[Exim] locking question.

(exim 3.36)

Since starting to use exim I have occasionally experienced times where one
or another server will be unable to lock one of the hints databases
(usually retry). While it is inconvenient, it is not the end of the
world. I delete the db and the lockfile and the world moves on. Earlier
this week, however, several events occurred simultaneously and have made
this much more of an issue. The problems were two separate but equally
voracious spammers, the failure of our primary mail server, the above
mentioned locking problem occurring on our primary mailbagger, and yours
truly being out of town and uncontactable. The end result was a huge
number of _legitimate_ mail in queue on the mail bagger after the spam
had been identified and deleted.

So, this got me to wondering about the nature of locking for these hints
dbs. Almost everything in the docs refers to locking for appendfile
transport and so forth. Pretty much the only mention of locking and the
hints dbs is that it does occur. Looking at the source, it appears that
only fcntl locking is done. The file it locks is called .lockfile, but
the file doesn't seem to use true lockfile locking (hitching post creation
and whatnot).

This seems like an issue to me as our db directory is on NFS (a netapp
F760). In fact, the whole spool directory is on NFS, and has for the most
part worked beautifully. We have experienced in the past w/ flock times
where files on NFS will become unlockable - that is, not only does locking
not work, but it sort of permanently "freezes out" all locks on that
inode. fcntl in this case certainly appears to be doing the same thing,
which explains why removing the files (and thus generating new inodes)
works here. I had thought that problems like this were why exim
supported lockfiles so much, but I see in the book that it actually had
something to do with the size of the file reported by the NFS server. I
suppose if this is the reason lockfile wouldn't be viewed as necessary
because the file that gets locked contains no data itself.

Does anyone experience problems like this? Is there any chance of getting
lockfiles for hints dbs? I convinced my boss that exim was NFS/lockfile
clean when we moved to it, I would certainly hate to have to use local
storage now. Also, are there any other places where fcntl is used only?

Thanks
--John Jetmore