[SOLR-7319] Workaround the "Four Month Bug" causing GC pause problems

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Information Provided
• Affects Version/s: 5.0
• Component/s: scripts and tools
• Assignee: Shawn Heisey
• Reporter: Shawn Heisey
• Created: 27/Mar/15 14:23
• Updated: 03/Oct/16 15:44
• Resolved: 03/Oct/16 15:44

Description

A twitter engineer found a bug in the JVM that contributes to GC pause problems:

http://www.evanjones.ca/jvm-mmap-pause.html

Problem summary (in case the blog post disappears): The JVM calculates statistics on things like garbage collection and writes them to a file in the temp directory using MMAP. If there is a lot of other MMAP write activity, which is precisely how Lucene accomplishes indexing and merging, it can result in a GC pause because the mmap write to the temp file is delayed.

We should implement the workaround in the solr start scripts (disable creation of the mmap statistics tempfile) and document the impact in CHANGES.txt.