasks=1
08/01/18 19:08:35 INFO mapred.JobClient: Data-local map tasks=2
08/01/18 19:08:35 INFO mapred.JobClient: Map-Reduce Framework
08/01/18 19:08:35 INFO mapred.JobClient: Map input records=1
08/01/18 19:08:35 INFO mapred.JobClient: Map output records=1
08/01/18 19:08:35 INFO mapred.JobClient: Map input bytes=2
08/01/18 19:08:35 INFO mapred.JobClient: Map output bytes=5
08/01/18 19:08:35 INFO mapred.JobClient: Reduce input groups=1
08/01/18 19:08:35 INFO mapred.JobClient: Reduce input records=1
08/01/18 19:08:35 INFO mapred.JobClient: Reduce output records=1
DataLines Maps Reduces AvgTime (milliseconds)
1 2 1 926333
On Fri, 18 Jan 2008, Konstantin Shvachko wrote:
Looks like we still have this unsolved mysterious problem:
http://issues.apache.org/jira/browse/HADOOP-1374
Could it be related to HADOOP-1246? Arun?
Thanks,
--Konstantin
Yunhong Gu1 wrote:
Hi,
If someone knows how to fix the problem described below,
please help
me out. Thanks!
I am testing Hadoop on 2-node cluster and the "reduce"
always hangs
at some stage, even if I use different clusters. My OS is Debian
Linux kernel 2.6 (AMD Opteron w/ 4GB Mem). Hadoop verision
is 0.15.2.
Java version is 1.5.0_01-b08.
I simply tried "./bin/hadoop jar hadoop-0.15.2-test.jar
mrbench" and
when the map stage finishes, the reduce stage will hang
somewhere in
the middle, sometimes at 0%. I also tried any other
mapreduce program
I can find in the example jar package but they all hang.
The log file simply print
2008-01-18 15:15:50,831 INFO org.apache.hadoop.mapred.TaskTracker:
task_200801181424_0004_r_000000_0 0.0% reduce > copy >
2008-01-18 15:15:56,841 INFO org.apache.hadoop.mapred.TaskTracker:
task_200801181424_0004_r_000000_0 0.0% reduce > copy >
2008-01-18 15:16:02,850 INFO org.apache.hadoop.mapred.TaskTracker:
task_200801181424_0004_r_000000_0 0.0% reduce > copy >
forever.
The program does work if I start Hadoop only on single node.
Below is my hadoop-site.xml configuration:
<configuration>
<property>
<name>fs.default.name</name>
<value>10.0.0.1:60000</value>
</property>
<property>
<name>mapred.job.tracker</name>
<value>10.0.0.1:60001</value>
</property>
<property>
<name>dfs.data.dir</name>
<value>/raid/hadoop/data</value>
</property>
<property>
<name>mapred.local.dir</name>
<value>/raid/hadoop/mapred</value>
</property>
<property>
<name>hadoop.tmp.dir</name>
<value>/raid/hadoop/tmp</value>
</property>
<property>
<name>mapred.child.java.opts</name>
<value>-Xmx1024m</value>
</property>
<property>
<name>mapred.tasktracker.tasks.maximum</name>
<value>4</value>
</property>
<!--
<property>
<name>mapred.map.tasks</name>
<value>7</value>
</property>
<property>
<name>mapred.reduce.tasks</name>
<value>3</value>
</property>
-->
<property>
<name>fs.inmemory.size.mb</name>
<value>200</value>
</property>
<property>
<name>dfs.block.size</name>
<value>134217728</value>
</property>
<property>
<name>io.sort.factor</name>
<value>100</value>
</property>
<property>
<name>io.sort.mb</name>
<value>200</value>
</property>
<property>
<name>io.file.buffer.size</name>
<value>131072</value>
</property>
</configuration>
