#1 Lighttpd overview
Lighttpd is an open source web server (similar like Apache) to server web pages. It has been developed by a MySQL developer named Jan Kneschke who developed this web server as a part of the C10K problem. Hence immediate reason of birth of Lighttpd is to overcome weakness, like reducing high memory footprint, of Apache web server.
The prefork model that Apache uses consumes a lot of memory (> 20 MB normally) per process. Which means if we multiply number of process to run simultaneously then RAM of server gets exhausted quickly. Lighttpd here beats Apache by using very low memory footprint (just 6MB) which means faster output from web server. The response appears even more faster when static contents are to be delivered. In Netcraft's latest web server survey, we can see Lighttpd among top 5 web servers currently used on Internet.
#2 How to set it up
Normal and most preferred installation instruction can be found from this installation page. For Yum users, a single command yum install zlib pcre lighttpd lighttpd-fastcgi will do almost all things.
If you want to start and stop Lighttpd manually, you're done. To install Lighttpd as a service like Apache, edit and install the init script (only if you have installed Lighttpd from source):
# sed -e 's/FOO/lighttpd/g' doc/rc.lighttpd > lighttpd.init
# chmod a+rx lighttpd.init
# cp lighttpd.init /etc/init.d/lighttpd
# cp -p doc/sysconfig.lighttpd /etc/sysconfig/lighttpd
# install -Dp ./doc/lighttpd.conf /etc/lighttpd/lighttpd.conf
# chkconfig lighttpd on
If you have installed Lighttpd using Yum then just follow last step. You may also use various other commands to start and stop Lighttpd web service like /etc/init.d/lighttpd start|stop|restart|condrestart|reload|status or service lighttpd start|stop|restart|condrestart|reload|status.
To just test lighttpd.conf, run command lighttpd -t -f /PATH/TO/CONF/lighttpd.conf
#3 Differences between Apache and Lighttpd
#3.1 General
The main difference between Apache and Lighttpd is the serving model, Lighttpd is event-driven and Apache is threaded or pre-forked.
Apache provides different multiprocessing models (MPMs) for different runtime environments. The prefork model that Apache uses creates number of processes at startup of service and manages them in a pool. However each process requires lot of memory to handle requests which means the more the processes the more memory will require. That is simultaneous apache processes quickly eat available RAM.
On the other hand Lighttpd uses single process, single thread and non-blocking I/O. For that it uses fastest even handler in the target system like: poll, epoll, kqueue or /dev/poll. This difference makes Lighttpd faster than Apache in serving static files.
However the biggest difference between both is how they support scripting languages (specially like PHP). Apache has upper hand here because it supports easy to use Shared module version, CGI and FastCGI all together while Lighttpd supports only FastCGI at this moment.
#3.2 Configuration level
There is visible difference between styles of configuration files of Lighttpd (lighttpd.conf) and Apache (httpd.conf). Syntax of lighttpd.conf will look more like syntax of php.ini while httpd.conf has XML type syntax. Here is an example of some basic configuration:
#3.2.1 Basic Configuration
#3.2.2 Virtual Hosts
Below is an example of difference between VirtualHosts of Apache and Lighttpd. Example is shown for myproject project.
<VirtualHost *:80>
ServerName 'www.myproject.com'
DocumentRoot '/web/ myproject/web'
ErrorLog '/web/logs/ myproject_error'
</VirtualHost>
#3.2.3 Authentication and Authorization
Lighttpd, at this moment, does not support .htaccess files, so all settings must be specified in the lighttpd.conf file, or the configuration files that it includes. However it understands Apache user files for basic and digest authentication, but group file support is not yet implemented but will be implemented soon. Here is an example of authentication and authorization:
Summarily, configuration file of Lighttpd server behaves like an active script in which you can declare variables, write logic, do computation based upon criteria etc. similar like programming script. This feature makes configuration file alive and agile.
#4 How to run PHP under Lighttpd
#4.1 Configuring PHP under Lighttpd
Apache processes PHP internally i.e using it as Shared module mod_php while Lighttpd runs PHP under FastCGI. Although Apache also supports FastCGI, using PHP under FastCGI with Apache is neglected and is not used. However with Lighttpd, only option is to run under FastCGI, PHP must be compiled with FastCGI option (thought it is not used with Apache). For more information, please read http://trac.lighttpd.net/trac/wiki/TutorialLighttpdAndPHP. Below is the example of difference between running PHP under Apache and lighttpd.
