On Wed, Jun 13, 2012 at 8:45 PM, Itamar Syn-Hershko <ita...@code972.com> wrote: > Mike, > > On Wed, Jun 13, 2012 at 7:31 PM, 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. > > > Definitely, as Christopher noted we are about to release a 3.0.3 compatible > version, which is line-by-line port of the Java version.
Hmm OK. Then we still need to explain the corruption... >> 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). > > Somewhat unrelated to this thread, but what should I expect to see? from > time to time we do see write.lock present after an app-crash or power > failure. Also, what are the steps that are expected to be performed in such > cases? If you are using NativeFSLockFactory, you will see a write.lock but it will not actually be locked (according to the OS); so, it's fine. If you are using SimpleFSLockFactory then the presence of write.lock means the index is still locked and you'll have to remove it. >> > 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... > > Ok, so we do have fsync since LUCENE-1044 is present, and there were > segments present from previous commits. Any idea what went wrong? I don't know! >> > 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...). > > So 2328 broke 1044, and this was fixed only in 3.4, right? so 2328 made it > to a 3.0.x release while the fix for it (3418) was only released in 3.4. Am > I right? > > If this is the case, 2328 probably made it's way to Lucene.Net since we are > using the released sources for porting, and we now need to apply 3418 in the > current version. OK that makes sense: 2328 broke things as of 3.0.3, and 3418 fixed things in 3.4. > Does it make sense to just port FSDirectory from 3.4 to 3.0.3? or were there > API or other changes that will make our life miserable if we do that? Hmmm I'm not certain offhand: maybe diff the two sources? The fix in 3418 was trivial in the end, so maybe just backport that. >> > 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 suspected. Will try to reproduce reliably - any recommendations? not > really feeling like reinventing the wheel here... > > MockDirectoryWrapper wasn't ported yet as it appears to only appear in 3.4, > and as you said it won't really help here anyway Use a spare computer and try pulling the plug on it ... or pull a (hot swappable/pluggable) hard drive while indexing onto it ... You can also use a virtual machine and power it off ungracefully / kill the process. If any of these events can corrupt the index then there's a bug somewhere (or: the IO system ignores fsync). 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
