Mike, The codebase for lucene.net should be almost identical to java's 3.0.3 release, and LUCENE-1044 is included in that.
Itamar, are you committing the index regularly? I only ask because I can't reproduce it myself by forcibly terminating the process while it's indexing. I've tried both 3.0.3 and 2.9.4. If I don't commit at all and terminate the process (even with a 10,000 4K documents created), there will be no documents in the index when I open it in luke, which I expect. If I commit at 10,000 documents, and terminate it a few thousand after that, the index has the first ten thousand that were committed. I've even terminated it *while* a second commit was taking place, and it still had all of the documents I expected. It may be that I'm not trying to reproducing it correctly. Do you have a minimal amount of code that can reproduce it? Thanks, Christopher On Wed, Jun 13, 2012 at 9:31 AM, Michael McCandless < luc...@mikemccandless.com> wrote: > Hi Itamar, > > One quick question: does Lucene.Net include the fixes done for > LUCENE-1044 (to fsync files on commit)? Those are very important for > an index to be intact after OS/JVM crash or power loss. > > More responses below: > > On Tue, Jun 12, 2012 at 8:20 PM, Itamar Syn-Hershko <ita...@code972.com> > wrote: > > > I'm a Lucene.Net committer, and there is a chance we have a bug in our > > FSDirectory implementation that causes indexes to get corrupted when > > indexing is cut while the IW is still open. As it roots from some > > retroactive fixes you made, I'd appreciate your feedback. > > > > Correct me if I'm wrong, but by design Lucene should be able to recover > > rather quickly from power failures or app crashes. Since existing segment > > files are read only, only new segments that are still being written can > get > > corrupted. Hence, recovering from worst-case scenarios is done by simply > > removing the write.lock file. The worst that could happen then is having > the > > last segment damaged, and that can be fixed by removing those files, > > possibly by running CheckIndex on the index. > > You shouldn't even have to run CheckIndex ... because (as of > LUCENE-1044) we now fsync all segment files before writing the new > segments_N file, and then removing old segments_N files (and any > segments that are no longer referenced). > > You do have to remove the write.lock if you aren't using > NativeFSLockFactory (but this has been the default lock impl for a > while now). > > > Last week I have been playing with rather large indexes and crashed my > app > > while it was indexing. I wasn't able to open the index, and Luke was even > > kind enough to wipe the index folder clean even though I opened it in > > read-only mode. I re-ran this, and after another crash running CheckIndex > > revealed nothing - the index was detected to be an empty one. I am not > > entirely sure what could be the cause for this, but I suspect it has > > been corrupted by the crash. > > Had no commit completed (no segments file written)? > > If you don't fsync then all sorts of crazy things are possible... > > > I've been looking at these: > > > > > https://issues.apache.org/jira/browse/LUCENE-3418?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel > > > https://issues.apache.org/jira/browse/LUCENE-2328?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel > > (And LUCENE-1044 before that ... it was LUCENE-1044 that LUCENE-2328 > broke...). > > > And it seems like this is what I was experiencing. Mike and Mark will > > probably be able to tell if this is what they saw or not, but as far as I > > can tell this is not an expected behavior of a Lucene index. > > Definitely not expected behavior: assuming nothing is flipping bits, > then on OS/JVM crash or power loss your index should be fine, just > reverted to the last successful commit. > > > What I'm looking for at the moment is some advice on what FSDirectory > > implementation to use to make sure no corruption can happen. The 3.4 > version > > (which is where LUCENE-3418 was committed to) seems to handle a lot of > > things the 3.0 doesn't, but on the other hand LUCENE-3418 was introduced > by > > changes made to the 3.0 codebase. > > Hopefully it's just that you are missing fsync! > > > Also, is there any test in the suite checking for those scenarios? > > Our test framework has a sneaky MockDirectoryWrapper that, after a > test finishes, goes and corrupts any unsync'd files and then verifies > the index is still OK... it's good because it'll catch any times we > are missing calls t sync, but, it's not low level enough such that if > FSDir is failing to actually call fsync (that wsa the bug in > LUCENE-3418) then it won't catch that... > > Mike McCandless > > http://blog.mikemccandless.com >
