NAME
    ModPerl2::Tools - a few hopefully useful tools

SYNOPSIS
     use ModPerl2::Tools;

     ModPerl2::Tools::spawn +{keep_fd=>[3,4,7], survive=>1}, sub {...};
     ModPerl2::Tools::spawn +{keep_fd=>[3,4,7], survive=>1}, qw/bash -c .../;

     ModPerl2::Tools::safe_die $status;
     $r->safe_die($status);
     $f->safe_die($status);

     $content=ModPerl2::Tools::fetch_url $url;
     $content=$r->fetch_url($url);

INSTALLATION
     perl Makefile.PL
     make
     make test
     make install

DESCRIPTION
    This module is a collection of functions and methods that I found useful
    when working with "mod_perl". I work mostly under Linux. So, I don't
    expect all of these functions to work on other operating systems.

  Forking off long running processes
    Sometimes one needs to spawn off a long running process as the result of
    a request. Under modperl this is not as simple as calling "fork" because
    that way all open file descriptors would be inherited by the child and,
    more subtle, the long running process would be killed when the
    administrator shuts down the web server. The former is usually
    considered a security issue, the latter a design decision.

    There is already $r->spawn_proc_prog that serves a similar purpose as
    the "spawn" function. However, "spawn_proc_prog" is not usable for long
    running processes because it kills the children after a certain timeout.

   Solution
     $pid=ModPerl2::Tools::spawn \%options, $subroutine, @parameters;

    or

     $pid=ModPerl2::Tools::spawn \%options, @command_line;

    "spawn" expects as the first parameter an options hash reference. The
    second parameter may be a code reference or a string.

    In case of a code ref no other program is executed but the subroutine is
    called instead. The remaining parameters are passed to this function.

    Note, the perl environment under modperl differs in certain ways from a
    normal perl environment. For example %ENV is not bound to the C-level
    "environ". These modifications are not undone by this module. So, it's
    generally better to execute another perl interpreter instead of using
    the $subroutine feature.

    The options parameter accepts these options:

    keep_fd => \@fds
        here an array of file descriptor numbers (not file handles) is
        expected. All other file descriptors except for the listed and file
        descriptor 2 (STDERR) are closed before calling $subroutine or
        executing @command_line.

    survive => $boolean
        if passed "false" the created process will be killed when Apache
        shuts down. if true it will survive an Apache restart.

    The return code on success is the PID of the process. On failure "undef"
    or an empty string is returned.

    The created process is not related as a child process to the current
    apache child.

  Serving "ErrorDocument"s
    Triggering "ErrorDocument"s from a registry script or even more from an
    output filter is not simple. The normal way as a handler is

      return Apache2::Const::STATUS;

    This does not work for registry scripts. An output filter even if it
    returns a status can trigger only a "SERVER_ERROR".

    The main interface to enter standard error processing in Apache is
    "ap_die()" at C-level. Its Perl interface is hidden in Apache2::HookRun.

    There is one case when an error message cannot be sent to the user. This
    happens if the HTTP headers are already on the wire. Then it is too
    late.

    The various flavors of "safe_die()" take this into account.

    ModPerl2::Tools::safe_die $status
        This function is designed to be called from registry scripts. It
        uses Apache2::RequestUtil->request to fetch the current request
        object. So,

         PerlOption +GlobalRequest

        must be enabled.

        Usage example:

         ModPerl2::Tools::safe_die 401;
         exit 0;

    $r->safe_die($status)
    $f->safe_die($status)
        These 2 methods are to be used if a request object or a filter
        object are available.

        Usage from within a filter:

         package My::Filter;
         use strict;
         use warnings;

         use ModPerl2::Tools;
         use base 'Apache2::Filter';

         sub handler : FilterRequestHandler {
           my ($f, $bb)=@_;
           return $f->safe_die(410);
         }

        The filter flavor removes the current filter from the request's
        output filter chain.

  Fetching the content of another document
    Sometimes a handler or a filter needs the content of another document in
    the web server's realm. Apache provides subrequests for this purpose.

    The 2 "fetch_url" variants use a subrequest to fetch the content of
    another document. The document can even be fetched via "mod_proxy" from
    another server. However, fetching a document directly as with LWP for
    example is not (yet) possible.

    "ModPerl2::Tools::fetch_url" needs

     PerlOption +GlobalRequest

    Usage:

     $content=ModPerl2::Tools::fetch_url '/some/where?else=42';

     $content=$r->fetch_url('/some/where?else=42');

EXPORTS
    None.

SEE ALSO
    <http://perl.apache.org>

AUTHOR
    Torsten Förtsch, <torsten.foertsch@gmx.net<gt>

COPYRIGHT AND LICENSE
    Copyright (C) 2010 by Torsten Förtsch

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

