This document discusses techniques for building scalable websites with Perl, including: 1) Caching at various levels (page, partial page, and database caching) to improve performance and reduce load on application servers. 2) Using job queuing and worker processes to distribute processing-intensive tasks asynchronously instead of blocking web requests. 3) Leveraging caching and queueing libraries like Cache::FastMmap, Memcached, and Spread::Queue to implement caching and job queueing in Perl applications.

1. Building Scalable Websites with Perl
Perrin Harkins
Plus Three (http://plusthree.com/)

2. Who is doing it?
• Yahoo
– Overture
• Amazon
– IMDB
• InterActiveCorp
– Ticketmaster
– CitySearch

3. How are they doing it?
• Not just hardware
• Basic techniques

4. Things we won't be covering
• mod_perl tuning
– http://perl.apache.org/
• DBI tuning
– http://search.cpan.org/~timb/
• hardware

5. Caching

6. Page-Level Caching
• Best performance
• Pre-generate from batch job
page
batch
cache data
job
web
client
server

7. wget
wget ­­mirror ­­convert­links
­­html­extension ­­reject gif,jpg,png
­­no­parent
http://app­server/dynamic/pages/
wget
page
cache
web app
client data
server server

8. Generate-On-Demand
data
web mod_proxy app
client server cache server

9. mod_proxy
ProxyRequests Off
ProxyPass /dynamic/stuff http://app­
server/
ProxyPassReverse /dynamic/stuff
http://app­server/
CacheRoot "/mnt/proxy­cache"
CacheSize 500000
CacheGcInterval 12
CacheMaxExpire 36
CacheDefaultExpire 2

10. Intercepting 404 Errors
ErrorDocument 404 /page/generator
web page
client
server cache
404
handler data

11. Partial-Page Caching
2 hours
5 minutes
24 hours

12. Mason cache
my $result = $m­>cache­>get(
$search_term
);
if (!defined($result)) {
$result = run_search($search_term);
$m­>cache­>set($search_term,
$result,
'30 min');
}

13. Cache::FastMmap
our $Cache = Cache::FastMmap­>new(
cache_size => '500m',
expire_time => '30m',
);
$Cache­>set($key, $value);
my $value = $Cache­>get($key);

14. Memcached
our $Memd = Cache::Memcached­>new({
'servers' => [
"10.0.0.15:11211","10.0.0.15:11212",
"10.0.0.17:11211",
[ "10.0.0.17:11211", 3 ]
],
'debug' => 0,
'compress_threshold' => 10_000,
});
$Memd­>set($key, $value, 5*60 );
my $value = $Memd­>get($key);

15. Job Queuing

16. Get in Line

17. “search in progress”
web
client
server fork worker
redirect
web done
client reload worker
server yet?
result
http://www.stonehenge.com/merlyn/WebTechniques/col20.html

18. Spread::Queue client
use Spread::Queue::Sender;
my $sender = Spread::Queue::Sender­>new(
"myqueue"
);
$sender­>submit(
"myfunc", { name => "value" }
);
my $response = $sender­>receive();

19. Spread::Queue worker
use Spread::Queue::Worker;
my $worker = Spread::Queue::Worker­>new("myqueue");
$worker­>callbacks(
myfunc => &myfunc,
);
$SIG{INT} = &signal_handler;
$worker­>run;

20. Spread::Queue worker
sub myfunc {
my ($worker, $originator, $input) = @_;
my $result = {
response => "I heard you!",
};
$worker­>respond($originator, $result);
}

21. Resources
• “Computer Science and Perl Programming”
• “Mastering Algorithms with Perl”
• “Patterns of Enterprise Application
Architecture” by Martin Fowler
• http://oreillynet.com/

22. Thanks!
• Craig McLane and Adam Sussman of
Ticketmaster Online
• Zack Steinkamp of Yahoo