Surviving Slashdot:
How to plan
for the deluge.

Magnatune’s
architecture:
linux/apache/mysql/php

What happened when
Slashdot hit.

1. Thousands of Apache
processes

2. Http Servers
unresponsive

3. Http Audio Streaming
not fast enough for real
time

Analysis & Solutions

Why is Yahoo so
“snappy” ?

By default, Web
browsers ask for every
image on every page
with “If-Modified-Since”.

Ironically, lots of small
graphics on a web page
is the least efficient use
of HTTP.

What if you could make
browsers not ask for
images that are
unchanging?

Trick #1:
use “Expires” HTTP header on
static graphics:
Expires: Thu, 15 Apr 2010 20:00:00 GMT

I did this by hacking the
C source code to my
HTTP server.

Is there a fast Apache
way to add an Expires:
header when returning
GIF/JPEGs?

next problem...

In many cases, HTTP
performance is
constrained by the
receiver, not the sender.

Large files take a long
time to be downloaded
by the requestor.

Each download uses up
an Apache process.

Apache Bench shows
great large-file
performance.

But Apache Bench isn’t a
useful metric with large
files in the real world.

The problem is the
“fork” based
architecture of Apache.

Thread-based HTTP
servers have the same
problem.

Apache has an
experimental “async”
mode -- this may be a
solution in the future.

Trick #2:
Use a dedicated async-
based HTTP server for
large files.

next problem...

PHP is handy.
But PHP is slow.

Apache Bench
Speed tests:
PHP: 9 pages/sec
HTML: 250 pages/sec

Trick #3:
Statically cache most
PHP pages into HTML.

Use Apache
“MultiViews”
option.

URLs shouldn’t
include .php or .html

ie:
http://x.com/mypage
could be PHP or HTML,
doesn’t matter.

Have a script regularly
HTTP GET most PHP
files, save as HTML and
delete the PHP.

Yields a 25x speed
increase.

end