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===================================================
Horde Groupware Webmail Edition Performance Guide
===================================================
:Contact: horde@lists.horde.org
.. contents:: Contents
Some tips on performance tuning systems for Horde Groupware Webmail Edition.
This does not cover hardware tuning or even low level system (network,
filesystem, etc) tuning.
Don't apply the following tuning hints blindly. Test your applications before
and after the changes under the conditions that are important for you. For
some people it's more important to make them as fast as possible for a small
user base, others require the applications to scale well under a high load.
Some of these hints might even make the applications slower under certain
conditions or using a certain hardware.
Linux Tuning
============
* Recompile RPMS for your architecture (e.g. i586, i686, athlon, etc).
This applies most to your Apache, PHP, IMAP, and POP3 packages.
Webserver/PHP tuning
====================
* Consider a PHP accelerator program. See for example `The Zend Performance
Suite`_, the `Alternative PHP Cache`_, eAccelerator_, or XCache_. These
accelerators speed up access by caching the compiled PHP code, eliminating
the need to recompile the code for every single page load. **This is probably
the easiest way to improve the performance of Horde Groupware Webmail
Edition**. See Autoloading_ further down to get even more out of some of
those accelerators.
* Enable PHP output compression in the Horde configuration. Do not enable
compression in the PHP configuration (i.e. in ``php.ini``), because certain
scripts don't work well with compression and Horde Groupware Webmail Edition
takes care of disabling compression conditionally.
* Keep the include path defined in ``php.ini`` as short as possible, with the
most frequently used library paths first. You don't need to include the
local directory ``.`` because Horde Groupware Webmail Edition always uses
full paths instead of relative paths.
* Use an optimized ``php.ini``: start with ``php.ini-recommended`` in your PHP
dsitribution.
* Don't run PHP session garbage collection too often if using a slow storage
medium (like SQL). (See ``session.gc_probability`` in ``php.ini``)
* If you have a large number of sessions and are using PHP's default file
based session handler, consider storing them in hashed directory levels.
(See ``session.save_path`` at http://www.php.net/session)
* Consider using a faster storage medium for sessions, such as a tmpfs
(if storing sessions locally) or memcache (for storing session information
that can be accessed by multiple servers).
* Only load as many Apache and PHP extensions as needed (to reduce memory
usage).
* Use statically compiled Apache modules, including the PHP module.
* Use compiler optimizations (--prefer-non-pic, -O3, -march -mcpu, -msse,
-mmmx, -mfpmath=sse, etc.)
* If using SSL with a large site, consider a hardware SSL accelerator.
* Use shared memory for the Apache SSL cache if possible.
* To improve caching of static content if accessing Apache SSL with Internet
Explorer, try setting longer expiration periods::
ExpiresActive On
ExpiresByType image/png "now plus 1 month"
ExpiresByType image/gif "now plus 1 month"
ExpiresByType text/javascript "now plus 1 month"
ExpiresByType application/x-javascript "now plus 1 month"
ExpiresByType text/css "now plus 1 month"
.. Note:: You must compile the ``mod_expires`` extension into Apache in
order to use these directives.
.. Warning:: This might cause problems if you upgrade Horde Groupware
Webmail Edition and the users' browsers still use the old file
versions.
* Disable DNS lookups in your Apache logging, or use a caching DNS server on
the web server host.
Horde itself will run DNS queries too, so make sure your DNS resolution works
correctly and fast.
* Enable Apache keepalives.
* You can configure Horde to serve all images, style sheets and/or static
javascript files from a different server. This could be a very lightweight
server without PHP (and other CGI modules) builtin. If using SSL to serve
all pages, the images/js server will also have to serve SSL content or else
browsers will complain about non-secure content in a secure page. Since this
server does not need to handle dynamic content, it would be wise to use a
high-performance server with low memory and/or system resource requirements
(this `IBM Article`_ can provide further information). You need to set
the ``themesuri`` and/or ``jsuri`` parameters in ``config/registry.php`` for
all applications and copy all ``themes`` and/or ``js`` directories in the
same directory layout to the other server.
* Your webserver should use Expires headers to make sure static content can
be cached on the user's browser. For example, to make lighttpd set an
expiration date on all graphics, javascript files, and stylesheets, add
the following to ``lighttpd.conf``::
$HTTP["url"] =~ "\.(jpg|gif|png|js|css)$" {
expire.url = ( "" => "access 1 months" )
}
* Enable caching in Horde Groupware. Several applications make heavy use of
caching and, if enabled, you will see a significant increase in performance.
* Enable caching/compression of javascript and CSS. See `Yahoo's Analysis`_
which concludes that "[r]educing the number of HTTP requests has the biggest
impact on reducing response time". Caching via filesystem is HIGHLY
RECOMMENDED: it is also the only way of caching that reliably works on all
browsers. Caching can also be done via horde caching, but the
cache-busters used to generate unique URLs when the cached content changes
do not work 100% reliably across all browsers.
* It is highly recommended to install the lzf PECL module to activate
compression for certain Horde data (especially in IMP). lzf is a tiny
module that does real-time compression. The lzf documentation states that on
modern CPUs, compression is as fast as an (unoptimized) memcpy action, making
the compression essentially 'free' when compared to uncompressed data.
lzf can be installed via PECL (see INSTALL).
