Database corruption is not esoteric, we take it very seriously. :) Yes, strictly append only (opened with O_APPEND in posix land, not sure what the equivalent is for Win). This doesn’t stop hardware failure from mangling earlier bits, of course. You have RAID-5, so you have a parity stripe, perhaps you could force a parity check? Abrupt shutdown or hitting end of disk should do no more than cause unflushed updates to be lost, nothing fsync’ed() prior to that should be at risk, by design. Are you running with delayed_commits equal true or false? The difference is that we fsync immediately or at up to a one second delay. In neither case do we omit to make fsync() calls before and after writing each new database footer. There are config options to disable those fsync calls, please let us know if you did that (your local.ini file will tell you).
So, the two causes of true corruption would be 1) a bug in our code and 2) disk corruption or failure to honor fsync() and/or write ordering. Obviously we’re very interested in any occurrence of type 1. A few things to try to confirm that your database is ok but not compactable (which would be hard to explain) curl localhost:5984/dbname/_changes?include_docs=true curl localhost:5984/dbname/_all_docs?include_docs=true Let us know if those complete without error (or the errors if there are any). Finally, would it be possible for the CouchDB development team (or a subset) to receive a copy of the database file for forensic investigation? I believe we can sign NDA’s and the like if that helps. B. On 23 Jan 2014, at 13:54, Igor Klimer <[email protected]> wrote: > No problem - I'm sure that you have more then enough on your plate without > users pestering you with such esoteric problems ;) > > As for the I/O subsystem - on the lowest level it's a couple of RAID5 > matrices. Then, there is a Windows Server 2008 managing that and some virtual > servers (via Hyper-V), including both of the machines that we had the > database on (Windows Server 2008 R2 Enterprise and now Ubuntu 12 LTS). I was > assured that the matrices have been running rock-solid since the moment > they've been setup and didn't exhibit any hardware failures. However, the > servers could have been abruptly shut down, for example when it run out of > free disk space. While NTFS should recover from something like that, I wonder > if there isn't a corner case that would cause some database corruption (like > you're suggesting). > > Thanks for the recover-couchdb script - I'll try to give it a go ASAP. We do > have backups, but I don't think they are helpful in this case - the database > as a whole is working, we don't have any reports of missing files or not > working documents. It would be interesting to inspect the backups to see when > and, more interestingly, what happened. You mentioned that the database > format is strictly append only, so the corruption shouldn't "move" and the > "old"/early parts of the database file shouldn't change? Still, that seems > like a really time consuming task, so for now I'll try to give the recovery > script a go. > > Thanks again for your help and best regards, > Igor Klimer > > ________________________________________ > Od: Robert Samuel Newson [[email protected]] > Wysłano: 23 stycznia 2014 13:52 > Do: user > Temat: Re: Error during compaction > > Hi, > > Sorry, in turn, for not replying sooner. I’m not really sure what to suggest, > it does sound like the database file is corrupt, which is quite hard to do > with our strictly append only format. The only oddities here are the use of > Windows (and, presumably, NTFS?) and the fact that you did hit end of disk. > I’ve not observed corruption when hitting end of disk on other OS/FS > combinations, though. Do you happen to know any details of your I/O subsystem > that might provide a hint? Could any of the disks themselves have suffered > block failures that couldn’t be corrected by disk firmware? Bit flips?Would > your disk controller lie about fsync() calls? > > Those questions will help us figure out how the corruption occurs, but it > obviously doesn’t help you fix it. For that, beyond hoping you have backups, > I suggest trying https://github.com/jhs/recover-couchdb (perhaps Jason can > chip in with how likely this is to still work, given the age). If that > doesn’t extract all your data, then the only other suggestion I have is to > truncate the database file until it can compact, but this necessarily means > losing data. > > Do other developers have other suggestions here? > > B. > > On 21 Jan 2014, at 09:08, Igor Klimer <[email protected]> wrote: > >> Hi, >> I'm extremely sorry for not replying sooner, however I was on sick leave >> last week. >> I've tried your suggestion with an empty .compact file, however the results >> seem to be the same... >> Log: http://pastebin.com/MJCgGM8C >> >> Started with an empty ecrepo.couch.compact file (touch >> ecrepo.couch.compact), then after about 3 hours, the error was printed in >> the logs and the compaction failed: >> -rw-r--r-- 1 couchdb couchdb 137502523517 Jan 21 09:51 ecrepo.couch >> -rw-r--r-- 1 couchdb couchdb 51692612367 Jan 21 02:07 ecrepo.couch.compact >> >> There's over 100GB free space available on the disk. >> >> At least I think I know what the number 51692471440 in log means ;) But I >> don't know if there's a way to check which document resides at that position >> in file. >> >> Best regards, >> Igor Klimer >> >> ________________________________________ >> Od: Robert Samuel Newson [[email protected]] >> Wysłano: 10 stycznia 2014 18:45 >> Do: user >> Temat: Re: Error during compaction >> >> Yes, I understood. The empty .compact file will trigger more checking in the >> compaction process, I’m hoping it gets us past the problem. >> >> B. >> >> On 10 Jan 2014, at 13:34, Igor Klimer <[email protected]> wrote: >> >>> :) >>> Just to clarify - the .compact file is getting