115 lines
4.2 KiB
Plaintext
115 lines
4.2 KiB
Plaintext
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README.SuSE for Apache 2
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For The Impatient
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=================
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o There are several MPM packages (MPM = multiprocessing module, which implements
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the threads/processes model). The MPM packages contain the actual apache binary.
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At least one MPM package must be installed.
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o The apache v1 and v2 packages can be installed and run side by side :)
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o Some commands have a "2" suffix, and are thus easily confused with Apache 1
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commands -- if you have an old apache (1.3) installation around.
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o Edit /etc/sysconfig/apache2 to configure the list of modules to load, and other things.
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It is no longer required to run SuSEconfig after such changes. (In fact, the
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SuSEconfig.apache2 does no longer exist.)
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o For building apache modules, there are 4 apxs commands (all come with the
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apache2-devel package):
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apxs2 builds a common module for all MPMs and installs to /usr/lib/apache2
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apxs2-prefork builds for prefork and installs to /usr/lib/apache2-prefork
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apxs2-worker builds for worker and installs to /usr/lib/apache2-worker
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If you build apache modules, the configure script might not find apxs, and
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you'll need an option like --with-apxs=apxs2[-worker, ...], or of course you can set
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a symlink to apxs2.
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o The Apache Runtime (APR) is in the "libapr0" package (this package was named "apr"
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in the past (8.1))
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Choosing the right MPM for your application
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===========================================
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apache2-prefork is implemented with a prefork regime, while
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apache2-worker uses a hybrid threaded/preforked model.
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Which one to use? The short answer is:
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- if in doubt, simply use prefork
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- use prefork if you use mod_php4
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- use worker if you need maximal performance with (possibly) less resources
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(smaller memory footprint of threade compared to the same number as processes)
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The following nice article has a more in depth answer:
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http://www.onlamp.com/pub/a/apache/2004/06/17/apacheckbk.html
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See
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http://httpd.apache.org/docs-2.2/mpm.html and
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http://httpd.apache.org/docs-2.2/misc/perf-tuning.html#compiletime
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for more technical details.
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In general, using a threaded MPM (worker) requires that all libraries that are
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loaded into apache (and libraries loaded by them in turn) be threadsafe as well.
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See
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http://httpd.apache.org/docs-2.2/developer/thread_safety.html for a status on
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some libraries.
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Upgrading from apache 1.3
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=========================
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For a smooth transition from apache 1.3, apache 2 is installable alongside apache
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1.3. There are a few modules for apache 1 that have not been ported or enough
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tested for apache 2, but most important modules are available by now.
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The mechanism of specifying modules to load into the server has been cleaned up
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so a reasonable default set of modules is loaded. (It is not useful to load all
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available modules by default, it would make the server quite big and slow. This
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is important given as the number of modules in the apache base distribution is
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rising and rising (about 50 at this time).
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In previous apache packages (1.3), modules were activated by setting a
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APACHE_MOD_XYZ variable to "yes" and running SuSEconfig.
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Nowadays, modules are activated by adding them to a the APACHE_MODULES
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variable in /etc/sysconfig/apache2, and simply restarting apache.
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Building modules for apache 2
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=============================
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Therefore, the different MPMs will be needed and a mechanism to build
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the modules spesific to them. This can now be done with the apxs2,
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apxs2-worker or apxs2-prefork script.
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For a module's configure script, you would typically use
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--which-apxs=/usr/sbin/apxs2-prefork
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In RPM spec files, you can use
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%define apxs apxs2
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%define apache_libexecdir %(%{apxs} -q libexecdir)
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to build modules, or use apxs2-prefork (for instance) to build a module
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specifically for the prefork MPM.
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To further the example, apxs2-prefork will install a module below
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/usr/lib/apache2-prefork/, while "apxs2" will install it below
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/usr/lib/apache2/.
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-a adds the module to APACHE_MODULES in /etc/sysconfig/apache2, which in turn
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takes care of loading the module.
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Thus, usually you will only have to call
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apxs2 -cia my_module.c
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and all is fine.
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--
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Suggestions or bug reports (via http://bugzilla.novell.com/) are most
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welcome.
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Mar 14 2005, Peter Poeml
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