230055 - IMAP connections don't get freed / no error message when unable to connect to IMAP

Status: RESOLVED WORKSFORME

(Thunderbird :: Mail Window Front End, defect)

Description

[Volker]

User-Agent:       Mozilla/5.0 (Windows; U; Windows NT 5.0; en-US; rv:1.6b) Gecko/20031114 Firebird/0.7+
Build Identifier: Mozilla/5.0 (Windows; U; Windows NT 5.0; en-US; rv:1.6b) Gecko/20031114 Firebird/0.7+

env server:
FreeBSD 4.9-RELEASE
Courier-IMAP 2.2.1/i386-unknown-freebsd4.9/Fri Dec 12 21:30:31 CET 2003
imapd *and* imapds (ssl)

env workstation 1:
Win98
Thunderbird 0.4 (release)

env: workstation 2:
Win2k
Thunderbird 0.5a (2003-12-23)

Same behaviour on both workstations:
Thunderbird connects to IMAP server. Tb is getting folder list and INBOX
messages. When clicking through the folder list (clicking one folder after
another) the message area doesn't get updated _after_ the 4th folder has been
read (clicked).
Back on an already read folder where the messages are well being displayed (one
of the 4 folders clicked after Tb launch) clicking on an already read message
makes the preview window displaying the message. When clicking on a new message
in that folder, sometimes doesn't get the message displayed. Even the message
source will stay empty.


Reproducible: Always

Steps to Reproduce:
1. see above
2. click through 4 folders
3. the 5th doesn't get listed messages

Actual Results:  
no message list (headers), no preview data (blank preview window), no folder
list update (on subfolders)

Expected Results:  
After closer inspection, I found the following:

On the server running courier-imap the UID for the requested mailbox has 4
imapd's running. They keep running until Tb is being closed. When kill'ing -15
any or all of these imapd's Tb works fine again.
Tb also works fine when using the Offline extension and setting Tb offline and
back again online after 4 folders have been read.

Now I found that courier-imapd comes with a default configuration of max 4
sessions per IP (etc/imapd: MAXPERIP=4). Tb defaults to 5 cached server
connections and does not close these connections until either Tb closes or it
exceeds the configured connections or is being set offline (using Offline
extension).

Setting Tb to max 3 or 4 connections works well even with courier-imap (in
default configuration; Tb 0.1 or 0.2 tested a while back and these versions
worked well with that courier-imap).

Tb doesn't even make it easy to solve because no error message is being displayed.

Tb has to inform the user with an error dialog saying "I'm unable to connect to
IMAP server (connection refused)" (or connect timed out or similar). An error
message would make (debugging) life a bit easier.



To resolve problems like these (no message header display, no message preview,
no folder update etc.):
1. reduce numer of cached connections to IMAP server (Tools -> Account Settings
-> Server Settings -> Advanced -> Maximum number of server connections to cache)
2. increase MAXPERIP configuration option on courier-imap
or
3. display an error message in Tb if it can't establish more than a few connections

Also, decrease the default value of IMAP max. connections to server or document
the configuration options.

I've found other users filing bug reports with similar behaviour but no one ever
gave a solution (so I'm filing this to give you one).

Comment 1

[Mike Patterson]

I can verify that this happens (perhaps unsurprisingly) with 0.5 under Mac OS X,
and 0.5b (28 Feb 2004 build) under Win32.

I tried increasing my MAXPERIP (also courier-imap, running under FreeBSD 5.2.1)
as suggested and it seems to work.  But it would have been nice if Thunderbird
could have told me "no more connections allowed" or something along those lines
- the silent failure was confusing.

I don't know if it has similar failure modes with other IMAP servers.

Comment 2

[Gordon Jahn]

I can confirm this on Mozilla 1.6, Gentoo Linux both PC and SPARC hardware so
it's probably ALL HW and ALL OS.

I only realised there was a max concurrent connections setting after reporting
this as a problem to the Courier IMAP list - I could see messages fine in
SqWebMail but not at all in Mozilla.

I too think the mail browser should have some form of error message when
connections to IMAP servers fail.

I did suggest on the Courier list that its default be 5 connections instead of 4
which wouldn't have led to any problems, but haven't had a response.

