===================================================
 Horde Groupware Webmail Edition Performance Guide
===================================================

:Last update:   $Date: 2008/05/25 18:43:36 $
:Revision:      $Revision: 1.2 $
: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**.

* 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 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.

* Enable Apache keepalives.

* You can configure Horde Groupware Webmail Edition 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 Groupware Webmail Edition 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 Groupware. 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.

.. _`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 Groupware Webmail Edition, 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
==================

* 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 IMAP 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.

  To use this caching, you must have a ``Cache System`` configured in Horde's
  ``Administration/Setup`` screen and have the relevant settings enabled in
  IMP's setup screen (``Administration/Setup/Webmail/Mailbox and Fetchmail``.