Apache:
LoadModule php5_module modules/libphp5.so
AddType application/x-httpd-php .php
Lighttpd:
server.modules=( ..., "mod_fastcgi", ... )
fastcgi.server=( ".php" =>
(
(
"socket" => "/tmp/php-fastcgi.socket",
"bin-path" => "/usr/bin/php-cgi",
"broken-scriptfilename" => "enable",
"bin-environment" =>
(
"PHP_FCGI_CHILDREN" => "2",
"PHP_FCGI_MAX_REQUESTS" => "5000"
),
"min-procs" => 1,
"max-procs" => 2,
"idle-timeout" => 60
)
)
)
You may require to set path of php-cgi according to your setup. Please note that directive server.modules actually exists along with other modules on top of configuration file hence above line indicates that mod_fastcgi should be enabled in lighttpd.cnf.
Then it will require to set 1 directive in following way in php.ini configuration file if it exists, if doesn't then nothing to do.
cgi.fix_pathinfo=1
Last 4 directives of above mentioned configuration are for running PHP scripts in better ways.
#4.2 Application wise changes
As FastCGI is a separate process, we can't handle directives of PHP into configuration file of web server (i.e lighttpd.conf). This is one of the biggest drawback of FastCGI that is why PHP is not used under FastCGI. Moreover under FastCGI mode, your PHP script would get limited support from web server which may force you to change or rewrite your scripts. Hence it is not recommended to use PHP under Lighttpd (at this moment because Lighttpd currently supports only FastCGI mode) because of it's lack of features that PHP will require like enabling configuration options of php.ini in configuration file for all hosts or per host base.
Moreover many benchmarks shows that PHP runs slower under FastCGI than under shared version on Apache.
However if it is required to run PHP on Lighttpd, then 2 major changes will require. They are:
#5 mod_uploadprogress and Prototype
This feature will be available in Lighttpd version 1.5.0 which is not released yet, hence can not test or write more about it. More information about this module can be found at here. However when it will get released, it would surely be one of the finest module of Lighttpd server because it can be easily integrated with front-end applications using JSON.
#6 Lighttpd and output compression
Lighttpd provides output compression for static data through mod_compress module. Which means before sending static contents to client, mod_compress compresses it and saves at specified path. This compressed and cached copy will be served directly from cached location when similar request is made from same or different client. Thus saving valuable bandwidth and increasing response time.
Lighttpd supports 3 types of compressions viz. deflate, gzip and bzip2. The limitation of compressing and caching is that Lighttpd can not compress files with size more than 128 MByte and less than 128 Bytes.
To enable compression we need to set 3 directives in lighttpd.conf file. They are:
compress.cache-dir="/var/www/cache/myproject/"
compress.filetype=("text/plain", "text/html")
compress.max-filesize=1 MB
However since there is upper limit of file size of 128 Mbytes, the last directive is not necessary to declare. While compressing various types of static data, it should be kept in mind that if no file type or wrong file type is mentioned then no file will get compressed.
You may require to manually create cache folder and assign necessary write permissions to it. These cached contents do not automatically get cleared hence it is left to developer to clean it at periodic level when required. Following type of command can be used to remove contents that are older than a week.
$ find /var/www/cache/myproject/ -type f -mtime +7 | xargs -r rm
To compress dynamic contents, we need to reply on PHP itself as PHP natively supports good compression of dynamic contents. For that following 2 directives are to be set in php.ini or in equivalent configuration file.
zlib.output_compression=1
zlib.output_handler=On
Please note that to use zlib.output_compression, value of output_handler should be zlib.output_handler instead of standard output_handler. To do so, output_handler directive is to be set in following way:
output_handler=zlib.output_handler
or
zlib.output_handler=On
#7 Lighttpd and caching
#7.1 Caching overview
Caching is also another method to gain better performance in serving contents and increasing response time of your PHP scripts. There are several types of caching softwares available for PHP. Some important from them are Zend Platform, APC (APC GUI), XCache, eAccelerator, ionCube Encoder and PHP Accelerator. Certain web servers like Lighttpd provides built in modules for caching static contents at web server level. They are mod_expire, mod_mem_cache and mod_cml. Hence using combination of caching static and dynamic contents effectively, we can gain lot of speed in serving contents. However all of these mechanisms are not similar.