.. _`The Zend Performance Suite`: http://www.zend.com/horde.php
.. _`Alternative PHP Cache`: http://www.php.net/apc
.. _eAccelerator: http://eaccelerator.net/
.. _XCache: http://xcache.lighttpd.net/
.. _`IBM Article`: http://www.ibm.com/developerworks/web/library/wa-ltwebserv/
.. _`Yahoo's Analysis`: http://yuiblog.com/blog/2006/11/28/performance-research-part-1/
Sending Mail
============
* Generally using a local sendmail command to send mail will result in better
peformance than using a SMTP connection.
* Some MTA servers may be faster or more efficient than others. Consider
switching to a faster format if needed.
IMAP tuning
===========
* Consider an IMAP proxy to allow persistent connections.
imapproxy_ is HIGHLY RECOMMENDED - especially versions 1.2.7rc1 and greater
which contains features used internally by Horde Groupware Webmail Edition to
speed up access to the remote server.
NOTE: if your installation connects to multiple imapproxy instances, you MUST
configure your Horde Groupware Webmail Edition installation to persistently
connect to a single backend over the course of a session. If this is not
possible, you must remove support for imapproxy's advanced features by adding
'XIMAPPROXY' to the 'capability_ignore' parameter in your local
configuration.
* Use an IMAP server that supports CONDSTORE (RFC 4551) and/or QRESYNC (RFC
5162).
These extensions are required to properly cache data and to properly keep the
dynamic display synchronized. It is impossible to do otherwise, and the UI
experience will be limited without these extensions. Additionally, if these
IMAP extensions are available, Horde Groupware Webmail Edition is able to
cache servers which signficantly saves on client/server IMAP interactions.
Technical information can be found here:
http://lists.horde.org/archives/imp/Week-of-Mon-20110523/052285.html
* Some IMAP servers perform better than others. The Horde Project recommends
either Cyrus_ or Dovecot_ as these servers are actively developed, implement
advanced IMAP protocols, and use server-side caching to speed performance.
* Consider switching to a faster mailbox storage format if needed. This may
also require switching the underlying filesystem.
Further information can be found here:
http://wiki2.dovecot.org/MailboxFormat
* Follow the IMAP servers' performance hints:
- Cyrus: http://git.cyrusimap.org/cyrus-imapd/tree/doc/install-perf.html
- Dovecot: http://wiki.dovecot.org/PerformanceTuning
.. _Cyrus: http://www.cyrusimap.org/
.. _Dovecot: http://www.dovecot.org/
.. _imapproxy: http://www.imapproxy.org/
PostgreSQL tuning
=================
* Do a ``VACUUM`` command periodically to tune your database.
* Increase ``shared_buffers`` and ``sort_mem`` memory settings.
* If web server and database is on the same unix host, use unix sockets
instead of network connections for database access.
MySQL tuning
============
* If web server and database is on the same unix host, use unix sockets
instead of network connections for database access.
* Enable mysql query cache if you have sufficient RAM. Edit your ``my.cnf``
file and add the following to the ``[mysqld]`` section (change the memory
size to meet your needs)::
set-variable = query_cache_size=128M
Horde tuning
============
Autoloading
-----------
* Horde Groupware Webmail Edition automatically loads PHP source files on
demand which relies on the PHP autoloading feature introduced with PHP 5 and
the Horde Autoloader library. Both allow to limit the set of source code
files pulled into the system to the minimal amount required to answer the
current request. This saves memory and time but at the same time the
Autoloader library has to map each class name to the path of the
corresponding PHP file that holds the class definition. This procedure is
expensive and can slow the system down. Fortunately the mapping is fixed
unless files are added or removed which usually only happens during an
upgrade.
Thus Autoloading is amenable to caching and an easy way to improve the
performance of the Horde Autoloader library, is to install the Autoloader
Cache extension::
pear install horde/horde_autoloader_cache
This library is not installed by default because it will unconditionally use
any of the following cache backends and does not allow for any further
configuration: `Alternative PHP Cache`_, XCache_, eAccelerator_, or the local
temporary filesystem.
It also doesn't detect the rare case when the file paths of any PHP class in
Horde changes. In this case you either need to use the provided script to
empty the cache::
horde-autoloader-cache-prune
or empty the cache manually, e.g. by restarting the web server or deleting
the cache file from the temporary directory.
VFS
---
* Configure Horde Groupware Webmail Edition to use a VFS filesystem-based
backend. Presently, the SQL VFS backend uses ~5 times the amount of memory as
a filesystem-based backend, so users attaching larger files to outgoing mail
messages may cause PHP out-of-memory errors to occur.
Application tuning
==================
* Some applications contain advanced features that might have a certain impact
on the performance. These features can usually be turned off in the
application's configuration and are explicitly described as being a
performance hit in the configuration web frontend.
Webmail tuning
==============
* Horde Groupware Webmail Edition can use persistent caching on the server side
to store information about user's messages. This results in much reduced
mail server traffic and requires the server to parse the structure of every
message only once. The tradeoff is your cache backend must be able to handle
the potentially large amounts of cached data this option will
produce. However, cache storage is potentially cheap when compared to the
performance gained by using caching.
If CONDSTORE/QRESYNC is available on the server, IMAP flags can be cached.
To use this caching, you must have a ``Cache System`` configured in Horde
Groupware Webmail Edition's ``Administration/Configuration`` screen and have
the relevant settings enabled in the Mail module's configuration screen
(``Administration/Configuration/Mail/Mailbox``).
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