[LUCENE-823] Lucene fails to close file handles under certain situations

• Type: Bug
• Status: Closed
• Priority: Minor
• Resolution: Fixed
• Affects Version/s: 2.1
• Fix Version/s: 2.2
• Component/s: core/index
• Lucene Fields: New, Patch Available
• Assignee: Michael McCandless
• Reporter: Michael McCandless
• Created: 04/Mar/07 09:15
• Updated: 28/Aug/22 11:35
• Resolved: 06/Mar/07 21:45

Description

As a followon to LUCENE-820, I've added a further check in
MockRAMDirectory to assert that there are no open files when the
directory is closed.

That check caused a few unit tests to fail, and in digging into the
reason I uncovered these cases where Lucene fails to close file
handles:

• TermInfosReader.close() was setting its ThreadLocal enumerators to
  null without first closing the SegmentTermEnum in there. It looks
  like this was part of the fix for LUCENE-436. I just added the
  call to close.

This is somewhat severe since we could leak many file handles for
use cases that burn through threads and/or indexes. Though,
FSIndexInput does have a finalize() to close itself.

• Flushing of deletes in IndexWriter opens SegmentReader to do the
  flushing, and it correctly calls close() to close the reader. But
  if an exception is hit during commit and before actually closing,
  it will leave open those handles. I fixed this first calling
  doCommit() and then doClose() in a finally. The "disk full" tests
  we now have were hitting this.

• IndexWriter's addIndexes(IndexReader[]) method was opening a
  reader but not closing it with a try/finally. I just put a
  try/finally in.

I've also changed some unit tests to use MockRAMDirectory instead of
RAMDirectory to increase testing coverage of "leaking open file
handles".