295640 - Client keeps open inactive IMAP connections causing server overload

Status: RESOLVED INVALID

(MailNews Core :: Networking: IMAP, defect)

Description

[andrew]

User-Agent:       Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.7.8) Gecko/20050511
Build Identifier: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.7.8) Gecko/20050511


We run UW imapd for several hundred users. After new Mozilla and Thunderbird
clients were deployed the server load became very high. The problem appears
to be that the client now defaults to opening a maximum of 5 IMAP streams, so that 
if a user browses several folders the number of connects will climb to 5 and
stay there until they disconnect - for some users on our internal LAN, perhaps
never (modulo power outages/software upgrades/ system crashes). We have
a mechanism to zap multi-day idle connects, but idle same-day connects
are a problem. We can ask users to change their settings, and we can kill
their connections, but it would be preferable if the client were to
automatically reduce the number of open connects when it is idle, as each forked
imapd process consumes system memory on the server

Reproducible: Always

Steps to Reproduce:
1.Connect to server
2.Do a lot of mail activity, opening multiple folders
3.Go to lunch leaving client running

Actual Results:  
Client leaves the maximum number IMAP connections open, possibly forever

Expected Results:  
Closed all the connections, possibly leaving one open if
automatic checking is enabled every minute.

Also in Mozilla Suite 1.7.7

Comment 1

[Dan Merillat]

I can confirm the same behavior on mozilla 1.7.12/mailnews.  Even if the user
closes the mailnews window, all IMAP connections remain open to all configured accounts.   The only way to close them is to file->quit and restart.  

Cached connections are nice while you're browsing mail, but after enough idle time they need to go away.   Especially if there's no action the user can take to get rid of them.

It's very rough on mailservers, especially with SSL/TLS.  Decrypting all the IDLE/NULL commands from hundreds of clients * 5 cached connections?

Comment 2

[David :Bienvenu]

we've always done that - you can reduce the number of connections we cache from 5 to 1, if you want, through the account settings | server | advanced button.

We only keep the connections open for 29 minutes - we assume the server will drop them after that. But we don't drop the connections - we leave that up to the server.

The user can go offline to kill the connections, by hitting the offline icon at the bottom left of the mail window.

Comment 3

[Joshua Cranmer [:jcranmer]]

IMAP networking problem.

Comment 4

[Joshua Cranmer [:jcranmer]]

INVA.