Battling the “Slashdot Effect”

I’ve always wondered what exactly one can do to combat high volume traffic from slashdot, digg, reddit and other populate news sites – known commonly as the Slashdot effect. The other day, I got a first hand opportunity to find out.  One of our clients sites was posted to multiple news site – so what better way to try out and see what works in a real life slashdotting.  Below, is the solution I ended up with that seemed to remove a significant amount of strain from the server without costing any additional money.

As I was doing some research, I came across some creative uses of the Coral CDN – and I have previously used lighttpd for high volume sites – so I put the two together. For those of you that don’t know about Coral CDN, its a peer-to-peer content distribution network. To take advantage of the CDN its easily – simply append to the end of any dns name and that’s it!  Since the site I was dealing with was fully dynamic, I did not have a lot of options that could be quickly implemented.

Once you get lighttpd setup, here are the example config bits to setup and perform the redirect:

# make sure this isn't CoralCache requesting content
$HTTP["useragent"] !~ "^CoralWebPrx" {
    # make sure that this wasn't sent back to us from CoralCache
    $HTTP["querystring"] !~ "(^|&)coral-no-serve$" {
        url.redirect = ( "^/.*" => "$0" )

The above will redirect all requests that do not have the Coral CDN user agent. It’s important to add this or else you’ll get a redirect loop.  Also – make sure you enable the "rewrite" and "redirect" server modules. 

For those of you that are using apache, you can add rules similiar to:

RewriteEngine On
RewriteCond %{HTTP_USER_AGENT} !^CoralWebPrx
RewriteRule ^(.*)$$1 [R,L]

In the end, caching, static pages, and load balancing is your best bet. But if your in a bind, lighttpd and Coral CDN will do the trick!