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Re^3: CGI::Application... flushing output to browser?

by Anonymous Monk
on May 04, 2012 at 09:36 UTC ( [id://968899]=note: print w/replies, xml ) Need Help??


in reply to Re^2: CGI::Application... flushing output to browser?
in thread CGI::Application... flushing output to browser?

Post some code :) ( How do I post a question effectively? and all that )

Also, even though jfroebe and antirice have visited this year, see also on necromancy (reviving old threads)

  • Comment on Re^3: CGI::Application... flushing output to browser?

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Re^4: CGI::Application... flushing output to browser?
by Anonymous Monk on May 04, 2012 at 11:06 UTC

    Sorry about that. See below. It's a bit long, but it's a complex issue, and I can't find a shorter way of expressing all the things I have tried. 

    package SimpleApp;
use base 'CGI::Application';
use strict;

###################################################################
# 
# This script is an attempt at "subverting" CGI::Application into
# running modes that print HTML directly to STDOUT, instead of
# cumulating it into a string and returning it.
#
# It seems possible to do that, as long as you don't use the 
# Authentication plugin, as illustrated below.
#
# In this App, we have two versions of each of the run modes.
#
#    The 'print_at_very_end' version implements the standard 
#    CGI::Application  
#    approach, namely, it collects the HTML output in a string 
#    variable, and returns it.
#
#    The 'print_as_you_go' version prints the HTML directly to 
#    STDOUT, as soon as it is generated. These versions of the run 
#    modes need to print headers themselves instead of letting 
#    CGI::Application, because the later generates the headers AFTER 
#    the body method has been called (and it prepends them to the body
+).
#    But by that time, it's too late to print the headers, because
#    the body has already been printed to STDOUT.
#
# To switch between the 'print_as_you_go' and 'print_at_very_end'
# versions, simply set $print_when to 'at_very_end' or 'as_you_go'.
#
# You can also run the application with, or without Authentication plu
+gin.
# Simply set $use_authentication to 1 or undef;
#
# Try the following scenarios.
#
# Scenario 1: 'print_at_very_end', with authentication
# - Set $print_when = 'at_very_end' and $use_authentication = 1
# - Clear cookies
# - go to simple_app.cgi
# - login as u=guest, p=1234
# - notice how the Welcome page takes about 2 secs before it displays 
#   anything (because it sleeps for 1 sec between generating each line
+ 
#   and doesn't print anything until all the lines have been generated
+)
# - click on Help link
# - notice how you're brought to the Help page without being asked
#   to login again
#
# Scenario 2: 'print_as_you_go', without authentication
# - Set $print_when = 'as_you_go' and $use_authentication = undef
# - Clear cookies
# - go to simple_app.cgi
# - no need to login (there is no authentication)
# - notice how the content of the Welcome page starts being displayed
#   immediatly, without the 2 secs delay.
# - click on Help link
# - notice how you're brought to the Help page without being asked
#   to login again.
#
# Scenario 3: 'print_as_you_go', with authentication
# - Set $print_when = 'as_you_go' and $use_authentication = 1
# - Clear cookies
# - go to simple_app.cgi
# - login as u=guest, p=1234
# - notice how the content of the Welcome page starts being displayed
#   immediatly, without the 2secs delay.
# - click on Help link
# - notice how you're asked to login again.
# - login again as u=guest, p=1234
# - Notice how you are brought to the Welcome page again, 
#   as opposed to the Help page you were trying to go to.
# - This seems to be due to the fact that the session cookies
#   were not output correctly (they are part of the headers,
#   and we are mocking around with them in non-standard ways.)
#
###################################################################

my $print_when;
BEGIN {
#    #$print_when = 'at_very_end';
    $print_when = 'as_you_go';

    my $use_authentication = 1;
#    my $use_authentication = undef;

    if ($use_authentication) {
        use CGI::Application::Plugin::Authentication;
        SimpleApp->authen->config(
               DRIVER => [ 'Generic', { guest => '1234'} ],
               POST_LOGIN_RUNMODE => 'welcome',
               LOGOUT_RUNMODE => "logout"
         );
        SimpleApp->authen->protected_runmodes(':all');    
    }
}

sub setup {
     my $self = shift;
     $self->start_mode('welcome');
     $self->run_modes(
             'welcome' => "welcome_print_$print_when",
             'logout' => "logout_print_$print_when",
             'help' => "help_print_$print_when",
             'strea_file' => "stream_file"
     );
     $self->mode_param('dlg');
}

sub welcome_print_as_you_go {
     my $self = shift;
          
    $self->header_type("none");
    $| = 1;

    print $self->query()->header();