Aforementioned independent softwares are for Opcode/Bytecode caching i.e caching your PHP script into compiled state so that when new request arrives for same script, cache software will server compiled version of code directly from cache rather than reading file again from the disk and then compiling. From these 6, eAccelerator, XCache and APC are widely used caching softwares. This benchmarks also show that how XCache and APC are better than others. We will learn more about XCache in a short while.
As said earlier that only good combination of static and dynamic contents can give considerable boost in performance, we should try to cache as much contents as possible. To cache static contents, integrated modules of web server are the best candidates. In case of Lighttpd they are mod_expire and mod_mem_cache (however this is not provided as default).
#7.2 mod_expire
Mod_expire controls the Expire header in the Response Header of HTTP/1.0 messages. It is useful to set it for static files which should be cached like images, style-sheets etc. To use this module, first it needs to get enabled in server.modules directive array. Then module specific directives are to be set in server's configuration file as shown below.
<access|modification> <number> <years|months|days|hours|minutes|seconds>
Some examples could be like:
expire.url = ( "" => "access 2 hours" )
}
Values can be hours, months, days etc. depending upon requirement.
#7.3 mod_mem_cache
#7.5.1 Installing XCache
The standard way to install XCache is from source. Get your desired version of XCache from here. Then follow below steps to install it.
# tar -zxf xcache-*.tar.gz
# cd xcache
# phpize
# ./configure --enable-xcache
# make
# su
# make install
# cat xcache.ini >> /etc/php.ini
To make sure XCache is properly installed, run below command.
$ php-fcgi -v
It will show string like with XCache vX.X, Copyright (c) XXXX-XXXX, by XXX. Same can be checked from output of phpinfo() function also. Once XCache is installed, it will require to edit xcache.ini which contain various caching related directives to be used. However it is not mandatory to edit or change. A complete explanation of all the directives can be found from http://trac.lighttpd.net/xcache/wiki/PhpIni.
#7.5.2 Configuring Administrator panel
XCache Administrator panel is an important web interface that you can monitor and operate your opcode cache, seeing how well(or bad) it goes. Since this page is protected by http-auth, it will require to provide certain values in xcache.ini. For that set below 2 directives.
xcache.admin.user='USER'
xcache.admin.pass='MD5(PASSWORD)'
where USER is name of user you wish to use and MD5(PASSWORD) is MD5 encrypted string of password that you wish to use for given USER.
To set up web interface, copy xcache/admin/ (the whole directory) to your web document-root or sub-directory of it then request it from your browser, a http-auth prompt will popup where you will require to provide above USER and PASSWORD (as a normal string, not MD5 encrypted string). However sometimes installing XCache from rpm based utilities it may require to alias in web server instead of copying the script. To do so, add below directive in your server configuration file.
Apache:
Alias /xcache-admin/ /usr/share/xcache/admin/
Lighttpd:
alias.url += ("/xcache-admin/" => "/usr/share/xcache/admin/")
Gaining performance boost by using caching mechanism is tricky. Unless used carefully, it cannot give required boost. As we know that we can't cache everything (specially dynamic contents), we should try to cache whatever is left. This can be achieved by various types of caching as discussed above. Static contents are well cached by clients, if not then can be cached by web servers. PHP scripts can be cached using Opcode caching softwares like APC, XCache etc. While static part of dynamic data can be cached by modules like mod_cml (for lighttpd web server only).
#8 Summary
Summarily, Lighttpd web server is surely worth to have look at it and to be used for serving static data. For dynamic contents like PHP scripts, it is not optimized (because of support of only FastCGI) hence we have to wait until Shared module version PHP get started to support by it. At this moment it is widely used to server static contents only. So it will take time for it to really start competing with Apache.
