Is using Berkeley DB 4.0.14 recommended?

[Aidan Evans]

On Thu, 17 Oct 2002 at 09:10 Rob Siemborski wrote to Mark Keasling and Info...

>On Thu, 17 Oct 2002, Mark Keasling wrote:
>
>> I'm trying to use Berkeley DB 4.0.14 and am getting the dreaded
>>   DBERROR db4: 4 lockers
>> messages even when only starting up the master process.  From
>> what I've seen reported, the lockers number will only increase and
>> cyrus will eventually start failing.
>
>DB4.0 has a known (cosmetic) bug that causes this number to monotonicly
>increase (they apparently are missing a decrement).  So as long as it is
>only increasing at a slow rate and you aren't seeing any other problems,
>all is well with the world.
>
>I don't believe any recent version of cyrus has a major Berkeley DB
>locking problem.  Of course, we also recommend using the skiplist backend
>for the mailboxes.db file.

  What Berkeley DB is CMU using?  I assume this is on Solaris, so it may
not be safe to compare to use on Linux.  Whatever version it is, it
certainly sounds as though it works for CMU.

  As I understand it, "DBERROR db4: ... lockers" messages occur when it
actually happens that a process has to wait for a lock.  Thus a small
number of occurrences relative to the amount of mail processed is nothing
to worry about.

  What seems to be a problem is the number of lockers gettting as high as
the maximum allowed, regardless of whether there is waiting for locks or
not.  If you don't have a big volume of mail it may take a long time for the
number to get too big.  If you also reboot frequently enough the number may
never get too big.

  My experience with DB 4.0.14 on RedHat Linux 7.2 is two instances of
complete failure of deliver.db and tls_sessions.db (and consequently all
Sieve processing) when the number of lockers reached 50,000, both instances
after about a week to ten days up time.  I expect a third failure if I let
the number of lockers get that high again.

Aidan Evans   | Networks & Systems
(902)494-3332 | University Computing & Information Services
              | Dalhousie University, Halifax, N.S., Canada