Date:         Sat, 24 May 1997 00:57:58 +0100
Reply-To: Discussion about the Apache ModPerl Module
              <MODPERL@LISTPROC.ITRIBE.NET>
Sender: Discussion about the Apache ModPerl Module
              <MODPERL@LISTPROC.ITRIBE.NET>
From: Rob Hartill <robh@IMDB.COM>
Subject:      <Perl></Perl> ideas
To: MODPERL@LISTPROC.ITRIBE.NET
X-UIDL: 77f3b370bb0d0f3738c7a78c27347e81

Here are some ideas that excited Douig enough to tweak mod_perl to
do new tricks for me. Doug asked me to share the ideas witht he list,
so here they are.

I'll use hypothetical examples for things I expect to deploy sometime
soon.

I've have multiple servers with very different jobs and until now they've
had to use different conf/ files to make them behave in different ways.

====================================
Here's an example on changing KeepAlive:

<Perl>
 if (`hostname` =~ /machine1/) {
        $KeepAlive  = 10;
        $KeepAliveTimeout = 10;
 } else {
        $KeepAlive  = 3;
        $KeepAliveTimeout = 1;
 }
 1;
</Perl>

A server that does lots of gif serving and doesn't mind spawning lots of
httpd processes can afford a longer KeepAliveTimeout and also let
users hog a single process for longer. In general, I much prefer keeping
the KeepAlive settings low so as to avoid spawning/maintaining the extra
httpd's to make up for those that are being hogged.

=====================================

Having different tasks for different servers, we can preload different
Modules:

<Perl>
 unshift(@INC, "/usr/local/httpd/scripts/");

 my $me = `hostname`;
 if ($me =~ /machine1/) {
        $PerlScript  = "/dev/null";
        @PerlModule = qw(Imdb::PreRequest Imdb::ErrorDocuments Imdb::Foo);
 } else {
        $PerlScript = "/usr/local/httpd/scripts/Main.pm";
        @PerlModule = qw(Imdb::PreRequest Imdb::ErrorDocuments Imdb::Bar Imdb::Baz);
 };
 1;
</Perl>

======================================

For different servers, adjust the various process spawning settings.

<Perl>

 my $me = `/bin/hostname`;
 if ($me =~ /(machine2|machine7)/) {
        $MinSpareServers  = 3;
        $MaxSpareServers  = 5;
        $StartServers     = 3;
        $MaxClients       = 30;
 } elsif ($me =~ /machine5/) {
        $MinSpareServers  = 20;
        $MaxSpareServers  = 40;
        $StartServers     = 20;
        $MaxClients       = 80 ;
 } elsif ($me =~ /(machine4)/) {
        $MinSpareServers  = 2;
        $MaxSpareServers  = 3;
        $StartServers     = 1;
        $MaxClients       = 10 ;
 } else {
        $MinSpareServers  = 5;
        $MaxSpareServers  = 6;
        $StartServers     = 4;
        $MaxClients       = 25;
 }
 1;
</Perl>

I have mirror sites running on different (but binary compatible) machines.
Some need more protection that others.

===================================

I also have a need for VirtualHost configuration that would require
tons of replication of basically the same information. With a loop
it's much easier and with conditional statements I can specify vhosts
only for the affected machines:

<Perl>

 my $me = `/bin/hostname`;
 my @vhosts = ();
 my $h;

 if ($me =~ /machine[1234]/) {
        @vhosts = qw(one two three four);
 } elsif ($me =~ /machine5/) {
        @vhosts = qw(foo bar);
 }

 for $h (@vhosts) {
      %{$VirtualHost{"$h.imdb.com"}} = (
         "ServerName" => "$h.imdb.com",
         "LogFormat"  => qq('%h ($h) %u %t "%r" %>s %b "" "%{User-agent}i"');
      );
 }
 1;
</Perl>


I define a different set of vhosts for different machines and initialise
their "ServerName" without writing them out one by one. I also use Apache's
LogFormat directive to embed the hostname in the logfiles (the '($h)' part).

==========


Anyway, I think you can see that for people with multiple servers that
need to be configured differently, mod_perl's new <Perl></Perl> features
are the key.

I hope to deploy some of these new config files in the next fews days.
I'll probably come up with some other uses for <Perl></Perl> now that
the potential is there to have dynamically reconfigurable config files.

thanks Doug!.


--
Rob Hartill                              Internet Movie Database (Ltd)
http://www.moviedatabase.com/   .. a site for sore eyes.