Resolution: Won't Fix
Affects Version/s: 2.0.0
Fix Version/s: None
When interleaving adds and removes there is frequent opening/closing of readers and writers.
I tried to measure performance in such a scenario (for issue 565), but the performance test failed - the indexing process crashed consistently with file "access denied" errors - "cannot create a lock file" in "lockFile.createNewFile()" and "cannot rename file".
This is related to:
- issue 516 (a closed issue: "TestFSDirectory fails on Windows") - http://issues.apache.org/jira/browse/LUCENE-516
- user list questions due to file errors:
- discussion on lock-less commits http://www.nabble.com/Lock-less-commits-tf2126935.html
My test setup is: XP (SP1), JAVA 1.5 - both SUN and IBM SDKs.
I noticed that the problem is more frequent when locks are created on one disk and the index on another. Both are NTFS with Windows indexing service enabled. I suspect this indexing service might be related - keeping files busy for a while, but don't know for sure.
After experimenting with it I conclude that these problems - at least in my scenario - are due to a temporary situation - the FS, or the OS, is temporarily holding references to files or folders, preventing from renaming them, deleting them, or creating new files in certain directories.
So I added to FSDirectory a retry logic in cases the error was related to "Access Denied". This is the same approach brought in http://www.nabble.com/running-a-lucene-indexing-app-as-a-windows-service-on-xp%2C-crashing-tf2053536.html - there, in addition to the retry, gc() is invoked (I did not gc()). This is based on the hope that a access-denied situation would vanish after a small delay, and the retry would succeed.
I modified FSDirectory this way for "Access Denied" errors during creating a new files, renaming a file.
This worked fine for me. The performance test that failed before, now managed to complete. There should be no performance implications due to this modification, because only the cases that would otherwise wrongly fail are now delaying some extra millis and retry.
I am attaching here a patch - FSDirectory_Retry_Logic.patch - that has these changes to FSDirectory.
All "ant test" tests pass with this patch.
Also attaching a test case that demostrates the problem - at least on my machine. There two tests cases in that test file - one that works in system temp (like most Lucene tests) and one that creates the index in a different disk. The latter case can only run if the path ("D:" , "tmp") is valid.
It would be great if people that experienced these problems could try out this patch and comment whether it made any difference for them.
If it turns out useful for others as well, including this patch in the code might help to relieve some of those "frustration" user cases.
A comment on state of proposed patch:
- It is not a "ready to deploy" code - it has some debug printing, showing the cases that the "retry logic" actually took place.
- I am not sure if current 30ms is the right delay... why not 50ms? 10ms? This is currently defined by a constant.
- Should a call to gc() be added? (I think not.)
- Should the retry be attempted also on "non access-denied" exceptions? (I think not).
- I feel it is somewhat "woodoo programming", but though I don't like it, it seems to work...
1. TestInterleavedAddAndRemoves.java - the LONG test that fails on XP without the patch and passes with the patch.
3. Test_Output.txt- output of the test with the patch, on my XP. Only the createNewFile() case had to be bypassed in this test, but for another program I also saw the renameFile() being bypassed.