created and then the >>> compaction fails after some time (an hour or more): >>> 1) attempt on Windows with Couchdb 1.2.0 it failed because insufficient >>> disk space. The .compact file had at least 10GB, unfortunately, I don't >>> remember how much (and whether it was bigger then the one produced in the >>> later attempts). There was no free disk space when it failed, so I'm >>> assuming that was the cause. >>> 2) attempt on Windows with Couchdb 1.2.0 it failed with the error mentioned >>> below. The .compact file had around 50GB, there was plenty of free space >>> left on the disk. >>> 3) attempt on Ubuntu with Couchdb 1.5.0 it failed with the error mentioned >>> below. The .compact file had around 50GB, there was plenty of free space >>> left on the disk, and judging from the numbers present in the log (ids? >>> node numbers?) it failed at the same moment as attempt #2. >>> >>> Just wanted to make sure we're on the same page :) Do you still want me to >>> try it with an empty .compact file? (I can do this only during night hours, >>> since I don't want to put too much load on the server during working hours) >>> >>> Best regards, >>> Igor Klimer >>> ________________________________________ >>> Od: Robert Samuel Newson [[email protected]] >>> Wysłano: 10 stycznia 2014 14:03 >>> Do: user >>> Temat: Re: Error during compaction >>> >>> Hrm, strike one. Ok. Next thing to try is subtly different. stop couchdb, >>> delete the .compact file, but then make a new, empty .compact file (so >>> ’touch /path/to/dbname.compact’), start couchdb and compact. >>> >>> B. >>> >>> On 10 Jan 2014, at 12:42, Igor Klimer <[email protected]> wrote: >>> >>>> Yes, I've already done that after the very fist attempt at compaction (the >>>> one that failed because of lack of disk space). And it resulted in the >>>> second fail (on Windows), then the same on Linux - I always deleted the >>>> incomplete (about 50% of the database, around 50GB) .compact file before >>>> running the compaction again. So I was always doing compaction from >>>> scratch. >>>> >>>> Best regards, >>>> Igor Klimer >>>> ________________________________________ >>>> Od: Robert Samuel Newson [[email protected]] >>>> Wysłano: 10 stycznia 2014 13:08 >>>> Do: user >>>> Temat: Re: Error during compaction >>>> >>>> Thanks! that’s very useful. Hitting end of disk certainly feels like a >>>> cause here. Since the compaction has never completed, I suggest we redo >>>> compaction from scratch. >>>> >>>> 1) stop couchdb >>>> 2) delete (or move aside) the dbname.compact file for this database >>>> 3) start couchdb >>>> 4) compact the db >>>> >>>> Whether it works or not, please let us know. >>>> >>>> B. >>>> >>>> On 10 Jan 2014, at 08:25, Igor Klimer <[email protected]> wrote: >>>> >>>>>> Given that you’re at 100Gb and compacting for the first time, can you >>>>>> tell us if you were running on older couchdb versions that 1.2.0 between >>>>>> db creation and today? >>>>> >>>>> No, we've been running 1.2.0 from the start (around Oct 2012), then >>>>> switched to Ubuntu and 1.5.0. >>>>> >>>>>> Do you have free disk space? >>>>> Yes, there's about 150% of the DB's size worth of free space :) I forgot >>>>> to mention ("OK, here we go, the user will confess to some sin he >>>>> committed and is ashamed of and is most likely the reason for this >>>>> failure") that we've run the compaction once before the error on Windows >>>>> I mentioned below, but it failed because of insufficient disk space - so >>>>> I double checked before running the compaction again if there's enough >>>>> space. Here's the log, if it's any helpful: http://pastebin.com/S1URXN0p >>>>> Do you think it could have left the database in some corrupted state? It >>>>> seems it failed at a different part then the two next attempts (and, as >>>>> far as I understand, compaction is just copying over the database while >>>>> pruning the old revisions and deleted documents). >>>>> >>>>> Thank you for your time and help and best regards, >>>>> Igor Klimer >>>>> ________________________________________ >>>>> Od: Robert Samuel Newson [[email protected]] >>>>> Wysłano: 9 stycznia 2014 17:13 >>>>> Do: user >>>>> Temat: Re: Error during compaction >>>>> >>>>> Do you have free disk space? >>>>> >>>>> On 9 Jan 2014, at 15:25, Robert Samuel Newson <[email protected]> wrote: >>>>> >>>>>> >>>>>> Given that you’re at 100Gb and compacting for the first time, can you >>>>>> tell us if you were running on older couchdb versions that 1.2.0 between >>>>>> db creation and today? >>>>>> >>>>>> B. >>>>>> >>>>>> On 9 Jan 2014, at 14:39, Igor Klimer <[email protected]> wrote: >>>>>> >>>>>>> Hi all, >>>>>>> I've stumbled upon a peculiar problem while trying to compact (for the >>>>>>> first time) a large(-ish) database (~100GB at that time). At about 50% >>>>>>> it failed with this error: http://pastebin.com/qeaZNHMj >>>>>>> This is from Windows Server 2008 R2 Enterprise with Couchdb 1.2.0. >>>>>>> I figured that it might be a bug in the Windows build (Erlang on >>>>>>> Windows? C'mon, that can't be good ;)) or already fixed in a newer >>>>>>> version. Some time later we migrated the server to a Linux box running >>>>>>> Ubuntu 12.04.3 LTS (GNU/Linux 3.8.0-33-generic x86_64) and update >>>>>>> Couchdb to 1.5.0. >>>>>>> Unfortunately, the same error occurred: http://pastebin.com/feJWu7bN >>>>>>> >>>>>>> I've tried wrapping my head around that error, googling it, checking >>>>>>> this mail list but to no avail :) So if anyone can give me any pointers >>>>>>> as to what might be causing this problem, I'd be very grateful. >>>>>>> >>>>>>> Best regards, >>>>>>> Igor Klimer >>>>>>> >>>>>>> (sorry for the footer that will probably follow, unfortunately it's >>>>>>> added for all outgoing external mail...) >>>>>>> >>>>>>> >>>>>>> >>>>>>> > > > > > ------------------------------- > > getBACK S.A., ul. 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