[horde] Automatically get logged out

[Thomas Trethan]

Hi,

I sometimes have a strange problem: my users get logged out  
automatically after a short while. When logging in, I can work as  
usual, then after some minutes (about 5-10, differs) I simply get  
logged out, beeing redirected to the login page saying something like  
"session timed out". The horde.log says nothing special:

2017-06-23T07:18:37+02:00 NOTICE: HORDE [horde] Login success for  
thomas to horde [pid 15382 on line 164 of "/usr/share/horde/login.php"]
2017-06-23T07:18:37+02:00 NOTICE: HORDE [imp] Login success for thomas  
to {imap://localhost/} [pid 15382 on line 157 of  
"/usr/share/horde/imp/lib/Auth.php"]
...
2017-06-23T07:25:25+02:00 NOTICE: HORDE [horde] User thomas logged out  
of Horde [pid 14509 on line 107 of "/usr/share/horde/login.php"]

In between login/logout other logins/logouts happen, by other users or  
by myself via activesync/smartphone.

The problem occurs every now and then. If it happens, it is  
reproduceable every time, but if its not happening, I can't force to  
reproduce it and Horde runs smoothly. My current solution is to  
restart Apache, then everything works fine again. I think there might  
by a session problem somewhere, and I think it's more an Apache than  
Horde related problem, but I don't know why yet.

Anyone experiencing similar troubles? Anyone ideas?
My next steps would be to set Horde log level to DEBUG and eventually  
hack the code...

I use Debian Jessie (8.8) with Apache 2.4.10 (https), PHP 5.6.30,  
MySQL 5.5.55, Horde 5.2.15, courier-imap-ssl for auth - all up to date.

Appreciate any suggestions,
thanks in advance,
Tom