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  }

  if ($f->seen_eos) {
    # we've seen the end of the data stream

    # Hier muss keine Ersetzung durchgeführt werden, da $context->{extra}
    # für richtige HTML Dokumente leer sein muss.

    # print any leftover data
    $f->print($context->{extra}) if( length $context->{extra} );
  }

  return Apache2::Const::OK;
}

1;

__END__

=head1 NAME

Apache2::ClickPath - Apache WEB Server User Tracking

=head1 SYNOPSIS

 LoadModule perl_module ".../mod_perl.so"
 PerlLoadModule Apache2::ClickPath
 <ClickPathUAExceptions>
   Google     Googlebot
   MSN        msnbot
   Mirago     HeinrichderMiragoRobot
   Yahoo      Yahoo-MMCrawler
   Seekbot    Seekbot
   Picsearch  psbot
   Globalspec Ocelli
   Naver      NaverBot
   Turnitin   TurnitinBot
   dir.com    Pompos
   search.ch  search\.ch
   IBM        http://www\.almaden\.ibm\.com/cs/crawler/
 </ClickPathUAExceptions>
 ClickPathSessionPrefix "-S:"
 ClickPathMaxSessionAge 18000
 PerlTransHandler Apache2::ClickPath
 PerlOutputFilterHandler Apache2::ClickPath::OutputFilter
 LogFormat "%h %l %u %t \"%m %U%q %H\" %>s %b \"%{Referer}i\" \"%{User-agent}i\" \"%{SESSION}e\""

=head1 ABSTRACT

C<Apache2::ClickPath> can be used to track user activity on your web server
and gather click streams. Unlike mod_usertrack it does not use a cookie.
Instead the session identifier is transferred as the first part on an URI.

Furthermore, in conjunction with a load balancer it can be used to direct
all requests belonging to a session to the same server.

=head1 DESCRIPTION

C<Apache2::ClickPath> adds a PerlTransHandler and an output filter to
Apache's request cycle. The transhandler inspects the requested URI to
decide if an existing session is used or a new one has to be created.

=head2 The Translation Handler

If the requested URI starts with a slash followed by the session prefix
(see L</"B<ClickPathSessionPrefix>"> below) the rest of the URI up to the next
slash is treated as session identifier. If for example the requested URI
is C</-S:s9NNNd:doBAYNNNiaNQOtNNNNNM/index.html> then assuming
C<ClickPathSessionPrefix> is set to C<-S:> the session identifier would be
C<s9NNNd:doBAYNNNiaNQOtNNNNNM>.

Starting with version 1.8 a checksum is included in the session ID. Further,
some parts of the information contained in the session including the checksum
can be encrypted. This both makes a valid session ID hard to guess. If an
invalid session ID is detected an error message is printed to the ErrorLog.
So, a log watching agent can be set up to catch frequent abuses.

If no session identifier is found a new one is created.

Then the session prefix and identifier are stripped from the current URI.
Also a potentially existing session is stripped from the incoming C<Referer>
header.

There are several exceptions to this scheme. Even if the incoming URI
contains a session a new one is created if it is too old. This is done
to prevent link collections, bookmarks or search engines generating
endless click streams.

If the incoming C<UserAgent> header matches a configurable regular
expression neither session identifier is generated nor output filtering
is done. That way search engine crawlers will not create sessions and
links to your site remain readable (without the session stuff).

The translation handler sets the following environment variables that
can be used in CGI programms or template systems (eg. SSI):

=over 4

=item B<SESSION>

the session identifier itself. In the example above
C<s9NNNd:doBAYNNNiaNQOtNNNNNM> is assigned. If the C<UserAgent> prevents
session generation the name of the matching regular expression is
assigned, (see L</"B<ClickPathUAExceptions>">).

=item B<CGI_SESSION>

the session prefix + the session identifier. In the example above
C</-S:s9NNNd:doBAYNNNiaNQOtNNNNNM> is assigned. If the C<UserAgent> prevents
session generation C<CGI_SESSION> is empty.

=item B<SESSION_START>

the request time of the request starting a session in seconds since 1/1/1970.

=item B<CGI_SESSION_AGE>

the session age in seconds, i.e. CURRENT_TIME - SESSION_START.

=item B<REMOTE_SESSION>