Michael McCandless created LUCENE-4462:
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             Summary: Publishing flushed segments is single threaded and too 
costly
                 Key: LUCENE-4462
                 URL: https://issues.apache.org/jira/browse/LUCENE-4462
             Project: Lucene - Core
          Issue Type: Improvement
            Reporter: Michael McCandless


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.

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