However certain modules like mod_secdownload, mod_compress, mod_geoip, mod_trigger_b4_dl, mod_uploadprogress, mod_useronline etc. are peculiar modules of Lighttpd which can make it stand firmly with currently popular web servers.
#9 Links
http://www.onlamp.com/pub/a/onlamp/2007/04/05/the-lighttpd-web-server.html
http://survey.netcraft.com/Reports/0703/
http://schlitt.info/applications/blog/index.php?/archives/504-Apache-vs.-Lighttpd-echo-performance.html
http://trac.lighttpd.net/trac/wiki/TutorialInstallation
http://trac.lighttpd.net/trac/wiki/TutorialConfiguration
http://trac.lighttpd.net/trac/wiki/Docs:ConfigurationOptions
http://trac.lighttpd.net/trac/wiki/TutorialLighttpdAndPHP
http://trac.lighttpd.net/trac/wiki/Docs:ModUploadProgress
http://trac.lighttpd.net/trac/wiki/Docs:ModCompress
http://blog.lighttpd.net/articles/2006/08/01/mod_uploadprogress-is-back
http://trac.lighttpd.net/trac/wiki/Docs:ModCML
http://www-128.ibm.com/developerworks/library/os-php-fastapps1/index.html
http://trac.lighttpd.net/xcache/wiki/Faq
Lighttpd is an open source web server (similar like Apache) to server web pages. It has been developed by a MySQL developer named Jan Kneschke who developed this web server as a part of the C10K problem. Hence immediate reason of birth of Lighttpd is to overcome weakness, like reducing high memory footprint, of Apache web server.
The prefork model that Apache uses consumes a lot of memory (> 20 MB normally) per process. Which means if we multiply number of process to run simultaneously then RAM of server gets exhausted quickly. Lighttpd here beats Apache by using very low memory footprint (just 6MB) which means faster output from web server. The response appears even more faster when static contents are to be delivered. In Netcraft's latest web server survey, we can see Lighttpd among top 5 web servers currently used on Internet.
#2 How to set it up
Normal and most preferred installation instruction can be found from this installation page. For Yum users, a single command yum install zlib pcre lighttpd lighttpd-fastcgi will do almost all things.
If you want to start and stop Lighttpd manually, you're done. To install Lighttpd as a service like Apache, edit and install the init script (only if you have installed Lighttpd from source):
# sed -e 's/FOO/lighttpd/g' doc/rc.lighttpd > lighttpd.init
# chmod a+rx lighttpd.init
# cp lighttpd.init /etc/init.d/lighttpd
# cp -p doc/sysconfig.lighttpd /etc/sysconfig/lighttpd
# install -Dp ./doc/lighttpd.conf /etc/lighttpd/lighttpd.conf
# chkconfig lighttpd on
If you have installed Lighttpd using Yum then just follow last step. You may also use various other commands to start and stop Lighttpd web service like /etc/init.d/lighttpd start|stop|restart|condrestart|reload|status or service lighttpd start|stop|restart|condrestart|reload|status.
To just test lighttpd.conf, run command lighttpd -t -f /PATH/TO/CONF/lighttpd.conf
#3 Differences between Apache and Lighttpd
#3.1 General
The main difference between Apache and Lighttpd is the serving model, Lighttpd is event-driven and Apache is threaded or pre-forked.
Apache provides different multiprocessing models (MPMs) for different runtime environments. The prefork model that Apache uses creates number of processes at startup of service and manages them in a pool. However each process requires lot of memory to handle requests which means the more the processes the more memory will require. That is simultaneous apache processes quickly eat available RAM.
On the other hand Lighttpd uses single process, single thread and non-blocking I/O. For that it uses fastest even handler in the target system like: poll, epoll, kqueue or /dev/poll. This difference makes Lighttpd faster than Apache in serving static files.
However the biggest difference between both is how they support scripting languages (specially like PHP). Apache has upper hand here because it supports easy to use Shared module version, CGI and FastCGI all together while Lighttpd supports only FastCGI at this moment.
