[HADOOP-3280] virtual address space limits break streaming apps

• Type: Bug
• Status: Closed
• Priority: Blocker
• Resolution: Fixed
• Fix Version/s: 0.17.0
• Hadoop Flags: Incompatible change, Reviewed
• Release Note: This patch adds the mapred.child.ulimit to limit the virtual memory for children processes to the given value.
• Assignee: Arun Murthy
• Reporter: Rick Cox
• Created: 18/Apr/08 17:07
• Updated: 08/Jul/09 17:05
• Resolved: 29/Apr/08 22:46

Description

HADOOP-2765 added a mandatory, hard virtual address space limit to streaming apps based on the Java process's -Xmx setting.

This makes it impossible to run a 64-bit streaming app that needs large address spaces under a 32-bit JVM, even if one is otherwise willing to dramatically increase the -Xmx setting without cause. Also, unlike Java's -Xmx limit, the virtual address space limit for an arbitrary UNIX process does not necessarily correspond to RAM usage, so it's likely to be a relatively difficult to configure limit.

2765 was originally opened to allow an optional wrapper script around streaming tasks, one use case for which was setting a ulimit. That approach seems much less intrusive and more flexible than the final implementation. The ulimit can also be trivially set by the streaming task itself without any support from Hadoop.

Marking this as an 0.17 blocker because it will break deployed apps and there is no workaround available.