[LUCENE-4462] Publishing flushed segments is single threaded and too costly

• Type: Improvement
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 4.0-ALPHA, 4.0-BETA, 4.0
• Fix Version/s: 4.1, 6.0
• Component/s: core/index
• Lucene Fields: New, Patch Available
• Assignee: Simon Willnauer
• Reporter: Michael McCandless
• Created: 05/Oct/12 18:47
• Updated: 28/Aug/22 13:29
• Resolved: 11/Oct/12 19:13

Description

Spinoff from http://lucene.markmail.org/thread/4li6bbomru35qn7w

The new TestBagOfPostings failed the build because it timed out after 2 hours ... but in digging I found that it was a starvation issue: the 4 threads were flushing segments much faster than the 1 thread could publish them.

I think this is because publishing segments (DocumentsWriter.publishFlushedSegment) is actually rather costly (creates CFS file if necessary, writes .si, etc.).

I committed a workaround for now, to prevent starvation (see svn diff -c 1394704 https://svn.apache.org/repos/asf/lucene/dev/trunk), but we really should address the root cause by moving these costly ops into flush() so that publishing is a low cost operation.