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 <[email protected]> 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! :) >>> >>> >>> >> >