     # Get CGI query object
     my $q = $self->query();

     print $q->start_html(-title => 'Welcome to SimpleApp!');
     
     my $user_name = $self->authen->username;
     print $q->h3("Hello, '$user_name'");

     my $sleep_for = 1;
     print $q->p("The next few lines will be printed at $sleep_for sec
+s intervals.");
     for (my $ii=0; $ii < 2; $ii++) {
         print "Line $ii<br/>\n";
         sleep($sleep_for);
     }
     
     print $q->p()."\n";
     print "<a href=\"simple_app.cgi?dlg=help\">Help</a><br/>\n";
     print "<a href=\"simple_app.cgi?authen_logout=1\">Logout</a><br/>
+\n";

              
     print $q->end_html();

     return '';
}


sub welcome_print_at_very_end {
     my $self = shift;

     # Get CGI query object
     my $q = $self->query();

     my $output = '';
     $output .= $q->start_html(-title => 'Welcome to SimpleApp!');
     
     my $user_name = $self->authen->username;
     $output .= $q->h3("Hello, '$user_name' (print as batch)");

     my $sleep_for = 1;
     $output .= $q->p("The next few lines will be printed at $sleep_fo
+r secs intervals.");
     for (my $ii=0; $ii < 2; $ii++) {
         $output .= "Line $ii<br/>\n";
         sleep($sleep_for);
     }
     
     $output .=  $q->p()."\n";
     $output .=  "<a href=\"simple_app.cgi?dlg=help\">Help</a><br/>\n"
+;
     $output .=  "<a href=\"simple_app.cgi?authen_logout=1\">Logout</a
+><br/>\n";
              
     $output .= $q->end_html();

     return $output;
}

sub logout_print_at_very_end {
    my ($self) = @_;

     # Get CGI query object
     my $q = $self->query();

     my $output = '';
     $output .= $q->start_html(-title => 'You have been logged out!');
     
     $output .= $q->h3("You have been logged out.");
     
     $output .=  $q->p()."\n";
     $output .=  "<a href=\"simple_app.cgi?dlg=welcome\">Home</a><br/>
+\n";
     $output .=  "<a href=\"simple_app.cgi?dlg=help\">Help</a><br/>\n"
+;

     $output .= $q->end_html();

     return $output;
}

sub logout_print_as_you_go {
    my ($self) = @_;

    $self->header_type("none");
    $| = 1;

     # Get CGI query object
     my $q = $self->query();
     
     print $self->query()->header();

     my $output = '';
     print $q->start_html(-title => 'You have been logged out!');
     
     print $q->h3("You have been logged out.");
     
     print  $q->p()."\n";
     print  "<a href=\"simple_app.cgi?dlg=welcome\">Home</a><br/>\n";
     print  "<a href=\"simple_app.cgi?dlg=help\">Help</a><br/>\n";

     print $q->end_html();

     return $output;
}

sub help_print_as_you_go {
    my ($self) = @_;
    
    $self->header_type("none");
    $| = 1;

     my $q = $self->query();
     print $q->header();

     print $q->start_html(-title => 'SimpleApp Help');
     
     my $user_name = $self->authen->username;
     print $q->h3("Dear '$user_name', how may I help you? (print as yo
+u go)");

     print "<a href=\"simple_app.cgi?dlg=welcome\">Home</a><br/>\n";
     print "<a href=\"simple_app.cgi?authen_logout=1\">Logout</a><br/>
+\n";
              
     my $sleep_for = 1;
     print $q->p("The next few lines will be printed at $sleep_for sec
+s intervals.");
     for (my $ii=0; $ii < 2; $ii++) {
         print "Line $ii<br/>\n";
         sleep($sleep_for);
     }
              
     print $q->end_html();

     return '';
}

sub help_print_at_very_end {
     my $self = shift;
     
     # Get CGI query object
     my $q = $self->query();

     my $output = '';
     $output .= $q->start_html(-title => 'SimpleApp Help');
     
     my $user_name = $self->authen->username;
     $output .= $q->h3("Dear '$user_name', how may I help you? (print 
+as batch)");

     my $sleep_for = 1;
     $output .= $q->p("The next few lines will be printed at $sleep_fo
+r secs intervals.");
     for (my $ii=0; $ii < 2; $ii++) {
         $output .= "Line $ii<br/>\n";
         sleep($sleep_for);
     }
     
     $output .=  $q->p()."\n";
     $output .=  "<a href=\"simple_app.cgi?dlg=welcome\">Home</a><br/>
+\n";
     $output .=  "<a href=\"simple_app.cgi?authen_logout=1\">Logout</a
+><br/>\n";
              
     $output .= $q->end_html();

     return $output;
}

sub stream_file {
    my ($self) = @_;
    
    
}

1;  # Perl requires this at the end of all modules

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[reply]
[d/l]

      Hmm, regarding buffering/autoflush/$|=1, adding  eval { Apache2::RequestUtil->request->rflush; }; before sleep works for me

      but according to the docs  local $|=1 should have also worked, but I don't have the latest mod_perl2/apache2 here :/

      Regarding the missing cookies, I fear you're right , the module definitely needs updating , bummer :(

[reply]
[d/l]
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