From Bugzilla Helper: User-Agent: Mozilla/5.0 (Windows; U; WinNT4.0; en-US; rv:0.9.2+) Gecko/20010723 BuildID: 2001072303 During normal operation, Mozilla seems to open more and more IMAP connections to the same server. My default courier-IMAP installation limited me to 4 connections/IP, which caused a "server refused connection" error to pop up. After raising that to 6, I still get the same message. This error may be related to 87825 Reproducible: Always Steps to Reproduce: 1.Define an IMAP account to a server running courier-imap in default config. 2.Define several folders 3.switch between them. Alternatively 1. Define several IMAP accounts to the same server running courier-IMAP. 2. Switch between them. Actual Results: An error message saying "The server refused connection" poped up on some of the folders (it seems that once a certain folder uses a certain folder, that folder will continue to work). Expected Results: I should be able to use an IMAP client with one connection only.
Status: UNCONFIRMED → NEW
Ever confirmed: true
Problem also happens under Linux BuildID: 2001082606 Playing around with IMAP, opening a few folder, having "check for new messages on", etc, it doesn't take long to get "connection refused" messages when the IMAP server (Courier-IMAP in this case) starts rejecting new connections because you have the maximum allowed 4 open. tcp 0 0 194.100.xx.85:1428 194.100.xx.82:993 ESTABLISHED tcp 0 0 194.100.xx.85:1432 194.100.xx.82:993 ESTABLISHED tcp 0 0 194.100.xx.85:1433 194.100.xx.82:993 ESTABLISHED tcp 0 0 194.100.xx.85:1434 194.100.xx.82:993 ESTABLISHED (IMAP-over-SSL in this example). For more details see the original bug report.
Using 0.9.4 under Linux and Windows, I was able to open 10 or more folders on a Courier-IMAP server (version 1.3.11) and the number of connections reported by the server topped out at 5. This seems consistent with my reading of mailnews/imap/src/nsImapIncomingServer.cpp -- in the CreateImapConnection method, maxConnections defaults to a hard-coded value of 5. Courier-IMAP does indeed default to a maximum of 4 connections per IP, so in the default case this'll cause problems for mozilla users with multiple folders. It also looks like there's a per-server preference to control this ("max_cached_connections"), but you probably have to edit your prefs file manually to set this.
I have this problem on the 10/1 MacOS 9.x build as well. Beefing up Courier-imap to handle a lot more connections solved the problem although it seems to be bad form for Mozilla to be so connection hungry. Combined with bug 87825 (related?), this does beat up on Mail's IMAP usefulness. I was testing this out on N4.7, and it played well with my Courier-IMAP server at its default setting.
Summary: Number of IMAP connections open is not limited → Courier-IMAP: Number of IMAP connections open is not limited
as a server writer, i don't find 5 concurrent connections to an IMAP server all that outrageous, especially since each new connection may incur a new TLS negotiation (hopefully session resumption, but who knows) and a possibly expensive authentication. i think the default courier limit is really a little silly.
OK, Courier imap only allows by default 4 connections from any IP address (or 40 in total from any IP). Now mozilla makes 5 connections by default. This isn't so bad if Mozilla noticed the connection refused and just used its existing connections. But what does it do!... When it tries to connect the 5th (the 5th folder browsed) courier immediately closes the connection and it seems mozilla just sits there like a muppet waiting for data on the closed socket. (There is a full connection establishment and teardown, i.e. ============================ Mozzie courier ============================ Syn----------------> <--------------- Syn, Ack Ack----------------> : 31 microseconds : <--------------- Fin, Ack Fin, Ack-----------> <--------------- Ack So mozzie has returned from connect() and is doing a read() which should return 0. However Mozzie seems to continue to try and read (forever) from this closed socket. ) From this point on you can not browse any new folders (you can browse 4 first folders you opened as these connections are still OK). I.E. you need to restart mozilla to get to other folders. Note a handy way to see the connections from mozzie is: watch -n1 'netstat -tan | grep 143' My build ID is 2001112012 (on Linux).
I agree with Chad_House, where he says: <quote>" It also looks like there's a per-server preference to control this ("max_cached_connections"), but you probably have to edit your prefs file manually to set this."</quote> However, when mozilla finds the server rejecting the Nth connection, it should auto-adjust back and reuse the avaialbe connections if possible. The current behaviour, as described by Padraig@AnteFacto.com doesn't particularly help. This is NOT Courier specific, of course ;)
Using 0.9.9 under Linux and Windows, Courier-IMAP server (version 1.4.3). Setting courier to 5 rather than 4 connections per IP allows connections to more than 5 folders (using a single account) , but if you have try to access folders in multiple accounts you seem to be limited to the first 5 or 6 folders again. If this means having to raise courier's connections per IP setting to (5 * # of accounts), on a shared PC this could be a large number. Going offline and online again resets the situation.
*** Bug 112692 has been marked as a duplicate of this bug. ***
Just noticed 71792 fixed today, which basically gives a configuration option for number of connections to "cache". I think this bug is a dup of it?
I'm still having this problem in 1.0: Using multiple accounts: Moving messages around in uw-imap, and Exchange imap works fine, but when I move a message in my courier imap, I can't see the result. Ex: Move message from Inbox --> Shared.notices.alerts I have to go offline and then online again before I can see the message in alerts (it does get moved)
Bug persists in Mozilla 1.1-final. Still getting disconnects from Courier-IMAP because Mozilla has too many connections open and does not recycle them. Is there a leak somewhere?
Why do Mozilla need to open several simultaneous sessions at all? I have a lot of mailboxes I wish to monitor for new mail, and this behaviour increases the server a lot. I would be very glad to hear why Mozilla does this! Can perhaps IMAP IDLE help? Or does it need fixing?
*** Bug 89583 has been marked as a duplicate of this bug. ***
This bug seems to persist in 1.2 beta. I still have to use the online/offline trick to view CourierImap folders if I view too many folder in one session.
is the situation still the same with a newer build? (bug cleaning)
I don't think this bug is an issue anymore ... now that you can limit the number of connections in your preferences it really isn't an issue with Mozilla but with IMAP servers that don't handle requests for connections over their limit in a responsible manner (e.g. Courier-IMAP). It doesn't seem like the number of accounts affects the number of connections opened anymore. Though maybe people want to keep it open to address a specific issue. In that case it should probably be retitled to reflect what that issue is. I'm using 1.4rc1 with mulitple accounts I am able to open a series of folders and copy back and forth between different accounts. I'm using Exchange 5.5 and Courier-IMAP, both of which seemed to cause problems previously.
dup of 71792 - you can limit the number of connections we'll cache (though we limit the low number to two - instead, we should probably limit it to 1) *** This bug has been marked as a duplicate of 71792 ***
Status: NEW → RESOLVED
Last Resolved: 15 years ago
Resolution: --- → DUPLICATE
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