Right: Lucene never autocommits anymore ... If you create a new index, add a bunch of docs, and things crash before you have a chance to commit, then there is no index (not even a 0 doc one) in that directory.
Mike McCandless http://blog.mikemccandless.com On Thu, Jun 14, 2012 at 1:41 PM, Itamar Syn-Hershko <ita...@code972.com> wrote: > I'm quite certain this shouldn't happen also when Commit wasn't called. > > Mike, can you comment on that? > > On Thu, Jun 14, 2012 at 8:03 PM, Christopher Currens > <currens.ch...@gmail.com> wrote: >> >> Well, the only thing I see is that there is no place where writer.Commit() >> is called in the delegate assigned to corpusReader.OnDocument. I know >> that >> lucene is very transactional, and at least in 3.x, the writer will never >> auto commit to the index. You can write millions of documents, but if >> commit is never called, those documents aren't actually part of the index. >> Committing isn't a cheap operation, so you definitely don't want to do it >> on every document. >> >> You can test it yourself with this (naive) solution. Right below the >> writer.SetUseCompoundFile(false) line, add "int numDocsAdded = 0;". At >> the >> end of the corpusReader.OnDocument delegate add: >> >> // Example only. I wouldn't suggest committing this often >> if(++numDocsAdded % 5 == 0) >> { >> writer.Commit(); >> } >> >> I had the application crash for real on this file: >> >> http://dumps.wikimedia.org/gawiktionary/20120613/gawiktionary-20120613-pages-meta-history.xml.bz2, >> about 20% into the operation. Without the commit, the index is empty. >> Add >> it in, and I get 755 files in the index after it crashes. >> >> >> Thanks, >> Christopher >> >> On Wed, Jun 13, 2012 at 6:13 PM, Itamar Syn-Hershko >> <ita...@code972.com>wrote: >> >> >> > Yes, reproduced in first try. See attached program - I referenced it to >> > current trunk. >> > >> > >> > On Thu, Jun 14, 2012 at 3:54 AM, Itamar Syn-Hershko >> > <ita...@code972.com>wrote: >> > >> >> 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 >> >>> > >> >>> >> >> >> >> >> > > > --------------------------------------------------------------------- To unsubscribe, e-mail: dev-unsubscr...@lucene.apache.org For additional commands, e-mail: dev-h...@lucene.apache.org
