[
https://issues.apache.org/jira/browse/MAPREDUCE-1901?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12897833#action_12897833
]
Koji Noguchi commented on MAPREDUCE-1901:
-----------------------------------------
bq. we have started testing this patch internally and this would become
production in a couple of weeks.
Joydeep, is this being tested on your production? How does the load look like?
I don't know the details, but I like the "part of the goal here is to not have
to look up mtimes again and again. " part.
We certainly have applications with many small tasks having multiple
libjar/distributed-caches resulting with too many getfileinfo calls to the
namenode.
> Jobs should not submit the same jar files over and over again
> -------------------------------------------------------------
>
> Key: MAPREDUCE-1901
> URL: https://issues.apache.org/jira/browse/MAPREDUCE-1901
> Project: Hadoop Map/Reduce
> Issue Type: Improvement
> Reporter: Joydeep Sen Sarma
> Attachments: 1901.PATCH
>
>
> Currently each Hadoop job uploads the required resources
> (jars/files/archives) to a new location in HDFS. Map-reduce nodes involved in
> executing this job would then download these resources into local disk.
> In an environment where most of the users are using a standard set of jars
> and files (because they are using a framework like Hive/Pig) - the same jars
> keep getting uploaded and downloaded repeatedly. The overhead of this
> protocol (primarily in terms of end-user latency) is significant when:
> - the jobs are small (and conversantly - large in number)
> - Namenode is under load (meaning hdfs latencies are high and made worse, in
> part, by this protocol)
> Hadoop should provide a way for jobs in a cooperative environment to not
> submit the same files over and again. Identifying and caching execution
> resources by a content signature (md5/sha) would be a good alternative to
> have available.
--
This message is automatically generated by JIRA.
-
You can reply to this email to add a comment to the issue online.
