Stale NFS file handles on 8.x amd64

[Rick Macklem]

> I've been running dovecot 1.1 on FreeBSD 7.x for a while with a bare
> minimum of NFS problems, but it got worse with 8.x. I have 2-4 servers
> (usually just 2) accessing mail on a Netapp over NFSv3 via imapd.
> delivery is via procmail which doesn't touch the dovecot metadata and
> webmail uses imapd. Client connections to imapd go to random servers
> and I don't yet have solid means to keep certain users on certain
> servers. I upgraded some of the servers to 8.x and dovecot 1.2 and ran
> into Stale NFS file handles causing index/uidlist corruption causing
> inboxes to appear as empty when they were not. In some situations
> their
> corrupt index had to be deleted manually. I first suspected dovecot
> 1.2
> since it was upgraded at the same time but I downgraded to 1.1 and its
> doing the same thing. I don't really have a wealth of details to go on
> yet and I usually stay quiet until I do, and half the time it is
> difficult to reproduce myself so I've had to put it in production to
> get
> a feel for progress. This only happens a dozen or so times per weekday
> but I feel the need to start taking bigger steps. I'll probably do
> what
> I can to get IMAP back on a stable base (7.x?) and also try to debug
> 8.x
> on the remaining servers. A binary search is within possibility if I
> can reproduce the symptoms often enough even if I have to put a test
> server in production for a few hours.
> 
> Any tips on where we could start looking, or alterations I could try
> making such as sysctls to return to older behavior? It might be worth
> noting that I've seen a considerable increase in traffic from my mail
> servers since the 8.x upgrade timeframe, on the order of 5-10x as much
> traffic to the NFS server. dovecot tries its hardest to flush out the
> access cache when needed and it was working well enough since about
> 1.0.16 (years ago). It seems like FreeBSD is what regressed in this
> scenario. dovecot 2.x is going in a different direction from my
> situation and I'm not ready to start testing that immediately if I can
> avoid it as it will involve some restructuring.
> 
> Thanks for any input. For now the following errors are about all I
> have
> to go on:
> 
> Nov 29 11:07:54 server1 dovecot: IMAP(user1):
> o_stream_send(/home/user1/Maildir/dovecot/private/control/.INBOX/dovecot-uidlist)
> failed: Stale NFS file handle
> Nov 29 13:19:51 server1 dovecot: IMAP(user1):
> o_stream_send(/home/user1/Maildir/dovecot/private/control/.INBOX/dovecot-uidlist)
> failed: Stale NFS file handle
> Nov 29 14:35:41 server1 dovecot: IMAP(user2):
> o_stream_send(/home/user2/Maildir/dovecot/private/control/.INBOX/dovecot-uidlist)
> failed: Stale NFS file handle
> Nov 29 15:07:05 server1 dovecot: IMAP(user3): read(mail, uid=128990)
> failed: Stale NFS file handle
> 
> Nov 29 11:57:22 server2 dovecot: IMAP(user4):
> open(/egr/mail/shared/vprgs/dovecot-acl-list) failed: Stale NFS file
> handle
> Nov 29 14:04:22 server2 dovecot: IMAP(user5):
> o_stream_send(/home/user5/Maildir/dovecot/private/control/.INBOX/dovecot-uidlist)
> failed: Stale NFS file handle
> Nov 29 14:27:21 server2 dovecot: IMAP(user6):
> o_stream_send(/home/user6/Maildir/dovecot/private/control/.INBOX/dovecot-uidlist)
> failed: Stale NFS file handle
> Nov 29 15:44:38 server2 dovecot: IMAP(user7):
> open(/egr/mail/shared/decs/dovecot-acl-list) failed: Stale NFS file
> handle
> Nov 29 19:04:54 server2 dovecot: IMAP(user8):
> o_stream_send(/home/user8/Maildir/dovecot/private/control/.INBOX/dovecot-uidlist)
> failed: Stale NFS file handle
> 
> Nov 29 06:32:11 server3 dovecot: IMAP(user9):
> open(/egr/mail/shared/cmsc/dovecot-acl-list) failed: Stale NFS file
> handle
> Nov 29 10:03:58 server3 dovecot: IMAP(user10):
> o_stream_send(/home/user10/Maildir/dovecot/private/control/.INBOX/dovecot-uidlist)
> failed: Stale NFS file handle
>
Others have made good suggestions. One more you could try is disabling the negative
name caching by setting the option "negnametimeo=0". The addition of negative name
caching is also in FreeBSD7, but it is a fairly recent change, so your FreeBSD7 boxes
may not have had it. I also think trying the "dot-locking" and running without statd
and lockd (you can mount with the "nolock" option) would be worth trying. And, of course,
disabling attribute caching is mentioned on the web page others cited.

Good luck with it, rick
ps: Unfortunately the NFS protocol cannot support for POSIX file system semantics, so
    some apps can never run correctly on NFS mounted volumes. NFSv4 comes closer, but
    it still can't provide full POSIX semantics.