Although the reactions did not give me the feeling there was much
interest in my case, i have found a "solution" and some reasons for my
problem. You might be interested in the discussion on Stackoverflow:
http://stackoverflow.com/questions/10720132/hadoop-reducer-is-waiting-for-mapper-inputs
Am 23.05.2012 10:47, schrieb Björn-Elmar Macek:
Ok, i have look at the logs some further and googled every tiny bit of
them, hoping to find an answer out there.
I fear that the following line nails my problem at a big scale:
12/05/22 01:30:21 INFO mapred.ReduceTask:
attempt_local_0001_r_000000_0 Need another 2 map output(s)
where 0 is already in progress
I found several discussions to problems, that also had this line in
their logs. I have checked my code for the following:
* All inputs are collected in the mapper (tho not all would be neccessary)
* The Comparators run well and return proper values for all inputs
* The Partitioner always returns proper values
Please, i would really need a hint, to where i have to look.
Am 22.05.2012 16:57, schrieb Björn-Elmar Macek:
Hi Jayaseelan,
thanks for the bump! ;)
I have continued working on the problem, but with no further success.
I emptied the log directory and started the debugging all over again,
resulting in no new logfiles, so i guess the program did not run into
serious problems. Also all the code other classes, namely ...
* Mapper
* Partitioner
* OutputKeyComparatorClass
is executed and can easily be debugged. Stil the Reducer and the
OutputValueGroupingComparator do NOT work. After the execution of the
comparisons made by OutputKeyComparatorClass i get alot of active
processes in my debugging view in eclipse:
OpenJDK Client VM[localhost:5002]
Thread [main] (Running)
Thread [Thread-2] (Running)
Daemon Thread [communication thread] (Running)
Thread [MapOutputCopier attempt_local_0001_r_000000_0.0] (Running)
Daemon Thread [Thread for merging in memory files] (Running)
Thread [MapOutputCopier attempt_local_0001_r_000000_0.4] (Running)
Thread [MapOutputCopier attempt_local_0001_r_000000_0.3] (Running)
Thread [MapOutputCopier attempt_local_0001_r_000000_0.1] (Running)
Thread [MapOutputCopier attempt_local_0001_r_000000_0.2] (Running)
Daemon Thread [Thread for merging on-disk files] (Running)
Daemon Thread [Thread for polling Map Completion Events] (Running)
And those processes are running, but obviously waiting for something,
since no output is produced. And it is not due to the havy load of
input data, since this is a 10 line csv file, which shouldnt make any
problems.
I somehow have the feeling that the framework cannot handle my
classes, but i dont understand why.
I would really appreciate a decent hint, how to fix that.
Thanks you for your time and help!
Björn-Elmar
Am 22.05.2012 12:38, schrieb Jayaseelan E:
------------------------------------------------------------------------
*From:* Björn-Elmar Macek [mailto:ma...@cs.uni-kassel.de]
*Sent:* Tuesday, May 22, 2012 3:12 PM
*To:* hdfs-user@hadoop.apache.org
*Subject:* Hadoop Debugging in LocalMode (Breakpoints not reached)
Hi there,
i am currently trying to get rid of bugs in my Hadoop program by
debugging it. Everything went fine til some point yesterday. I dont
know what exactly happened, but my program does not stop at
breakpoints within the Reducer and also not within the RawComparator
for the values which i do use for sorting my inputs in the
ReducerIterator.
(see the classes set for the conf below:)
conf.setOutputValueGroupingComparator(TwitterValueGroupingComparator.class);
conf.setReducerClass(RetweetReducer.class);
The log looks like this:
Warning: $HADOOP_HOME is deprecated.
Listening for transport dt_socket at address: 5002
12/05/21 19:24:20 INFO util.NativeCodeLoader: Loaded the
native-hadoop library
12/05/21 19:24:20 WARN mapred.JobClient: Use GenericOptionsParser
for parsing the arguments. Applications should implement Tool for
the same.
12/05/21 19:24:20 WARN snappy.LoadSnappy: Snappy native library not
loaded
12/05/21 19:24:20 INFO mapred.FileInputFormat: Total input paths to
process : 2
12/05/21 19:24:20 WARN conf.Configuration:
file:/tmp/hadoop-ema/mapred/local/localRunner/job_local_0001.xml:a
attempt to override final parameter: fs.default.name;Ignoring.
12/05/21 19:24:20 WARN conf.Configuration:
file:/tmp/hadoop-ema/mapred/local/localRunner/job_local_0001.xml:a
attempt to override final parameter: mapred.job.tracker;Ignoring.
