The issue is resolved. We did not see any bad side effects for the fix 
-> simply works.

Thank you.

Looking good so far, will provide final feedback next week

Thank you very much for your fast response. Will try the patch and report back

Changes have been made in Git (develop):

commit 0f8e19b5982e5d078195800a4e7af78b8956f893
Author: Michael M Slusarz <slusarz@horde.org>
Date:   Wed Feb 29 16:49:05 2012 -0700

     Bug #11041: If mailbox listing fails, this needs to be a fatal 
error since the IMAP tree cannot be built correctly.

  imp/lib/Imap/Tree.php |   15 ++++++---------
  1 files changed, 6 insertions(+), 9 deletions(-)

http://git.horde.org/horde-git/-/commit/0f8e19b5982e5d078195800a4e7af78b8956f893

Your tree object is very broken:

                     [_tree:protected] => Array
                         (
                             [base] => Array
                                 (
                                     [a] => 0
                                     [v] => base
                                 )

                             [vfolder] => Array
                                 (
                                     [a] => 385
                                     [c] => 0
                                     [p] => base
                                     [v] => vfolder
                                 )

                             [impsearchvinbox] => Array
                                 (
                                     [a] => 136
                                     [c] => 0
                                     [p] => base
                                     [v] => impsearchvinbox
                                 )

                         )

Namely, there is no INBOX value.  There HAS to be an INBOX value, and 
our code explicitly creates one if it doesn't exist.

Although looking at the code... if an exception is thrown from the 
Imap server, INBOX won't be added.  That shouldn't be that way - we 
need to fatal out if the IMAP server can't do a basic thing like 
listing mailboxes.  You can try applying this patch and see if you get 
an IMAP error now.

Changes have been made in Git (master):

commit 0f8e19b5982e5d078195800a4e7af78b8956f893
Author: Michael M Slusarz <slusarz@horde.org>
Date:   Wed Feb 29 16:49:05 2012 -0700

     Bug #11041: If mailbox listing fails, this needs to be a fatal 
error since the IMAP tree cannot be built correctly.

  imp/lib/Imap/Tree.php |   15 ++++++---------
  1 files changed, 6 insertions(+), 9 deletions(-)

http://git.horde.org/horde-git/-/commit/0f8e19b5982e5d078195800a4e7af78b8956f893

Attached is the output of our patch, diagnose_output.txt

Helo,

since upgrading to IMP 5.X we experience the following issue:

Sporadically one PHP process draws 100% CPU until it reaches 
max_execution_time. This happens > 10 times per day on a busy System 
serving >100k e-mail-accounts. php errorlog shows that the script 
reaches max_execution time while it is in different parts of 
imp/lib/Imap/Tree.php like this:

[27-Feb-2012 10:59:07] PHP Fatal error:  Maximum execution time of 300 
seconds exceeded in horde-git/imp/lib/Imap/Tree.php on line 1709

You can find more lines from the errorlog below.

strace on the process that draws 100% CPU does not show anything so 
not syscalls are executed.

Environment: PHP5.3.10, APC. (We got the same behaviour with 5.2.X and 
eaccelerator)

To further diagnose this issue we ran the attached patch 
("diagnose_patch.diff")

This will alert us if a certain loop in Tree.php gets executed 1.000 
times and save print_r of debug_backtrace to a file. We have verified 
at least one instance where this code gets triggered for a process 
that suffers from the 100% CPU problem and gets killed after reaching 
max_execution_time. You can find the output for this process in 
"daignose_output.txt".

As far as we can tell there seems to be loop in the code of Tree.php, 
specifically in getPollList: The foreach does not ever seem to exit in 
our case.

Unfortunately we do not know how to continue in solving this problem. 
Can you please point us into the right direction? We are willing to 
run more diagnostic code to further narrow down the root cause of this 
elusive problem.