#3.2 Configuration level
There is visible difference between styles of configuration files of Lighttpd (lighttpd.conf) and Apache (httpd.conf). Syntax of lighttpd.conf will look more like syntax of php.ini while httpd.conf has XML type syntax. Here is an example of some basic configuration:
#3.2.1 Basic Configuration
Apache:
DocumentRoot /var/www/html
CustomLog /var/www/logs/access
ErrorLog /var/www/logs/error
User apache
Group apache
Lighttpd:
server.document-root="/var/www/html"
accesslog.filename="/var/www/logs/access"
server.errorlog="/var/www/logs/error"
server.username="apache"
server.groupname="apache"
server.modules=("mod_cml")
#3.2.2 Virtual Hosts
Below is an example of difference between VirtualHosts of Apache and Lighttpd. Example is shown for myproject project.
Apache:
NameVirtualHost *
ServerName 'www.myproject.com'
DocumentRoot '/web/
ErrorLog '/web/logs/
</VirtualHost>
Include conf.d/virtualhosts/*.conf
Lighttpd:
$HTTP[“host”] == “www.myproject.com” {
server.document-root=”/web/myproject/web”
server.errorlog="/web/myproject_error"
}
#3.2.3 Authentication and Authorization
Lighttpd, at this moment, does not support .htaccess files, so all settings must be specified in the lighttpd.conf file, or the configuration files that it includes. However it understands Apache user files for basic and digest authentication, but group file support is not yet implemented but will be implemented soon. Here is an example of authentication and authorization:
Apache:
<Directory ~>
AuthName "Authentication required to access this area."
AuthType Basic
AuthUserFile /web/myproject/docs/valid.users
Order deny,allow
Require valid-user
</Directory>
AuthName "Authentication required to access this area."
AuthType Basic
AuthUserFile /web/myproject/docs/valid.users
Order deny,allow
Require valid-user
</Directory>
Lighttpd:
auth.backend="htpasswd"
auth.backend.htpasswd.userfile="/web/myproject/docs/valid.users"
auth.require=
("~" =>
(
"method" =>"basic",
"realm" =>"Authentication required to access this area.",
"require"=>"valid-user"
)
)
Summarily, configuration file of Lighttpd server behaves like an active script in which you can declare variables, write logic, do computation based upon criteria etc. similar like programming script. This feature makes configuration file alive and agile.
#4 How to run PHP under Lighttpd
#4.1 Configuring PHP under Lighttpd
Apache processes PHP internally i.e using it as Shared module mod_php while Lighttpd runs PHP under FastCGI. Although Apache also supports FastCGI, using PHP under FastCGI with Apache is neglected and is not used. However with Lighttpd, only option is to run under FastCGI, PHP must be compiled with FastCGI option (thought it is not used with Apache). For more information, please read http://trac.lighttpd.net/trac/wiki/TutorialLighttpdAndPHP. Below is the example of difference between running PHP under Apache and lighttpd.
Apache:
LoadModule php5_module modules/libphp5.so
AddType application/x-httpd-php .php
Lighttpd:
server.modules=( ..., "mod_fastcgi", ... )
fastcgi.server=( ".php" =>
(
(
"socket" => "/tmp/php-fastcgi.socket",
"bin-path" => "/usr/bin/php-cgi",
"broken-scriptfilename" => "enable",
"bin-environment" =>
(
"PHP_FCGI_CHILDREN" => "2",
"PHP_FCGI_MAX_REQUESTS" => "5000"
),
"min-procs" => 1,
"max-procs" => 2,
"idle-timeout" => 60
)
)
)
You may require to set path of php-cgi according to your setup. Please note that directive server.modules actually exists along with other modules on top of configuration file hence above line indicates that mod_fastcgi should be enabled in lighttpd.cnf.
Then it will require to set 1 directive in following way in php.ini configuration file if it exists, if doesn't then nothing to do.
cgi.fix_pathinfo=1
Last 4 directives of above mentioned configuration are for running PHP scripts in better ways.
#4.2 Application wise changes
As FastCGI is a separate process, we can't handle directives of PHP into configuration file of web server (i.e lighttpd.conf). This is one of the biggest drawback of FastCGI that is why PHP is not used under FastCGI. Moreover under FastCGI mode, your PHP script would get limited support from web server which may force you to change or rewrite your scripts. Hence it is not recommended to use PHP under Lighttpd (at this moment because Lighttpd currently supports only FastCGI mode) because of it's lack of features that PHP will require like enabling configuration options of php.ini in configuration file for all hosts or per host base.
