dovecot - Sep 2010 - Dovecot 2.0.1 Quota dict timeout

Since an upgrade to 2.0.1 from 1.2.x we're seeing this on (mostly)
large mailboxes (Maildir)

Sep  4 11:27:25 dovecot: dict: mysql: Connected to 192.168.dd.dd (accounts)
...
Sep  4 11:27:46 kelly-a dovecot: lda(u1 at example.com):): msgid=<123 at
xxx>:
saved mail to INBOX
Sep  4 11:27:47 dovecot: dict: Error: sql dict: commit failed: Not
connected to database
Sep  4 11:27:47 dovecot: imap(u1 at example.com): Error: dict quota: Quota
update failed, it's now desynced

The dict is MySQL on another server, same switch.  It does appear that
the quota gets out of sync. From the entries I checked an email is often
being delivered shortly before the error (as above). But I also see it
happen with the lda:

Sep  4 08:27:11 dovecot: pop3(u2 at example.com): Disconnected: Logged out...
Sep  4 08:42:48 dovecot: lda(u2 at example.com): msgid=<123 at aaa>: saved
mail to INBOX
Sep  4 08:43:26 dovecot: lda(u2 at example.com): msgid=<123 at bbb>: saved
mail to INBOX
Sep  4 08:43:26 dovecot: dict: Error: sql dict: commit failed: Not
connected to database
Sep  4 08:43:26 dovecot: lda(u2 at example.com): Error: dict quota: Quota
update failed, it's now desynced
Sep  4 08:46:14 dovecot: pop3-login: Login: user=<u2 at example.com>,...

This is happening on two different dovecot servers. The only thing they
share is the MySQL server, but it has a load of 0.5 at peak.

Is there something that can be tuned to keep this from happening?

Possibly relevant entries from `doveconf -n`. Any tuning regarding dict
can be assumed as default:

maildir_very_dirty_syncs = yes
mail_plugins = quota
plugin { quota = dict:user:%LTd-%LTn:proxy::quota }

Thanks!

David

On Sat, 2010-09-04 at 12:17 -0700, David Jonas wrote:
> Sep  4 11:27:47 dovecot: dict: Error: sql dict: commit failed: Not
> connected to database
Hmm. dict process thinks that all of its SQL connections are in use.
Although why that happens is slightly strange, because unless you
changed the defaults one process can handle only a single client
connection at a time, and normally one client wouldn't be sending
multiple requests simultaneously.

There is anyway a potential problem with an asynchronous SQL query not
being finished when a synchronous SQL query is started. Although that's
a problem only with PostgreSQL, not MySQL. Anyway, should be fixed some
day..

Well, see if this helps:
http://hg.dovecot.org/dovecot-2.0/rev/902f008f17cf