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From "Robert Joseph Evans (Commented) (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (MAPREDUCE-3323) Add new interface for Distributed Cache, which special for Map or Reduce,but not Both.
Date Mon, 07 Nov 2011 18:20:52 GMT

    [ https://issues.apache.org/jira/browse/MAPREDUCE-3323?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13145669#comment-13145669

Robert Joseph Evans commented on MAPREDUCE-3323:

I have read through all of your patches and I have a few comments.

# I don't really like the name of current.task.type.internal.  It would be better to prefix
it with mapreduce.  
# I think it is slightly faster to change {code}fileURI.toArray(new URI[0]){code} to {code}fileURI.toArray(new
URI[fileURI.size()]){code}, but this is just a nit.
# There are no tests in the patches.  I know you have done some manual testing, but adding/updating
the unit tests is important for this to be accepted in.
# Have you tested add(Archive|File)ToClassPathFor(Map|Reduce)?  They set "mapred.job.classpath.(archives|files)"
so if you use these methods some of the entries in "mapred.job.classpath.(archives|files)"
will not be valid
# Why are you setting CACHE_(FILE|ARCHIVE)_FOR_(MAP|REDUCE)?  It seems like you could just
go off of the existence of CACHE_(ARCHIVES|FILES)_(MAP|REDUCE).
# could you please add in the new user facing configuration keys to mapred-default.xml so
that they are documented.

> Add new interface for Distributed Cache, which special  for Map or Reduce,but not Both.
> ---------------------------------------------------------------------------------------
>                 Key: MAPREDUCE-3323
>                 URL: https://issues.apache.org/jira/browse/MAPREDUCE-3323
>             Project: Hadoop Map/Reduce
>          Issue Type: Improvement
>          Components: distributed-cache, tasktracker
>    Affects Versions:
>            Reporter: Azuryy(Chijiong)
>             Fix For:
>         Attachments: DistributedCache.patch, GenericOptionsParser.patch, JobClient.patch,
TaskDistributedCacheManager.patch, TaskTracker.patch
> We put some file into Distributed Cache, but sometimes, only Map or Reduce use thses
cached files, not useful for both. but TaskTracker always download cached files from HDFS,
if there are some little bit big files in cache, it's time expensive.
> so, this patch add some new API in the DistributedCache.java as follow:
> addArchiveToClassPathForMap
> addArchiveToClassPathForReduce
> addFileToClassPathForMap
> addFileToClassPathForReduce
> addCacheFileForMap
> addCacheFileForReduce
> addCacheArchiveForMap
> addCacheArchiveForReduce
> New API doesn't affect original interface. User can use these features like the following
two methods:
> 1) 
> hadoop job **** -files file1 -mapfiles file2 -reducefiles file3 -archives arc1 -maparchives
arc2 -reduce archives arc3
> 2)
> DistributedCache.addCacheFile(conf, file1);
> DistributedCache.addCacheFileForMap(conf, file2);
> DistributedCache.addCacheFileForReduce(conf, file3);
> DistributedCache.addCacheArchives(conf, arc1);
> DistributedCache.addCacheArchivesForMap(conf, arc2);
> DistributedCache.addCacheFArchivesForReduce(conf, arc3);
> These two methods have the same result, That's mean: 
> You put six files to the distributed cache: file1 ~ file3, arc1 ~ arc3, 
> but file1 and arc1 are cached for both map and reduce;
> file2 and arc2 are only cached for map;
> file3 and arc3 are only cached for reduce;

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