Moreover many benchmarks shows that PHP runs slower under FastCGI than under shared version on Apache.
However if it is required to run PHP on Lighttpd, then 2 major changes will require. They are:
- To move all PHP related setting either in php.ini directly or in configuration or global file of the application.
- Removing all Apache web server related variables and settings from application.
#5 mod_uploadprogress and Prototype
This feature will be available in Lighttpd version 1.5.0 which is not released yet, hence can not test or write more about it. More information about this module can be found at here. However when it will get released, it would surely be one of the finest module of Lighttpd server because it can be easily integrated with front-end applications using JSON.
#6 Lighttpd and output compression
Lighttpd provides output compression for static data through mod_compress module. Which means before sending static contents to client, mod_compress compresses it and saves at specified path. This compressed and cached copy will be served directly from cached location when similar request is made from same or different client. Thus saving valuable bandwidth and increasing response time.
Lighttpd supports 3 types of compressions viz. deflate, gzip and bzip2. The limitation of compressing and caching is that Lighttpd can not compress files with size more than 128 MByte and less than 128 Bytes.
To enable compression we need to set 3 directives in lighttpd.conf file. They are:
compress.cache-dir="/var/www/cache/myproject/"
compress.filetype=("text/plain", "text/html")
compress.max-filesize=1 MB
However since there is upper limit of file size of 128 Mbytes, the last directive is not necessary to declare. While compressing various types of static data, it should be kept in mind that if no file type or wrong file type is mentioned then no file will get compressed.
You may require to manually create cache folder and assign necessary write permissions to it. These cached contents do not automatically get cleared hence it is left to developer to clean it at periodic level when required. Following type of command can be used to remove contents that are older than a week.
$ find /var/www/cache/myproject/ -type f -mtime +7 | xargs -r rm
To compress dynamic contents, we need to reply on PHP itself as PHP natively supports good compression of dynamic contents. For that following 2 directives are to be set in php.ini or in equivalent configuration file.
zlib.output_compression=1
zlib.output_handler=On
Please note that to use zlib.output_compression, value of output_handler should be zlib.output_handler instead of standard output_handler. To do so, output_handler directive is to be set in following way:
output_handler=zlib.output_handler
or
zlib.output_handler=On
#7 Lighttpd and caching
#7.1 Caching overview
Caching is also another method to gain better performance in serving contents and increasing response time of your PHP scripts. There are several types of caching softwares available for PHP. Some important from them are Zend Platform, APC (APC GUI), XCache, eAccelerator, ionCube Encoder and PHP Accelerator. Certain web servers like Lighttpd provides built in modules for caching static contents at web server level. They are mod_expire, mod_mem_cache and mod_cml. Hence using combination of caching static and dynamic contents effectively, we can gain lot of speed in serving contents. However all of these mechanisms are not similar.
Aforementioned independent softwares are for Opcode/Bytecode caching i.e caching your PHP script into compiled state so that when new request arrives for same script, cache software will server compiled version of code directly from cache rather than reading file again from the disk and then compiling. From these 6, eAccelerator, XCache and APC are widely used caching softwares. This benchmarks also show that how XCache and APC are better than others. We will learn more about XCache in a short while.
As said earlier that only good combination of static and dynamic contents can give considerable boost in performance, we should try to cache as much contents as possible. To cache static contents, integrated modules of web server are the best candidates. In case of Lighttpd they are mod_expire and mod_mem_cache (however this is not provided as default).
#7.2 mod_expire
Mod_expire controls the Expire header in the Response Header of HTTP/1.0 messages. It is useful to set it for static files which should be cached like images, style-sheets etc. To use this module, first it needs to get enabled in server.modules directive array. Then module specific directives are to be set in server's configuration file as shown below.
<access|modification> <number> <years|months|days|hours|minutes|seconds>
Some examples could be like:
- Cache contents of folder images for 2 hours.
- Cache contents of all sub-folders of images folder for 2 hours.
expire.url = ( "" => "access 2 hours" )
}
Values can be hours, months, days etc. depending upon requirement.