12/05/21 19:24:20 INFO mapred.JobClient: Running job: job_local_0001
12/05/21 19:24:20 INFO util.ProcessTree: setsid exited with exit code 0
12/05/21 19:24:21 INFO mapred.Task:Using ResourceCalculatorPlugin :
org.apache.hadoop.util.LinuxResourceCalculatorPlugin@1c4ff2c
12/05/21 19:24:21 INFO mapred.MapTask: numReduceTasks: 1
12/05/21 19:24:21 INFO mapred.MapTask: io.sort.mb = 100
12/05/21 19:24:22 INFO mapred.JobClient:map 0% reduce 0%
12/05/21 19:24:22 INFO mapred.MapTask: data buffer = 79691776/99614720
12/05/21 19:24:22 INFO mapred.MapTask: record buffer = 262144/327680
12/05/21 19:24:22 INFO mapred.MapTask: Starting flush of map output
12/05/21 19:24:22 INFO mapred.MapTask: Finished spill 0
12/05/21 19:24:22 INFO mapred.Task:
Task:attempt_local_0001_m_000000_0 is done. And is in the process of
commiting
12/05/21 19:24:23 INFO mapred.LocalJobRunner:
file:/home/ema/INPUT-H/tweets_ext:0+968
12/05/21 19:24:23 INFO mapred.Task: Task
'attempt_local_0001_m_000000_0' done.
12/05/21 19:24:23 INFO mapred.Task:Using ResourceCalculatorPlugin :
org.apache.hadoop.util.LinuxResourceCalculatorPlugin@1e8c585
12/05/21 19:24:23 INFO mapred.MapTask: numReduceTasks: 1
12/05/21 19:24:23 INFO mapred.MapTask: io.sort.mb = 100
12/05/21 19:24:24 INFO mapred.MapTask: data buffer = 79691776/99614720
12/05/21 19:24:24 INFO mapred.MapTask: record buffer = 262144/327680
12/05/21 19:24:24 INFO mapred.MapTask: Starting flush of map output
12/05/21 19:24:24 INFO mapred.Task:
Task:attempt_local_0001_m_000001_0 is done. And is in the process of
commiting
12/05/21 19:24:24 INFO mapred.JobClient:map 100% reduce 0%
12/05/21 19:24:26 INFO mapred.LocalJobRunner:
file:/home/ema/INPUT-H/tweets~:0+0
12/05/21 19:24:26 INFO mapred.Task: Task
'attempt_local_0001_m_000001_0' done.
12/05/21 19:24:26 INFO mapred.Task:Using ResourceCalculatorPlugin :
org.apache.hadoop.util.LinuxResourceCalculatorPlugin@191e4c
12/05/21 19:24:26 INFO mapred.ReduceTask: ShuffleRamManager:
MemoryLimit=709551680, MaxSingleShuffleLimit=177387920
12/05/21 19:24:27 INFO mapred.ReduceTask:
attempt_local_0001_r_000000_0 Need another 2 map output(s) where 0
is already in progress
12/05/21 19:24:27 INFO mapred.ReduceTask:
attempt_local_0001_r_000000_0 Thread started: Thread for merging
on-disk files
12/05/21 19:24:27 INFO mapred.ReduceTask:
attempt_local_0001_r_000000_0 Thread waiting: Thread for merging
on-disk files
12/05/21 19:24:27 INFO mapred.ReduceTask:
attempt_local_0001_r_000000_0 Scheduled 0 outputs (0 slow hosts and0
dup hosts)
12/05/21 19:24:27 INFO mapred.ReduceTask:
attempt_local_0001_r_000000_0 Thread started: Thread for merging in
memory files
12/05/21 19:24:27 INFO mapred.ReduceTask:
attempt_local_0001_r_000000_0 Thread started: Thread for polling Map
Completion Events
12/05/21 19:24:32 INFO mapred.LocalJobRunner: reduce > copy >
12/05/21 19:24:35 INFO mapred.LocalJobRunner: reduce > copy >
12/05/21 19:24:42 INFO mapred.LocalJobRunner: reduce > copy >
12/05/21 19:24:48 INFO mapred.LocalJobRunner: reduce > copy >
12/05/21 19:24:51 INFO mapred.LocalJobRunner: reduce > copy >
12/05/21 19:24:57 INFO mapred.LocalJobRunner: reduce > copy >
... etc ...
Is there something i have missed?
Thanks for your help in advance!
Best regards,
Björn-Elmar