Comment 3

[Axel Bock]

I can still confirm that with TB trunk 0.6+, and it is really annoying.
At least the description of volker helps very much! This should be resolved or
given a warning message, because this error makes thunderbird look and feel very
unreliable, which it even isn't in this case.

Comment 4

[Axel Bock]

Ah - maybe this has another effect: if I browse my messages with TB, it
sometimes does not display all new messages in a folder. After some twiddling,
some time or some restarts those - definitely existing - messages sometimes just
appear. 

I double-checked the existance of those messages in the very filesystem folder,
and I let procmail copy every received message copy into a "copy folder", so I
really could be sure the messages in questeion are there and not displayed
(instead of not there *therefor* not displayed). this is feeling very
unprofessional and really should be taken care of in my opinion (activate voting
for bugs? :-))

Comment 5

[Avleen Vig]

I too had this problem after my wife switched from Outlook Express to TB.
The trouble is, courier doesn't *tell* TB that it won't accept more connections.
It just refuses to accept them.

The appropriate response should be "connection rejected" (rejected, because it
is accepted then closed, not outright refused.

Comment 6

[Chris Horry]

*** Bug 228344 has been marked as a duplicate of this bug. ***

Comment 7

[Simone Gianni]

In TB 0.6, setting maximum number of cached connections to IMAP server to 1 
fixed the problem, but something new happened : now new messages are counted 
twice. If i receive 3 messages TB writes "6 new messages". Also in the folders 
list there is a number which is doubled if compared with real new messages 
contained. When clicking on the folder the number suddenly changes to the 
correct one, since now TB reads the real headers from the folder and 
discards "cached" infos about the number of messages contained in it.

Comment 8

[Ashley Bischoff (blog at handcoding.com)]

Simone: You may be running into bug 239196 (which is now fixed). Try a more
recent build to see if that resolves your issue:
http://ftp.mozilla.org/pub/mozilla.org/thunderbird/nightly/latest-trunk/

PS Be sure to add yourself to the CC list when adding a comment, otherwise you
won't receive any replies ;).

Comment 9

[Dennis Jacobfeuerborn]

Thanks for making me a happy Thunderbird user finally as I was already
contemplating switching to another client. Having to relaunch Thunderbird every
3 or 4 folder clicks wasn't fun at all and reducing the number of cached
connections fixed this for me.
This should be a considered a showstopper for the next Thunderbird release.

Comment 10

[Ben Franske]

Same thing for me. I've been searching for a solution to this problem for a LONG
time now, glad I found this solution. This should be a major issue! Anyone
running IMAP with more than a few folders runs into this and it is really a drag
to close and restart TB every four folders which is the other fix. This problem
is ESPECIALLY hard to track down due to the lack of an error message. An error
message would be great, even better would be to lower the default connections as
well. I've also had problems with having a bunch of accounts on the same server
not work when accessed through a single client, perhaps this is the problem for
that as well!

Also, could someone change the OS to "All" and raise the severity? This is a big
problem for IMAP users!

Comment 11

[Gregory Bond]

Attachment: IMAP protocol trace (extracted from imapd truss output)

This is an IMAP protocol trace showing the bug on one of my emails.

Comment 12

[Gregory Bond]

um, ignore that attachment - was intended for another bug altogether, dunno why
bugzilla put me here!

Comment 13

[Ben Franske]

In Tb 1.0 I don't have to reduce the number of cached conncections. Everything
still seems to work at 5. Has this bug been squashed? Is anyone else still
having problems with the defualt configuration?

Comment 14

[David Klausner]

(In reply to comment #13)
> In Tb 1.0 I don't have to reduce the number of cached conncections. Everything
> still seems to work at 5. Has this bug been squashed? Is anyone else still
> having problems with the defualt configuration?

Yep, still problems.  I just installed the nightly, too.

Comment 15

[Wayne Mery (:wsmwk)]

fixed in FF 1.5?

David Klausner does problem happen in current nightly?

Comment 16

[David Klausner]

I don't see this in 1.5.

Comment 17

[Wayne Mery (:wsmwk)]

Comment on attachment 162642 [details]
IMAP protocol trace (extracted from imapd truss output)

obs per comment 12

Comment 18

[Wayne Mery (:wsmwk)]

WFM per comment 16