NAME
    Apache::Handlers

SYNOPSIS
    In code:

      use Apache::Handlers qw(CLEANUP);

      our $global;
      my $session : PerlCleanupHandler;

      CLEANUP {
        our $global = undef;
      };

    In httpd.conf:

      PerlModule Apache::Handlers
      PerlChildInitHandler Apache::Handlers
      PerlPostReadRequestHandler Apache::Handlers
      <Perl>
        Apache::Handlers -> reset;
      </Perl>

DESCRIPTION
    "Apache::Handlers" provides two different methods of declaring when code
    snippets should be run during the Apache request phase.

    The code defined with the constructs provided by this module do not
    directly affect the success or failure of the request. Thus, this module
    does not provide a replacement for content, access, or other handlers.

    The code is executed in the order it is encountered except for
    "CHILDEXIT", "CLEANUP", "PerlChildExitHandler", and "PerlCleanupHandler"
    code. These are executed in the reverse order, similar to the pairing of
    "BEGIN" and "END" blocks.

    The block construct or attribute must be run before the phase it refers
    to. Otherwise, it won't be run in that phase. The phases are run in the
    following order:

    CHILDINIT TRANS HEADERPARSER ACCESS AUTHEN AUTHZ TYPE FIXUP CONTENT LOG
    CLEANUP CHILDEXIT

    The RESTART phase is not an actual Apache request phase and has no
    effect after the server has started. It is used to define code that
    should run during the server startup phase when Apache reads the server
    configuration the second time or is gracefully (or not so gracefully)
    restarted. It should be used to clean up so the second configuration
    process won't duplicate information or cause errors.

    If this module is called during the ChildInit phase, then it will only
    call that code associated with CHILDINIT blocks. Otherwise, the
    CHILDINIT code will be run at the first opportunity (basically, the
    first request made of the child process). Thus the two Perl*Handler
    configuration directives in the Synopsis.

  Running without mod_perl

    When developing outside mod_perl, all code associated with CHILDINIT,
    TRANS, HEADERPARSER, ACCESS, AUTHEN, AUTHZ, TYPE, FIXUP, and CONTENT is
    run in an "INIT" block. All code associated with LOG, CLEANUP, and
    CHILDEXIT is run in an "END" block.

  Block Constructs

    The following allow for blocks of code to be run at the specified phase.
    Note that these are subroutines taking a single code reference argument
    and thus require a terminating semi-colon (;). They are named to be like
    the BEGIN, END, etc., constructs in Perl, though they are not quite at
    the same level in the language.

    If the code is seen and handled before Apache has handled a request, it
    will be run for each request. Otherwise, it is pushed on the handler
    stack, run, and then removed at the end of the request.

    These are named the same as the Apache/mod_perl configuration directives
    except the "Perl" and "Handler" strings have been removed and the
    remainder has been capitalized.

    ACCESS
    AUTHEN
    AUTHZ
    CHILDEXIT
    CHILDINIT
    CLEANUP
    CONTENT
    FIXUP
    HEADERPARSER
    LOG
    POSTREADREQUEST
    RESTART
    TRANS
    TYPE
  Attributes

    If Attribute::Handlers is available, then the following attributes are
    available (N.B.: Attribute::Handlers requires Perl 5.6.0). These are
    named the same as the Apache/mod_perl configuration directives.

    If the attribute argument is a constant value (non-CODE reference), then
    the variable is assigned that value. Otherwise, it is assigned the value
    that the CODE reference returns.

    If the attribute is being applied to a subroutine, then that subroutine
    is called during that phase. For example, the following two snippets
    result in the same code being run at the same time.

     my $something  = sub : PerlChildExitHandler {
       print "We did it!\n";
     };

     sub something : PerlChildExitHandler {
       print "We did it!\n";
     };

    When an attribute is applied to a subroutine, the argument is ignored.

    When the attribute argument is itself a CODE reference, the referent
    (the variable the attribute applies to) is passed as a reference:

     my $global : PerlChildInitHandler(sub { print "global: $$_[0]\n" });

    This will print the value of $global and set it equal to 1 (or the value
    of the print statement).

    PerlAccessHandler
    PerlAuthenHandler
    PerlAuthzHandler
    PerlChildInitHandler
    PerlChildExitHandler
    PerlCleanupHandler
    PerlFixupHandler
    PerlHandler
    PerlHeaderParserHandler
    PerlLogHandler
    PerlPostReadRequestHandler
    PerlRestartHandler
    PerlTransHandler
    PerlTypeHandler
  Other Methods

    dump
        This will dump the current set of code references and return the
        string. This uses Data::Dumper.

    reset
        This will clear out all previously set code. This should only be
        used in the "startup.pl" or equivalent so that code doesn't get run
        twice during a request (when it should only be run once). This will
        also run any RESET blocks that have been defined.

    run_phase
        Given a list of phases (using the names for the block constructs
        above), this will run through the code for that phase, "die"ing
        (outside mod_perl) or logging (if in mod_perl) if there is an error.
        For example,

          run_phase( qw: CONTENT LOG CLEANUP : );

        will run any code associated with the CONTENT, LOG, and CLEANUP
        phases.

CAVEATS
    Caveats are things that at first glance might be bugs, but end up
    potentially useful. So I am going to make this section into a kind of
    cookbook for non-obvious uses for these potential bugs.

  Authentication and Authorization

    Be aware that these two phases only run if Apache has reason to believe
    they are needed. This can be a bit handy since the following snippet
    should tell you if the authentication phase was run. Of course, if an
    authentication handler runs before this and returns OK, then this may
    not run.

      my $authentication_ran : PerlTransHandler(0) PerlAuthenHandler(1);

      LOG {
        if($authentication_ran) {
          # log something special
        }
      };

  Errors

    If code causes an error (such that an eval would set $@), then the
    request will throw a SERVER_ERROR and write $@ to either STDERR (if not
    in mod_perl and there is no "die" handler, such as the Error module) or
    to the Apache error log with a log level of debug.

  "Use"ing modules

    Any of the block constructs or attributes provided by this module that
    are used in the body of a module that is brought in via the "use"
    keyword will be considered to take place before the child is spawned.
    This means that any code designated to run during a particular phase
    will be run at the appropriate time as if the module had been loaded
    during the server startup.

    Modules can now rest assured that using a CLEANUP block in their file
    will mean that code is run at the end of every request, even if the
    module was loaded in the child process and not during server startup.

    This is done by looking for code run during the BEGIN phase.

BUGS
    Unlike caveats, bugs are features that are undesirable and/or get in the
    way of doing something useful. I'm sure there are some. Please let me
    know when you find them.

  Security

    There is no way (currently) to limit registration of code for later
    processing during a particular phase. Ideas are welcome for how this
    should be designed.

SEE ALSO
    the Apache manpage, the Attribute::Handlers manpage, the Data::Dumper
    manpage.

AUTHOR
    James G. Smith <jsmith@cpan.org>

COPYRIGHT
    Copyright (C) 2002 Texas A&M University. All Rights Reserved.

    This module is free software; you can redistribute it and/or modify it
    under the same terms as Perl itself.

