[Akonadi] [Bug 339561] New: Imap resource uses multiple connections which causes problems with uw-imapd

[Jan Hudec]

https://bugs.kde.org/show_bug.cgi?id=339561

            Bug ID: 339561
           Summary: Imap resource uses multiple connections which causes
                    problems with uw-imapd
           Product: Akonadi
           Version: 1.13.0
          Platform: Debian testing
                OS: Linux
            Status: UNCONFIRMED
          Severity: minor
          Priority: NOR
         Component: IMAP resource
          Assignee: chrigi_1 at fastmail.fm
          Reporter: bulb at ucw.cz
                CC: kdepim-bugs at kde.org, vkrause at kde.org

I have mail on server which has crappy old uw-imapd. It works mostly fine as
long as only one connection is made, but when multiple connections are opened,
they tend to end with

    S: * BYE Killed ( lost mailbox lock )

and the operations requested are _not_ carried out.

Kmail up to 4.4 worked OK, but since the switch to Akonadi it always creates
one persistent connection and _another_ connection when it synchronizes. The
result is that status flags don't get written back and deleted mail reappears
after next synchronization.

The server exhibits this problem whenever I connect any two IMAP clients at
once, but with Aconadi it exhibits it even when only one is connected,
apparently because of the two concurrent connections.



Reproducible: Always

Steps to Reproduce:
The multiple connections should be readily observable. Just list connections
(e.g. with netstat) while kmail is doing synchronization.

The behaviour with uw-imapd requires an uw-imapd server serving from mbox
(spool is by default mbox, so e.g. with INBOX serving /var/mail/$USER directly)
with non-trivial amount of mail. Then try marking some mail as read, deleted
etc.

Actual Results:  
Multiple connections to the server exist.

With uw-imapd server with mbox mailbox changes mail reverts to previous state
on next synchronization. When logging is enabled (via KIMAP_LOGFILE
environment), many logs are created, most of them ending with

    S: * BYE Killed ( lost mailbox lock )

Expected Results:  
Only one connection exists.

uw-imapd works as long as not used by multiple clients at the same time.

The problem is really that uw-imapd is crap when serving mail from mbox files.
A workaround would be to switch to mbx files (I have shell access, I can
convert my mailboxes), but that would cause problems when the server gets
eventually switched to anything more sensible as dovecot doesn't support mbx
(and uw-imapd does not support maildir) and somewhat complicated as procmail
does not support it either. The other workaround is to create mirror with
offlineimap (I've already tried, it works, but uses a lot of memory) or isync.

I am marking this minor, because it appears to only cause problems to uw-imap,
which has been discontinued from Debian since ages and it's not clear whether
it is even supported upstream any more. IMAP is supposed to handle multiple
connections. Still it seems to me one connections should be sufficient and
clients that don't make multiple connection seem to work just fine with that
server.

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