[horde] Problems with horde_autoloader_cache

[Jens Grüntjes]

Hello list,

I just installed the horde_autoloader_cache according to  
http://www.horde.org/apps/webmail/docs/PERFORMANCE#autoloading like  
this:

host # pear install horde/horde_autoloader_cache
horde/Horde_Autoloader_Cache can optionally use PHP extension "eaccelerator"
horde/Horde_Autoloader_Cache can optionally use PHP extension "xcache"
downloading Horde_Autoloader_Cache-2.1.0.tgz ...
Starting to download Horde_Autoloader_Cache-2.1.0.tgz (13,099 bytes)
.....done: 13,099 bytes
install ok: channel://pear.horde.org/Horde_Autoloader_Cache-2.1.0


Now, every five minutes I receive a mail with the following contents:

Cannot write Autoloader cache to backend.


The sender is the Cron daemon that calls the horde-alarms script. Here  
is the complete source of the mail:

Return-Path: <www-data at XXXXX.XXX.de>
Received: from deliver ([unix socket])
	 by boromir (Cyrus v2.4.16-Debian-2.4.16-4+deb7u1) with LMTPA;
	 Wed, 16 Apr 2014 13:20:19 +0200
X-Sieve: CMU Sieve 2.4
Received: from localhost (localhost [127.0.0.1])
	by XXX.XXXXXXX.de (Postfix) with ESMTP id B38D4206002
	for <www-data at XXXXXXX.XX.de>; Wed, 16 Apr 2014 13:20:19 +0200 (CEST)
X-Virus-Scanned: Debian amavisd-new at host.dmz
Received: from mail.ebira.de ([127.0.0.1])
	by localhost (XXXXX.XXXX.de [127.0.0.1]) (amavisd-new, port 10024)
	with ESMTP id lr8r9jHF8Fqr for <www-data at XXXXXX.XXXXXXXXXX.de>;
	Wed, 16 Apr 2014 13:20:10 +0200 (CEST)
Received: by XXXX.XXXXXXXXXXX.de (Postfix, from userid 33)
	id BB4E1206001; Wed, 16 Apr 2014 13:20:10 +0200 (CEST)
From: root at mail.ebira.de (Cron Daemon)
To: www-data at XX.XX.de
Subject: Cron <www-data at host> /usr/bin/horde-alarms
Content-Type: text/plain; charset=UTF-8
X-Cron-Env: <SHELL=/bin/sh>
X-Cron-Env: <HOME=/var/www>
X-Cron-Env: <PATH=/usr/bin:/bin>
X-Cron-Env: <LOGNAME=www-data>
Message-Id: <20140416112010.BB4E1206001 at XXX.XXXX.de>
Date: Wed, 16 Apr 2014 13:20:10 +0200 (CEST)

Cannot write Autoloader cache to backend.


I don't find anything in horde's log files (at level DEBUG). The only  
Google-hit with the mail content provides me with a link to github  
https://github.com/horde/horde/blob/master/framework/Autoloader_Cache/lib/Horde/Autoloader/Cache.php. I wonder why I don't see the log message in my  
logs.

I pruned the cache (horde-autoloader-cache-prune) and restarted the  
web server but no change. I'm using the APC cache, neither XCache nor  
eAccelerator is installed. It looks like a permission issue but where  
can I start looking?

--
Greetings
Jens