#7.3 mod_mem_cache
Mod_mem_cache is a plugin which stores content of files in memory for faster serving. That is it stores specified file types into memory to serve directly from there without going to read it from disk from specified location thus saving disk read access time. This module is a 3rd party module, hence is not included in the official distribution of Lighttpd.
This module doesn't seem that much promising to use effectively for caching as memory should be used for processing data rather than storing data. Moreover memory should not be occupied for serving files that can reside and easily managed on disks. For example when we have thousands of images to be served then it is not advisable to store them into memory just to serve it faster. More information about this plugin can be found at here.
#7.4 mod_cml (Cache Meta Language)
Mod_cml is an another caching module similar like mod_expire which is provided by Lighttpd to cache static contents of dynamic pages. The difference between mod_expire and mod_cml is that mod_cml can cache fragmented static contents which are part of dynamic contents. For example a dynamic page called index.php might have static contents like menu.html, banner.html inside it which are not integral part of index.php. In such case using mod_cml, these 2 static contents can be cached and can be delivered directly from there.
But such type of caching can not be handled directly by Lighttpd web server and mod_cml hence we need to write some code in PHP or in special CML scripts for mod_cml which is written in lua programming language.
To use mod_cml, it requires to install lua programming language and libmemcache-1.3.x. Additionally Lighttpd must be compiled with 2 options --with-lua and –with-memcache.
#7.5 XCache
XCache is a newly emerging candidate in the market of caching PHP scripts. This is an independent software and not a module of Lighttpd. However it has been written by developers of Lighttpd.
XCache is an open-source opcode cacher, which means that it accelerates the performance of PHP on servers. It optimizes performance by removing the compilation time of PHP scripts by caching the compiled state of PHP scripts into the shm (RAM) and uses the compiled version straight from the RAM. This will increase the rate of page generation time by up to 5 times as it also optimizes many other aspects of php scripts and reduce server load. Some of the good features of XCache are:
This module doesn't seem that much promising to use effectively for caching as memory should be used for processing data rather than storing data. Moreover memory should not be occupied for serving files that can reside and easily managed on disks. For example when we have thousands of images to be served then it is not advisable to store them into memory just to serve it faster. More information about this plugin can be found at here.
#7.4 mod_cml (Cache Meta Language)
Mod_cml is an another caching module similar like mod_expire which is provided by Lighttpd to cache static contents of dynamic pages. The difference between mod_expire and mod_cml is that mod_cml can cache fragmented static contents which are part of dynamic contents. For example a dynamic page called index.php might have static contents like menu.html, banner.html inside it which are not integral part of index.php. In such case using mod_cml, these 2 static contents can be cached and can be delivered directly from there.
But such type of caching can not be handled directly by Lighttpd web server and mod_cml hence we need to write some code in PHP or in special CML scripts for mod_cml which is written in lua programming language.
To use mod_cml, it requires to install lua programming language and libmemcache-1.3.x. Additionally Lighttpd must be compiled with 2 options --with-lua and –with-memcache.
#7.5 XCache
XCache is a newly emerging candidate in the market of caching PHP scripts. This is an independent software and not a module of Lighttpd. However it has been written by developers of Lighttpd.
XCache is an open-source opcode cacher, which means that it accelerates the performance of PHP on servers. It optimizes performance by removing the compilation time of PHP scripts by caching the compiled state of PHP scripts into the shm (RAM) and uses the compiled version straight from the RAM. This will increase the rate of page generation time by up to 5 times as it also optimizes many other aspects of php scripts and reduce server load. Some of the good features of XCache are:
- Optimized opcode cache.
- Using a generator to produce C code, reduces human mistake greatly.
- Running stable on PHP_4_3/PHP_4_4
- Supported and tested on all latest php cvs branches, such as PHP_4_3 PHP_4_4 PHP_5_0 PHP_5_1 PHP_5_2 HEAD (6.x)
- Alpha supported for in-alpha-php6, with Unicode enabled.
- Read-only Cacher Protection that prevents the cache from being corrupted by php-core/extension or any code other than XCache itself.
- Atomic get/set/inc/dec API operation on var cache for php programmers.
