[Gllug] Slightly OT: Apache mod_throttle

Tue Aug 20 09:58:55 UTC 2002

Flash (saviour of the universe), sorry this one's late.

On Tue, 2002-08-13 at 09:55, Flash Wilson wrote:
> I am running apache 1.3.26 on redhat 6.2.

[shnip]

> I am told this may be because mod_throttle is a handler, and
> CGIs already use another one. Not sure tho - cant find anything
> to assist/confirm/deny on that.

That's true, I think, on Apache 1.3.x. Not so with Apache 2, though,
where everything's a filter, like ISAPI-land but more so. So you can, in
theory, have a CGI producing PHP code which gets executed to produce XML
which gets translated into HTML. Sick and twisted, eh?

> Anyone able to advise on a solution to throttle access to this
> CGI? 

Apache 2 is probably your best bet, but you could also run a second
Apache instance to handle this CGI, and let that go bang happily,
couldn't you? Obviously on a different port, although you could proxy it
for the changeover.

> Blocking offenders is not an option, and rewriting the CGI is
> a last resort only (or I wouldnt bother asking).

Or something like this, which you could use to wrap errant scripts, and
which would tell the browser to come back later. Might be worth a shot.

#!/usr/bin/perl

$maxinstance = 5;
$name = "fish";
$myurl = "http://somehost.org/cgi-bin/this-script"; ## Not used, but
maybe should be.

$execed = 0;
for( $i=0; $i<$maxinstance; ++$i ) {
   if( sysopen( TMP, "/var/lock/$name-$i", O_RDWR|O_CREAT|O_EXCL ) ) {
      #  fork, exec, wait - or system() if you're feeling frisky.
      $execed = 1
      close( TMP );
      unlink( "/var/lock/$name-$i" );
      break;
   }
}

unless( $execed ) {
   print "Content-Type: text/html\nRefresh: 10\n\n";
   # Dunno whether "Refresh" header here works, or whether it needs URL,
or to be in a META tag, or both.
   print "<html><head><title>Please Wait</title></head><body><h1>Please
Wait</h1><p>This resource is currently very busy. Your browser will
automatically retry after 10 seconds.</p></body></html>\n";
}
# END

Dave.

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