[imp] problems with large numbers of mailboxes

[Michael M Slusarz]

Quoting Scott Dellinger <scott.dellinger at uvm.edu>:

> I am finding that users with large numbers of mailboxes (somewhere  
> over about 577, but larger numbers like 800, consistently) are not  
> working correctly in IMP 5.0.17.  In the dynamic view, the page  
> loads ok but any subsequent request results in the user being logged  
> out on the server (as seen in the logs) and the user receives an  
> error about communicating with the server.  A subsequent click  
> returns the user to the login page.  In the traditional view (which  
> we?re not using, but I tested for this), the mailbox list is never  
> displayed, I see the user logout in the server log, and the first  
> click on anything results in a redirect to the login page.
>
> A couple of us have mass-created mailboxes so we could test this,  
> and it seems consistent for us (creating lots of mailboxes leads to  
> the user having the issue, removing them makes it go away).  If I  
> enable IMAP debugging, the session looks pretty ordinary when  
> compared with that of a user with a smaller number of mailboxes  
> during initial login, but no commands get sent following that.   
> During some debugging, I saw that in imp/lib/Ajax/Application.php?s  
> showMessage() function, which gets called when a user clicks a  
> message, the line:
>
> 	$GLOBALS['injector']->getInstance('IMP_Factory_Imap')->create()->openMailbox($this->_mbox, $rw ? Horde_Imap_Client::OPEN_READWRITE :  
> Horde_Imap_Client::OPEN_AUTO);
>
> never returns, so I?m presuming this means something has gone awry  
> with the IMAP session.

What does your CPU usage look like?  Do you have PHP processes using  
100% - this would indicate a bug in the code.

> Any ideas on what could be happening, before I start delving into IMAP code?

Not really, unfortunately.  Although one thing to look out for is if a  
user is polling all mailboxes.  This can absolutely slam a server.   
IMAP wasn't originally created to deal with this issue (although  
server-side mailbox caching and a server that implements LIST-STATUS  
helps immensely).

michael

___________________________________
Michael Slusarz [slusarz at horde.org]