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From Piyush Garg <piyushgar...@gmail.com>
Subject Re: Hadoop basics
Date Sun, 15 Aug 2010 05:04:59 GMT
Hi Rita,

You can put log4j logger debug statements in the code. log4j library is
part of hadoop framework and there is already a log4j.properties file in
hadoop conf directory and all the output logs are saved in hadoop logs
directory.

Thanks and Regards
Piyush Garg


On Sunday 15 August 2010 10:20 AM, Rita Liu wrote:
> Thank you very much, Piyush! :) May I know more about how to use "traces"?
>
> And -- yes, please teach me if possible, experts! :)
>
> Thanks a lot,
> -Rita :))
>
> On Sat, Aug 14, 2010 at 9:42 PM, Piyush Garg <piyushgarg80@gmail.com> wrote:
>
>   
>> Hi Rita,
>>
>> I have just started to learn hadoop as well, I know there is a long way
>> to go.
>> I found some useful links which I am sharing with you.
>>
>> Hadoop Tutorial - YDN
>> <http://developer.yahoo.com/hadoop/tutorial/index.html> excellent
>> beginners tutorial and well organized.
>> Running Hadoop On Ubuntu Linux (Single-Node Cluster) - Michael G. Noll
>> <
>> http://www.michael-noll.com/wiki/Running_Hadoop_On_Ubuntu_Linux_%28Single-Node_Cluster%29
>>     
>>>       
>> Running_Hadoop_On_Ubuntu_Linux_(Multi-Node_Cluster)
>> <
>> http://www.michael-noll.com/wiki/Running_Hadoop_On_Ubuntu_Linux_%28Multi-Node_Cluster%29
>>     
>>>       
>> The tutorial on the hadoop wiki
>> <http://hadoop.apache.org/common/docs/r0.20.0/mapred_tutorial.html> is
>> too much for a beginner.
>>
>> Debugger:
>> I do not think you can easily do debugging using remote debugger. This
>> is natural since hadoop is not sequential programming, it would be very
>> difficult to debug its apps.
>> The only way to debug is to use traces.
>>
>> I think you can learn how to setup multi-node cluster, but for practice
>> session you can use single node setup.
>>
>> Lets see what the experts say.
>>
>> Thanks and Regards
>> Piyush Garg
>>
>>
>> On Sunday 15 August 2010 09:07 AM, Rita Liu wrote:
>>     
>>> Hi!
>>>
>>> I am a total beginner, but I am very interested in hadoop. I've already
>>> downloaded hadoop 0.19.2 and run on Ubuntu in single-node mode. Now I
>>>       
>> want
>>     
>>> to do two things:
>>>
>>> 1. Explore how hadoop works internally with one of the example
>>>       
>> applications
>>     
>>> hadoop provides
>>> 2. Write an application on my own
>>>
>>> Those two things bring me following questions:
>>>
>>> a. debugger?
>>> I am stuck since I don't know how to "explore" hadoop. I used to trace
>>> through the code using a debugger, but in this case, I don't know if
>>>       
>> there
>>     
>>> is a good debugger to use; or -- maybe a debugger is not necessary for
>>> hadoop? If not, then how do you trace through the code to either debug or
>>> just gain an understanding about the system? May I know what you,
>>> experienced experts, do? :)
>>>
>>> b. Where to run hadoop?
>>> Also -- may I know where you run your hadoop? Do you run on linux, or on
>>>       
>> VM
>>     
>>> -- in particular, Cloudera? I heard that Cloudera is good for writing
>>> mapreduce applications with hadoop itself as a blackbox; is it true? If
>>>       
>> my
>>     
>>> ultimate goal is to understand how hadoop works internally, would it be
>>> better if I directly run it on linux?
>>>
>>> c. Single-node or multi-node?
>>> In the beginning (just like my case :p) would it be better to use
>>> single-node or multi-node? If the latter is true, should I obtain more
>>> machines, or should I use more virtual machines to create more nodes?
>>>
>>> As a newbie, I am sorry for all those basic (and silly, I know :$)
>>> questions. If possible, please help me out? Any suggestion or advice will
>>>       
>> be
>>     
>>> greatly appreciated. Thank you very much!
>>>
>>> Best,
>>> Rita :)
>>>
>>> P.S. If my questions are not suitable for this mailing-list, please let
>>>       
>> me
>>     
>>> apologize, and then, could you please direct me to other mailing-lists?
>>> Sorry, and thanks a lot! :)
>>>
>>>
>>>       
>>     
>   

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