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MapReduce, mail # user - Too large class path for map reduce jobs


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Re: Too large class path for map reduce jobs
Tom White 2010-10-07, 20:27
I wonder if there is a misunderstanding here - the problem is that the
classpath has too many classes on it (and clashes with user classes),
rather than it being a text string which is too long.

I would suggest that the technical discussion of how to fix this goes
onto the JIRA.

Cheers,
Tom

On Thu, Oct 7, 2010 at 1:23 AM, Alejandro Abdelnur <[EMAIL PROTECTED]> wrote:
> well, if the issue is a too long classpath, the softlink thingy will give
> some room to breath as the total CP length will be much smaller.
>
> A
> On Thu, Oct 7, 2010 at 3:43 PM, Henning Blohm <[EMAIL PROTECTED]>
> wrote:
>>
>> So that's actually another issue, right? Besides splitting the classpath
>> into those three groups, you want the TT to create soft-links on demand to
>> simplify the computation of classpath string. Is that right?
>>
>> But it's the TT that actually starts the job VM. Why does it matter what
>> the string actually looks like, as long as it has the right content?
>>
>> Thanks,
>>   Henning
>>
>> On Thu, 2010-10-07 at 13:22 +0800, Alejandro Abdelnur wrote:
>>
>> [sent too soon]
>>
>> The first CP shown is how it is today the CP of a task. If we change it
>> pick up all the job JARs from the current dir, then the classpath will be
>> much shorter (second CP shown). We can easily achieve this by soft-linking
>> the job JARs in the work dir of the task.
>>
>> Alejandro
>>
>> On Thu, Oct 7, 2010 at 1:02 PM, Alejandro Abdelnur <[EMAIL PROTECTED]>
>> wrote:
>>
>> Fragmentation of Hadoop classpaths is another issue: hadoop should
>> differentiate the CP in 3:
>>
>> 1*client CP: what is needed to submit a job (only the nachos)
>>
>> 2*server CP (JT/NN/TT/DD): what is need to run the cluster (the whole
>> enchilada)
>>
>> 3*job CP: what is needed to run a job (some of the enchilada)
>>
>>
>> But i'm not trying to get into that here. What I'm suggesting is:
>>
>>
>>
>> -----
>>
>> # Hadoop JARs:
>>
>> /Users/tucu/dev-apps/hadoop/conf
>>
>>
>> /System/Library/Frameworks/JavaVM.framework/Versions/1.6/Home/lib/tools.jar
>>
>> /Users/tucu/dev-apps/hadoop/bin/..
>>
>> /Users/tucu/dev-apps/hadoop/bin/../hadoop-core-0.20.3-CDH3-SNAPSHOT.jar
>>
>> /Users/tucu/dev-apps/hadoop/bin/../lib/aspectjrt-1.6.5.jar
>>
>> ..... (about 30 jars from hadoop lib/ )
>>
>> /Users/tucu/dev-apps/hadoop/bin/../lib/jsp-2.1/jsp-api-2.1.jar
>>
>> # Job JARs (for a job with only 2 JARs):
>>
>>
>> /Users/tucu/dev-apps/hadoop/dirs/mapred/taskTracker/distcache/-2707763075630339038_639898034_1993697040/localhost/user/tucu/oozie-tucu/0000003-101004184132247-oozie-tucu-W/java-node--java/java-launcher.jar
>>
>>
>> /Users/tucu/dev-apps/hadoop/dirs/mapred/taskTracker/distcache/3613772770922728555_-588832047_1993624983/localhost/user/tucu/examples/apps/java-main/lib/oozie-examples-2.2.1-CDH3B3-SNAPSHOT.jar
>>
>>
>> /Users/tucu/dev-apps/hadoop/dirs/mapred/taskTracker/tucu/jobcache/job_201010041326_0058/attempt_201010041326_0058_m_000000_0/work
>>
>> -----
>>
>>
>>
>> What I'm suggesting is that the later group, the job JARs to be
>> soft-linked (by the TT) into the working directory, then their classpath is
>> just:
>>
>> -----
>>
>> java-launcher.jar
>>
>> oozie-examples-2.2.1-CDH3B3-SNAPSHOT.jar
>>
>> .
>>
>> -----
>>
>>
>>
>>
>> Alejandro
>>
>> On Wed, Oct 6, 2010 at 7:57 PM, Henning Blohm <[EMAIL PROTECTED]>
>> wrote:
>>
>> Hi Alejandro,
>>
>>    yes, it can of course be done right (sorry if my wording seemed to
>> imply otherwise). Just saying that I think that Hadoop M/R should not go
>> into that class loader / module separation business. It's one Job, one VM,
>> right? So the problem is to assign just the stuff needed to let the Job do
>> its business without becoming an obstacle.
>>
>>   Must admit I didn't understand your proposal 2. How would that remove
>> (e.g.) jetty libs from the job's classpath?
>>
>> Thanks,
>>   Henning
>>
>> Am Mittwoch, den 06.10.2010, 18:28 +0800 schrieb Alejandro Abdelnur:
>>
>> 1. Classloader business can be done right. Actually it could be done as