dovecot - Jul 2009 - troubles with broken clients (iPhone) - again

The PC (Outlook) is accessing the mailbox via POP3, the iPhone is using 
IMAP; please consider we are talking about a user's home setup, so it's 
pretty difficult to have a more detailed report on his part (Outlook 
version, iPhone OS version, xDSL router type and configuration, etc.). The 
mail server 'dovecot -n' output is attached.

The symptoms: when the Mail application is "closed" on the iPhone,
Outlook
still says the mailbox is in use; a Dovecot imap process is still active 
for that user even after a few minutes (manually killing it releases the 
lock, thereby leaving the inbox available for Outlook).
>From the client side, there is a seemingly relevant article at
 	http://blogs.sun.com/chienr/entry/iphone_supports_imap_idle

it describes, among others, the "Settings / Mail / Auto-Check" and 
"Settings / General / Auto-Lock" parameters; from my point of view, 
however, being able to solve the problem directly on the server would be 
far better, and might also accomodate other broken clients we haven't seen 
yet: that's why I asked you whether there is a way to tell Dovecot only 
one POP3 or IMAP process from the same user, the latest one, can be active 
at the same time, closing and disconnecting all the others.

Regards, and thanks a lot again for your help

 	 		Federico Bianchi
 			Dipartimento di Storia delle Arti
 			Universita` di Pisa
 			piazza S.Matteo in Soarta, 2 - I56127 Pisa (Italy)
 			fax.+39-050-580128; e-mail: <f.bianchi at arte.unipi.it>
 			================================================== 			!DISCLAIMER!: my
e-mail reflects _my_own_ opinions!
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Le 7 juil. 09 ? 10:02, Federico Bianchi a ?crit :
>
> The PC (Outlook) is accessing the mailbox via POP3, the iPhone is  
> using IMAP; please consider we are talking about a user's home  
> setup, so it's pretty difficult to have a more detailed report on  
> his part (Outlook version, iPhone OS version, xDSL router type and  
> configuration, etc.). The mail server 'dovecot -n' output is
attached.
>
> The symptoms: when the Mail application is "closed" on the
iPhone,
> Outlook still says the mailbox is in use; a Dovecot imap process is  
> still active for that user even after a few minutes (manually  
> killing it releases the lock, thereby leaving the inbox available  
> for Outlook).
>
>> From the client side, there is a seemingly relevant article at
>
> 	http://blogs.sun.com/chienr/entry/iphone_supports_imap_idle
>
> it describes, among others, the "Settings / Mail / Auto-Check"
and
> "Settings / General / Auto-Lock" parameters; from my point of
view,
> however, being able to solve the problem directly on the server  
> would be far better, and might also accomodate other broken clients  
> we haven't seen yet: that's why I asked you whether there is a way
> to tell Dovecot only one POP3 or IMAP process from the same user,  
> the latest one, can be active at the same time, closing and  
> disconnecting all the others.
Hello Frederico,

Thanks for the additional info.

The output of dovecot -n doesn't show mbox_write_locks nor  
mbox_read_locks; it could thus be supposed that the locking methods in  
use are:

	mbox_write_locks = dotlock fcntl
	mbox_read_locks = fcntl

The question is now "who delivers mail to the mailboxes?"; since  
killing the last imap process allows the pop client to open the  
mailbox, one may suspect a deadlock involving the imap and the  
delivery processes.

Could you have a look at

	http://wiki.dovecot.org/MailboxFormat/mbox
	http://wiki.dovecot.org/MboxLocking

HTH,
Axel

On Tue, 2009-07-07 at 10:02 +0200, Federico Bianchi
wrote:
> The symptoms: when the Mail application is "closed" on the
iPhone, Outlook
> still says the mailbox is in use; a Dovecot imap process is still active 
> for that user even after a few minutes (manually killing it releases the 
> lock, thereby leaving the inbox available for Outlook).
That's strange. Normally an IMAP process shouldn't be holding any locks
at all. Can you check if there are any *.lock files that get deleted
when killing the imap process?
> that's why I asked you whether there is a way to tell Dovecot only 
> one POP3 or IMAP process from the same user, the latest one, can be active 
> at the same time, closing and disconnecting all the others.
No.
> pop3_lock_session(pop3): yes
This means that during the whole POP3 session Dovecot locks the mailbox
by creating dovecot-uidlist.lock. If it can't, it gives the "mailbox is
in use" error. So I could understand if there was a long-running pop3
process holding the lock, but imap processes really shouldn't be doing
that..
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On Tue, 7 Jul 2009, Timo Sirainen wrote:
> On Tue, 2009-07-07 at 10:02 +0200, Federico Bianchi wrote:
>> The symptoms: when the Mail application is "closed" on the
iPhone, Outlook
>> still says the mailbox is in use; a Dovecot imap process is still
active
>> for that user even after a few minutes (manually killing it releases
the
>> lock, thereby leaving the inbox available for Outlook).
>
> That's strange. Normally an IMAP process shouldn't be holding any
locks
> at all. Can you check if there are any *.lock files that get deleted
> when killing the imap process?
>
>> that's why I asked you whether there is a way to tell Dovecot only
>> one POP3 or IMAP process from the same user, the latest one, can be
active
>> at the same time, closing and disconnecting all the others.
>
> No.
>
>> pop3_lock_session(pop3): yes
>
> This means that during the whole POP3 session Dovecot locks the mailbox
> by creating dovecot-uidlist.lock. If it can't, it gives the
"mailbox is
> in use" error. So I could understand if there was a long-running pop3
> process holding the lock, but imap processes really shouldn't be doing
> that..
In fact - that's what puzzled me.

To have a simpler test case, this afternoon I upgraded Dovecot to the 
latest release leaving only the mbox storage (we are planning to convert 
to maildir in September) and, even if I don't think there is any relation 
with our issue, set that server MTA (Exim 4.69) to use both fcntl and dot 
lock files.

The user who got the bizarre situation should be back in a few days; 
should the problem be still there, I'll sure tell you all.

Thanks a lot again; regards

 	 		Federico Bianchi
 			Dipartimento di Storia delle Arti
 			Universita` di Pisa
 			piazza S.Matteo in Soarta, 2 - I56127 Pisa (Italy)
 			fax.+39-050-580128; e-mail: <f.bianchi at arte.unipi.it>
 			================================================== 			!DISCLAIMER!: my
e-mail reflects _my_own_ opinions!
 			===================================================