PR: 2365

  <!--#include virtual="header.html" -->

  <H1 ALIGN="CENTER">Apache Server Frequently Asked Questions</H1>

  <P>

  $Revision: 1.118 $ ($Date: 1998/05/30 01:27:25 $)

  $Revision: 1.119 $ ($Date: 1998/06/06 15:39:26 $)

  </P>

  <P>

  The latest version of this FAQ is always available from the main

  <P>

  Apache does <EM>not</EM> send automatically send a cookie on every

  response, unless you have re-compiled it with the

  <A HREF="../mod/mod_cookies.html"><SAMP>mod_cookies</SAMP></A>

  module.

  This module was distributed with Apache prior to 1.2.

  This module may help track users, and uses cookies to do this. If

  you are not using the data generated by <SAMP>mod_cookies</SAMP>, do

  not compile it into Apache. Note that in 1.2 this module was renamed

  to the more correct name

  <A HREF="../mod/mod_usertrack.html"><SAMP>mod_usertrack</SAMP></A>,

  and cookies

  have to be specifically enabled with the

  <A HREF="../mod/mod_usertrack.html"><SAMP>mod_usertrack</SAMP></A>

  module, and specifically enabled it with the

  <A HREF="../mod/mod_usertrack.html#cookietracking"

  ><SAMP>CookieTracking</SAMP></A>

  directive.

  This module has been in Apache since version 1.2.

  This module may help track users, and uses cookies to do this. If

  you are not using the data generated by <SAMP>mod_usertrack</SAMP>, do

  not compile it into Apache. 

  </P>

  <HR>

 </LI>

      it?  Why doesn't my server push work?</STRONG>

     </A>

  <P>

  In order to improve network performance, Apache buffers script output

  into relatively large chunks.  If you have a script that sends

  information in bursts (eg. as partial-done messages in a multi-commit

  database transaction or any type of server push), the client will 

  not necessarily get the output as the script is generating it.

  </P>

  <P>

  To avoid this, Apache recognizes scripts whose names begin with

  &quot;<SAMP>nph-</SAMP>&quot; as <EM>non-parsed-header</EM> scripts.

  That is, Apache won't buffer their output, but connect it directly to

  the socket going back to the client.

  </P>

  <P>

  While this will probably do what you want, there <EM>are</EM> some

  disadvantages to it:

  </P>

  <UL>

   <LI><STRONG>YOU</STRONG> (the script) are responsible for generating

     <STRONG>ALL</STRONG> of the HTTP headers, and no longer

     <EM>just</EM> the &quot;<SAMP>Content-type</SAMP>&quot; or

     &quot;<SAMP>Location</SAMP>&quot; headers

   </LI>

   <LI>Unless your script generates its output carefully, you will see a

    performance penalty as excessive numbers of packets go back and forth

   </LI>

  </UL>

  <P>

  As an example how you might handle the former (in a Perl script):

  </P>

  <P>

  <DL>

   <DD><CODE>if ($0 =~ m:^(.*/)*nph-[^/]*$:) {

    <BR>

        

    $HTTP_headers = 

    "HTTP/1.1 200 OK\015\012";

    <BR>

        

    $HTTP_headers .= 

    "Connection: close\015\012";

    <BR>

        

    print $HTTP_headers;

    <BR>

    }</CODE>

   </DD>

  </DL>

  </P>

  <P>

  and then follow with your normal non-<SAMP>nph</SAMP> headers.

  As of Apache 1.3, CGI scripts are essentially not buffered.  Every time

  your script does a "flush" to output data, that data gets relayed on to

  the client.  Some scripting languages, for example Perl, have their own

  buffering for output - this can be disabled by setting the <CODE>$!</CODE>

  special variable to 1.  Of course this does increase the overall number

  of packets being transmitted, which can result in a sense of slowness by 

  the end user.

  </P>

  <P>Note that in version 1.3, all CGI scripts will be unbuffered

  so the only difference between nph scripts and normal scripts is

  <P>Prior to 1.3, you needed to use "nph-" scripts to accomplish non-buffering.

  Today, the only difference between nph scripts and normal scripts is

  that nph scripts require the full HTTP headers to be sent.

  </P>

  <HR>