RELOAD(1)						User Contributed Perl Documentation						 RELOAD(1)

NAME

       Apache::Reload - Reload Perl Modules when Changed on Disk

Synopsis
	 # Monitor and reload all modules in %INC:
	 # httpd.conf:
	 PerlModule Apache::Reload
	 PerlInitHandler Apache::Reload

	 # Reload groups of modules:
	 # httpd.conf:
	 PerlModule Apache::Reload
	 PerlInitHandler Apache::Reload
	 PerlSetVar ReloadAll Off
	 PerlSetVar ReloadModules "ModPerl::* Apache::*"
	 #PerlSetVar ReloadDebug On

	 # Reload a single module from within itself:
	 package My::Apache::Module;
	 use Apache::Reload;
	 sub handler { ... }
	 1;

Description
       "Apache::Reload" reloads modules that change on the disk.

       When Perl pulls a file via "require", it stores the filename in the global hash %INC.  The next time Perl tries to "require" the same file,
       it sees the file in %INC and does not reload from disk.	This module's handler can be configured to iterate over the modules in %INC and
       reload those that have changed on disk or only specific modules that have registered themselves with "Apache::Reload". It can also do the
       check for modified modules, when a special touch-file has been modified.

       Note that "Apache::Reload" operates on the current context of @INC.  Which means, when called as a "Perl*Handler" it will not see @INC
       paths added or removed by "Apache::Registry" scripts, as the value of @INC is saved on server startup and restored to that value after each
       request.  In other words, if you want "Apache::Reload" to work with modules that live in custom @INC paths, you should modify @INC when the
       server is started.  Besides, 'use lib' in the startup script, you can also set the "PERL5LIB" variable in the httpd's environment to
       include any non-standard 'lib' directories that you choose.  For example, to accomplish that you can include a line:

	 PERL5LIB=/home/httpd/perl/extra; export PERL5LIB

       in the script that starts Apache. Alternatively, you can set this environment variable in httpd.conf:

	 PerlSetEnv PERL5LIB /home/httpd/perl/extra

       Monitor All Modules in %INC

       To monitor and reload all modules in %INC, simply add the following configuration to your httpd.conf:

	 PerlModule Apache::Reload
	 PerlInitHandler Apache::Reload

       Register Modules Implicitly

       To only reload modules that have registered with "Apache::Reload", add the following to the httpd.conf:

	 PerlModule Apache::Reload
	 PerlInitHandler Apache::Reload
	 PerlSetVar ReloadAll Off
	 # ReloadAll defaults to On

       Then any modules with the line:

	 use Apache::Reload;

       Will be reloaded when they change.

       Register Modules Explicitly

       You can also register modules explicitly in your httpd.conf file that you want to be reloaded on change:

	 PerlModule Apache::Reload
	 PerlInitHandler Apache::Reload
	 PerlSetVar ReloadAll Off
	 PerlSetVar ReloadModules "My::Foo My::Bar Foo::Bar::Test"

       Note that these are split on whitespace, but the module list must be in quotes, otherwise Apache tries to parse the parameter list.

       The "*" wild character can be used to register groups of files under the same namespace. For example the setting:

	 PerlSetVar ReloadModules "ModPerl::* Apache::*"

       will monitor all modules under the namespaces "ModPerl::" and "Apache::".

       Special "Touch" File

       You can also declare a file, which when gets touch(1)ed, causes the reloads to be performed. For example if you set:

	 PerlSetVar ReloadTouchFile /tmp/reload_modules

       and don't touch(1) the file /tmp/reload_modules, the reloads won't happen until you go to the command line and type:

	 % touch /tmp/reload_modules

       When you do that, the modules that have been changed, will be magically reloaded on the next request. This option works with any mode
       described before.

Performance Issues
       This modules is perfectly suited for a development environment. Though it's possible that you would like to use it in a production environ-
       ment, since with "Apache::Reload" you don't have to restart the server in order to reload changed modules during software updates. Though
       this convenience comes at a price:

       o   If the "touch" file feature is used, "Apache::Reload" has to stat(2) the touch file on each request, which adds a slight but most
	   likely insignificant overhead to response times. Otherwise "Apache::Reload" will stat(2) each registered module or even worse--all mod-
	   ules in %INC, which will significantly slow everything down.

       o   Once the child process reloads the modules, the memory used by these modules is not shared with the parent process anymore. Therefore
	   the memory consumption may grow significantly.

       Therefore doing a full server stop and restart is probably a better solution.

Debug
       If you aren't sure whether the modules that are supposed to be reloaded, are actually getting reloaded, turn the debug mode on:

	 PerlSetVar ReloadDebug On

Threaded MPM and Multiple Perl Interpreters
       If you use "Apache::Reload" with a threaded MPM and multiple Perl interpreters, the modules will be reloaded by each interpreter as they
       are used, not every interpreters at once.  Similar to mod_perl 1.x where each child has its own Perl interpreter, the modules are reloaded
       as each child is hit with a request.

       If a module is loaded at startup, the syntax tree of each subroutine is shared between interpreters (big win), but each subroutine has its
       own padlist (where lexical my variables are stored).  Once "Apache::Reload" reloads a module, this sharing goes away and each Perl inter-
       preter will have its own copy of the syntax tree for the reloaded subroutines.

Pseudo-hashes
       The short summary of this is: Don't use pseudo-hashes. They are deprecated since Perl 5.8 and will be removed in 5.10

       Use an array with constant indexes. Its faster in the general case, its more guaranteed, and generally, it works.

       The long summary is that some work has been done to get this module working with modules that use pseudo-hashes, but it's still broken in
       the case of a single module that contains multiple packages that all use pseudo-hashes.

       So don't do that.

Authors
       Matt Sergeant, matt@sergeant.org

       Stas Bekman (porting to mod_perl 2.0)

       A few concepts borrowed from "Stonehenge::Reload" by Randal Schwartz and "Apache::StatINC" (mod_perl 1.x) by Doug MacEachern and Ask Bjoern
       Hansen.

See Also
       "Stonehenge::Reload"

perl v5.8.0							    2002-06-15								 RELOAD(1)