[MAPREDUCE-1901] Jobs should not submit the same jar files over and over again

• Type: Improvement
• Status: Resolved
• Priority: Major
• Resolution: Duplicate
• Assignee: Unassigned
• Reporter: Joydeep Sen Sarma
• Created: 30/Jun/10 19:21
• Updated: 13/Nov/15 18:57
• Resolved: 13/Nov/15 18:57

Description

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.

Issue Links

• is duplicated by: YARN-1492 truly shared cache for jars (jobjar/libjar)
• relates to: MAPREDUCE-1902 job jar file is not distributed via DistributedCache