- Optimizer
- Encoder/Decoder(Loader)
- Administrator Script
The last feature allows administrator to view statistic and cached PHP variables and manage caching behavior of XCache.
- view statistics
- to see if it's AutoDisableOnCorrupted?
- view cached php/variable list
- clear cache
#7.5.1 Installing XCache
The standard way to install XCache is from source. Get your desired version of XCache from here. Then follow below steps to install it.
# tar -zxf xcache-*.tar.gz
# cd xcache
# phpize
# ./configure --enable-xcache
# make
# su
# make install
# cat xcache.ini >> /etc/php.ini
To make sure XCache is properly installed, run below command.
$ php-fcgi -v
It will show string like with XCache vX.X, Copyright (c) XXXX-XXXX, by XXX. Same can be checked from output of phpinfo() function also. Once XCache is installed, it will require to edit xcache.ini which contain various caching related directives to be used. However it is not mandatory to edit or change. A complete explanation of all the directives can be found from http://trac.lighttpd.net/xcache/wiki/PhpIni.
#7.5.2 Configuring Administrator panel
XCache Administrator panel is an important web interface that you can monitor and operate your opcode cache, seeing how well(or bad) it goes. Since this page is protected by http-auth, it will require to provide certain values in xcache.ini. For that set below 2 directives.
xcache.admin.user='USER'
xcache.admin.pass='MD5(PASSWORD)'
where USER is name of user you wish to use and MD5(PASSWORD) is MD5 encrypted string of password that you wish to use for given USER.
To set up web interface, copy xcache/admin/ (the whole directory) to your web document-root or sub-directory of it then request it from your browser, a http-auth prompt will popup where you will require to provide above USER and PASSWORD (as a normal string, not MD5 encrypted string). However sometimes installing XCache from rpm based utilities it may require to alias in web server instead of copying the script. To do so, add below directive in your server configuration file.
Apache:
Alias /xcache-admin/ /usr/share/xcache/admin/
Lighttpd:
alias.url += ("/xcache-admin/" => "/usr/share/xcache/admin/")
Gaining performance boost by using caching mechanism is tricky. Unless used carefully, it cannot give required boost. As we know that we can't cache everything (specially dynamic contents), we should try to cache whatever is left. This can be achieved by various types of caching as discussed above. Static contents are well cached by clients, if not then can be cached by web servers. PHP scripts can be cached using Opcode caching softwares like APC, XCache etc. While static part of dynamic data can be cached by modules like mod_cml (for lighttpd web server only).
#8 Summary
Summarily, Lighttpd web server is surely worth to have look at it and to be used for serving static data. For dynamic contents like PHP scripts, it is not optimized (because of support of only FastCGI) hence we have to wait until Shared module version PHP get started to support by it. At this moment it is widely used to server static contents only. So it will take time for it to really start competing with Apache.
However certain modules like mod_secdownload, mod_compress, mod_geoip, mod_trigger_b4_dl, mod_uploadprogress, mod_useronline etc. are peculiar modules of Lighttpd which can make it stand firmly with currently popular web servers.
#9 Links
http://www.onlamp.com/pub/a/onlamp/2007/04/05/the-lighttpd-web-server.html
http://survey.netcraft.com/Reports/0703/
http://schlitt.info/applications/blog/index.php?/archives/504-Apache-vs.-Lighttpd-echo-performance.html
http://trac.lighttpd.net/trac/wiki/TutorialInstallation
http://trac.lighttpd.net/trac/wiki/TutorialConfiguration
http://trac.lighttpd.net/trac/wiki/Docs:ConfigurationOptions
http://trac.lighttpd.net/trac/wiki/TutorialLighttpdAndPHP
http://trac.lighttpd.net/trac/wiki/Docs:ModUploadProgress
http://trac.lighttpd.net/trac/wiki/Docs:ModCompress
http://blog.lighttpd.net/articles/2006/08/01/mod_uploadprogress-is-back
http://trac.lighttpd.net/trac/wiki/Docs:ModCML
http://www-128.ibm.com/developerworks/library/os-php-fastapps1/index.html
http://trac.lighttpd.net/xcache/wiki/Faq
