MMapDirectory on Windows silently fails to write to a file if also open for read
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Key: LUCENE-1669
URL: https://issues.apache.org/jira/browse/LUCENE-1669
Project: Lucene - Java
Issue Type: Bug
Components: Store
Reporter: Michael McCandless
Priority: Minor
This is not a normal situation Lucene currently encounters, though we
are discussing exactly this possibility in LUCENE-1313.
I only hit it in digging down on a test failure in LUCENE-1658:
{code}
[junit] Testcase: testIndexAndMerge(org.apache.lucene.index.TestDoc):
FAILED
[junit] junit.framework.AssertionFailedError:
[junit] at
org.apache.lucene.index.FieldsWriter.addRawDocuments(FieldsWriter.java:249)
[junit] at
org.apache.lucene.index.SegmentMerger.mergeFields(SegmentMerger.java:350)
[junit] at
org.apache.lucene.index.SegmentMerger.merge(SegmentMerger.java:139)
[junit] at
org.apache.lucene.index.SegmentMerger.merge(SegmentMerger.java:116)
[junit] at org.apache.lucene.index.TestDoc.merge(TestDoc.java:182)
[junit] at
org.apache.lucene.index.TestDoc.testIndexAndMerge(TestDoc.java:117)
[junit] at
org.apache.lucene.util.LuceneTestCase.runTest(LuceneTestCase.java:88)
{code}
That failure happens on Windows 64bit, if you use MMapDirectory, and
the index is on a remote (CIFS) mount.
This test opens a SegmentReader against doc store files that
IndexWriter still has open.
I whittled it down to this test showing the root cause:
{code}
public void testMMapWriteRead() throws Exception {
MMapDirectory dir = new MMapDirectory(new File("readwrite"), null);
//NIOFSDirectory dir = new NIOFSDirectory(new File("readwrite"), null);
//SimpleFSDirectory dir = new SimpleFSDirectory(new File("readwrite"),
null);
IndexOutput out = dir.createOutput("one");
out.writeLong(17);
out.flush();
// open the same file we are writing
dir.openInput("one").close();
// write another long
out.writeLong(56);
out.close();
IndexInput in = dir.openInput("one");
assertEquals(17, in.readLong());
assertEquals(56, in.readLong());
in.close();
}
{code}
NIOFSDir and SimpleFSDir pass the test fine, which is nice to know
(for LUCENE-1313). MMapDir passes fine on a local drive, but fails on
a remote CIFS mount.
I'm not sure what's going on. It seems like it could be a JRE bug --
behavior shouldn't change on local vs remote drive. I've only tested
it with java 1.6.0_11.
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