=========================
 Horde Performance Guide
=========================

:Last update:   $Date: 2008/07/16 21:32:10 $
:Revision:      $Revision: 1.9.10.23 $
:Contact:       horde@lists.horde.org

.. contents:: Contents


Some tips on performance tuning systems for Horde.  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**.

* Compile PHP with the ``--enable-inline-optimization`` option to generate the
  fastest possible PHP executable.

* Use of the mcrypt PHP extension should significantly increase performance
  while also increasing security.

* 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 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 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 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.

* 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. Good
  lightweight servers that support SSL include lighttpd_ and Hiawatha_. If
  using a Horde installation that doesn't use SSL (or only uses SSL for
  logins), good choices for servers include thttpd_ or Boa_. 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. Several applications make heavy use of caching and,
  if enabled, you will see a significant increase in performance.

* For applications that support it (this includes IMP as of version 4.2 and
  DIMP), enable 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". NOTE: Horde caching is required to enable
  this feature.

* 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/
.. _`lighttpd`: http://www.lighttpd.net/
.. _`Hiawatha`: http://hiawatha.leisink.org/
.. _`thttpd`: http://www.acme.com/software/thttpd/
.. _`Boa`: http://www.boa.org/
.. _`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 for more persistent connections.  Some IMAP proxies
  are up-imapproxy_ and Perdition_.  To make sense, the proxy
  should be installed on the server running Horde, and this server needs
  enough CPU power to handle the additional load.  If using up-imapproxy,
  make sure SELECT caching is turned off.

* Some IMAP servers (or IMAP mailbox store formats) perform better than
  others.  Consider switching to a faster format if needed.

* Follow the IMAP servers' performance hints:

  - Cyrus: http://asg.web.cmu.edu/cyrus/download/imapd/install-perf.html
  - Dovecot: http://wiki.dovecot.org/PerformanceTuning

.. _up-imapproxy: http://www.imapproxy.org/
.. _Perdition: http://www.vergenet.net/linux/perdition/


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


Application tuning
==================

* Horde 3.2+ and some applications have better performing drivers for Groups,
  Permissions and Shares than the original DataTree drivers. If you upgraded
  from older Horde versions, you can change the driver for those systems to
  "SQL" in the Horde configuration interface. You also have to run the
  according ``convert_datatree_*.php`` scripts in ``horde/scripts/upgrades/``
  and the applications' ``scripts/upgrades/`` directories.

* 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.
