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

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

         # 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 { ... }

       "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 modi-

       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 envi-
       ronment 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

       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 hap-
       pen 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

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 modules in %INC, which will significantly slow every-
           thing down.

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

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

       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 interpreter will
       have its own copy of the syntax tree for the reloaded subroutines.

       The short summary of this is: Don't use pseudo-hashes. They are depre-
       cated 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.

       Matt Sergeant,

       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

See Also

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