Christopher, I used the IndexBuilder app from here https://github.com/synhershko/Talks/tree/master/LuceneNeatThings with a 8.5GB wikipedia dump.
After running for 2.5 days I had to forcefully close it (infinite loop in the wiki-markdown parser at 92%, go figure), and the 40-something GB index I had by then was unusable. I then was able to reproduce this Please note I now added a few safe-guards you might want to remove to make sure the app really crashes on process kill. I'll try to come up with a better way to reproduce this - hopefully Mike will be able to suggest better ways than manual process kill... On Thu, Jun 14, 2012 at 1:41 AM, Christopher Currens < currens.ch...@gmail.com> wrote: > 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 > > >
