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MapReduce >> mail # user >> Why is Hadoop always running just 4 tasks?


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Re: Why is Hadoop always running just 4 tasks?
I am not sure if Hadoop detects that. I guess that it will run one map
tasks for them. Please let me know, if I am wrong.
2013/12/11 Dror, Ittay <[EMAIL PROTECTED]>

> OK, thank you for the solution.
>
> BTW I just concatenated several .gz files together with cat  (without
> uncompressing first). So they should each uncompress individually
>
>
>
> From: Adam Kawa <[EMAIL PROTECTED]>
> Reply-To: "[EMAIL PROTECTED]" <[EMAIL PROTECTED]>
> Date: Wednesday, December 11, 2013 9:33 PM
>
> To: "[EMAIL PROTECTED]" <[EMAIL PROTECTED]>
> Subject: Re: Why is Hadoop always running just 4 tasks?
>
> mapred.map.tasks is rather a hint to InputFormat (
> http://wiki.apache.org/hadoop/HowManyMapsAndReduces) and it is ignored in
> your case.
>
> You process gz files, and InputFormat has isSplitatble method that for gz
> files it returns false, so that each map tasks process a whole file (this
> is related with gz files - you can not uncompress a part of gzipped file.
> To uncompress it, you must read it from the beginning to the end).
>
>
>
>
> 2013/12/11 Dror, Ittay <[EMAIL PROTECTED]>
>
>> Thank you.
>>
>> The command is:
>> hadoop jar /tmp/Algo-0.0.1.jar com.twitter.scalding.Tool com.akamai.Algo
>> --hdfs --header --input /algo/input{0..3}.gz --output /algo/output
>>
>> Btw, the Hadoop version is 1.2.1
>>
>> Not sure what driver you are referring to.
>> Regards,
>> Ittay
>>
>> From: Mirko Kämpf <[EMAIL PROTECTED]>
>> Reply-To: "[EMAIL PROTECTED]" <[EMAIL PROTECTED]>
>> Date: Wednesday, December 11, 2013 6:21 PM
>> To: "[EMAIL PROTECTED]" <[EMAIL PROTECTED]>
>> Subject: Re: Why is Hadoop always running just 4 tasks?
>>
>> Hi,
>>
>> what is the command you execute to submit the job?
>> Please share also the driver code ....
>>
>> So we can troubleshoot better.
>>
>> Best wishes
>> Mirko
>>
>>
>>
>>
>> 2013/12/11 Dror, Ittay <[EMAIL PROTECTED]>
>>
>>> I have a cluster of 4 machines with 24 cores and 7 disks each.
>>>
>>> On each node I copied from local a file of 500G. So I have 4 files in
>>> hdfs with many blocks. My replication factor is 1.
>>>
>>> I run a job (a scalding flow) and while there are 96 reducers pending,
>>> there are only 4 active map tasks.
>>>
>>> What am I doing wrong? Below is the configuration
>>>
>>> Thanks,
>>> Ittay
>>>
>>> <configuration>
>>> <property>
>>> <name>mapred.job.tracker</name>
>>>  <value>master:54311</value>
>>> </property>
>>>
>>> <property>
>>>  <name>mapred.map.tasks</name>
>>>  <value>96</value>
>>> </property>
>>>
>>> <property>
>>>  <name>mapred.reduce.tasks</name>
>>>  <value>96</value>
>>> </property>
>>>
>>> <property>
>>> <name>mapred.local.dir</name>
>>>
>>> <value>/hdfs/0/mapred/local,/hdfs/1/mapred/local,/hdfs/2/mapred/local,/hdfs/3/mapred/local,/hdfs/4/mapred/local,/hdfs/5/mapred/local,/hdfs/6/mapred/local,/hdfs/7/mapred/local</value>
>>> </property>
>>>
>>> <property>
>>> <name>mapred.tasktracker.map.tasks.maximum</name>
>>> <value>24</value>
>>> </property>
>>>
>>> <property>
>>>     <name>mapred.tasktracker.reduce.tasks.maximum</name>
>>>     <value>24</value>
>>> </property>
>>> </configuration>
>>>
>>
>>
>