[OOZIE-3232] Reduce heap waste by reducing duplicate string count

• Type: Improvement
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 5.1.0
• Component/s: core
• Assignee: Misha Dmitriev
• Reporter: Misha Dmitriev
• Created: 04/May/18 02:17
• Updated: 18/Jan/19 09:02
• Resolved: 08/May/18 15:20

Description

I've recently analyzed an Oozie heap dump obtained from a customer's production job, using jxray (www.jxray.com). In this job, Oozie's heap consumption is ~6GB, and it turns out that nearly 25% of it is wasted due to a large number of duplicate strings. The screenshot below, taken from the jxray report, illustrates the problem.

It turns out that a lot of duplicate strings come from the oozie's own code, i.e. org.apache.oozie.*. In particular, the top data field wasting memory is org.apache.oozie.StringBlob.string (wastes 2.6%, or ~160MB). From the source code of StringBlob I see that it would be trivial to intern (deduplicate) these strings by adding the call to String.intern() in the constructor and a few other places. Similarly, various fields of org.apache.oozie.WorkflowJobBean and WorkflowActionBean collectively waste a lot of memory, and can be fixed in the same way.

Issue Links

• is related to: OOZIE-3250 Reduce heap waste by reducing duplicate byte[] count