Some output from php errorlog:

[27-Feb-2012 10:42:04] PHP Fatal error:  Maximum execution time of 300 
seconds exceeded in horde-git/imp/lib/Imap/Tree.php on line 829
[27-Feb-2012 10:43:13] PHP Fatal error:  Maximum execution time of 300 
seconds exceeded in horde-git/imp/lib/Imap/Tree.php on line 1708
[27-Feb-2012 10:44:19] PHP Fatal error:  Maximum execution time of 300 
seconds exceeded in horde-git/framework/Prefs/lib/Horde/Prefs.php on 
line 317
[27-Feb-2012 10:44:41] PHP Fatal error:  Call to a member function 
getName() on a non-object in horde-git/imp/lib/Ajax/Application.php on 
line 1349
[27-Feb-2012 10:44:52] PHP Fatal error:  Maximum execution time of 300 
seconds exceeded in horde-git/imp/lib/Imap/Tree.php on line 1827
[27-Feb-2012 10:45:11] PHP Fatal error:  Maximum execution time of 300 
seconds exceeded in horde-git/imp/lib/Imap/Tree.php on line 1827
[27-Feb-2012 10:45:52] PHP Fatal error:  Maximum execution time of 300 
seconds exceeded in horde-git/imp/lib/Imap/Tree.php on line 1676
[27-Feb-2012 10:45:54] PHP Fatal error:  Maximum execution time of 300 
seconds exceeded in horde-git/imp/lib/Imap/Tree.php on line 1827
[27-Feb-2012 10:45:59] PHP Fatal error:  Maximum execution time of 300 
seconds exceeded in horde-git/imp/lib/Imap/Tree.php on line 1279
[27-Feb-2012 10:46:00] PHP Fatal error:  Maximum execution time of 300 
seconds exceeded in horde-git/imp/lib/Imap/Tree.php on line 1709
[27-Feb-2012 10:46:04] PHP Fatal error:  Maximum execution time of 300 
seconds exceeded in horde-git/imp/lib/Imap/Tree.php on line 1277
[27-Feb-2012 10:46:07] PHP Fatal error:  Maximum execution time of 300 
seconds exceeded in horde-git/imp/lib/Imap/Tree.php on line 1709
[27-Feb-2012 10:46:07] PHP Fatal error:  Maximum execution time of 300 
seconds exceeded in horde-git/imp/lib/Imap/Tree.php on line 1709
[27-Feb-2012 10:46:15] PHP Fatal error:  Maximum execution time of 300 
seconds exceeded in 
horde-git/framework/Prefs/lib/Horde/Prefs/Scope.php on line 138
[27-Feb-2012 10:46:16] PHP Fatal error:  Maximum execution time of 300 
seconds exceeded in horde-git/imp/lib/Imap/Tree.php on line 1277
[27-Feb-2012 10:51:09] PHP Fatal error:  Maximum execution time of 300 
seconds exceeded in horde-git/imp/lib/Imap/Tree.php on line 1277
[27-Feb-2012 10:51:11] PHP Fatal error:  Call to a member function 
getName() on a non-object in horde-git/imp/lib/Ajax/Application.php on 
line 1349
[27-Feb-2012 10:54:41] PHP Fatal error:  Call to a member function 
getName() on a non-object in horde-git/imp/lib/Ajax/Application.php on 
line 1349
[27-Feb-2012 10:57:34] PHP Fatal error:  Call to a member function 
getName() on a non-object in horde-git/imp/lib/Ajax/Application.php on 
line 1349
[27-Feb-2012 10:58:45] PHP Fatal error:  Maximum execution time of 300 
seconds exceeded in horde-git/imp/lib/Imap/Tree.php on line 1827
[27-Feb-2012 10:58:50] PHP Fatal error:  Maximum execution time of 300 
seconds exceeded in horde-git/imp/lib/Imap/Tree.php on line 1826
[27-Feb-2012 10:59:07] PHP Fatal error:  Maximum execution time of 300 
seconds exceeded in horde-git/imp/lib/Imap/Tree.php on line 1709