1. Using Apache as an
Application Server
Phillip J. Windley, Ph.D.
Founder and CTO
Kynetx

2. Assumptions
You’ve heard of Apache
You’ve heard of Perl
You’d like to build Web applications with less
effort

3. Anti-Assumptions
You’re familiar with mod_perl
You’re an Apache expert
You know what an application ser ver is and
why you’d want one

4. Application Server
Program that supplies support for running
applications:
Process and thread management
Security
Logging
Interprocess communication
Request dispatching

5. Popular Application Ser vers
You might have heard of
Tomcat
JBoss
WebLogic
WebSphere

6. Application Server Benefits
Flexibility through indirection (intermediary)
Resource management
Focused developer roles
Maintainability
Security
Scalability
Feature augmentation

7. Kynetx

8. Context automation
services to link tasks
across multiple Web-sites

9. Dynamically rearrange the
DOM (post-delivery) based
on client supplied rules, Web
services, and browser
context

10. Rule Language
rule frequent_archive_visitor is active {
select using "/archives/d+/d+/" setting ()
pre {
c = counter.archive_pages;
}
if counter.archive_pages > 2 within 3 days then {
replace_html("prize_div",
"You win the prize! You've seen " +
c +
" pages from the archives!")
}
fired {
clear counter.archive_pages;
} else {
counter.archive_pages += 1 from 1;
}
}

11. Kynetx Information Flow

12. We need a rule
interpreter that
dynamically serves
Javascript

13. Rule execution must
be as fast as possible

14. Amazon AWS
deployment and
scaling a necessity

15. Possible Architectures
Standard Web application
Custom HTTP server
Apache module

16. Architecture Decisions
Implement rule interpreter as an
Apache module
No database for scalability
No session pinning
Store rules in versioned repository

17. Detailed Architecture

18. Apache as an
Application Server

19. Apache
Fast and efficient
Portable
Well supported
Won’t go away (open source)
Stable and reliable
Plenty of features
Extensible
Easy to administer

20. Apache Modules

21. Modules are NOT CGI Programs
Modules run inside the Apache process
architecture
Modules have access to and can replace
all Apache ser vices
Uses the ser ver API - not an embedded
interpreter
Access to every part of the HTTP
request lifecycle

22. Apache Server Lifecycle

23. HTTP Request Lifecycle

24. We’ve got both kinds:
C & Perl!

25. Apache Application Ser vices
Configuration
Process and thread management
Security
Logging
Interprocess communication
Request dispatching

26. Configuration Support
Via Apache configuration file
Setting variables that can be seen in Perl
$r->dir_config('memcached_hosts')

27. Configuration
<LocationMatch /kobj/>
# env var to turn on rule logging
PerlSetEnv KOBJ 1
# host names
PerlSetVar init_host init
PerlSetVar log_host logger
PerlSetVar action_host cs
PerlSetVar frag_host frag
# mode => development, production, test
PerlSetVar run_mode development
PerlSetVar memcached_hosts 192.168.2.2
PerlAddVar memcached_hosts 192.168.2.3
SetHandler perl-script
PerlHandler Kynetx # Perl module name
</LocationMatch>

28. Process & Thread Management
Apache 2.X uses multi-processing modules
(MPMs) to provide a flexible way to change the
execution model
prefork - Apache 1.3
worker - Hybrid, based on pthreads
OS specific - Windows, BeOS, etc.
perchild - virtual hosts with custom UID’s

29. Process & Thread Management
<IfModule prefork.c>
StartServers 5
MinSpareServers 8
MaxSpareServers 15
MaxClients 150
MaxRequestsPerChild 0
</IfModule>

30. Apache manages the
processes

31. Start with one
process model and
switch to another
later

32. Security
Apache HTTP access, authentication, and
authorization (AAA) isn’t very good for
people
HTTP AAA works fine for machines (usually)
Standard
mod_auth
mod_access
You can also override the AAA phases of the
HTTP request cycle

33. Avoid AAA code in
your application

34. Interprocess Communication
Lots of Perl Modules
IPC::SysV
IPC::Shareable
IPC::Semaphore
IPC::ShareLite
Cache::Cache
Apache::Session

35. Apache::Session

36. Apache::Session Example
my $mem_servers =
Kynetx::Memcached::get_memcachedb_servers();
tie %{$session}, 'Apache::Session::Memcached', $cookie, {
Servers => $mem_servers,
NoRehash => 1,
Readonly => 0,
Debug => 1,
CompressThreshold => 10_000
};
return $session;

37. Logging
Apache has a great logging facility
Use the standard Apache logging
commands
Apache2::Log

38. Logging
LogFormat "%h %t %{TOTAL_SECS}e %{SITE}e %{TXN_ID}e "%{CALLER}e" %
{SID}e "%{REFERER}e" "%{TITLE}e" [%{RULE_NAMES}e] [%{RESULTS}e] [%
{ACTIONS}e] [%{TAGS}e] [%{LABELS}e] " KOBJ
CustomLog "|/web/sbin/cronolog --period=5 --symlink=/web/logs/
kynetx_log /web/logs/kynetx/KOBJ-%Y%m%d-%H%M.log" KOBJ env=KOBJ

39. Logging
$r->subprocess_env(SITE =>
$request_info->{'site'});
$r->subprocess_env(RULE_NAMES =>
join(',', @{ $rule_env->{'names'}}));
$r->subprocess_env(RESULTS =>
join(',', @{ $rule_env->{'results'}}));

40. Request Dispatching
Request dispatching says what to do for
each URL or URL pattern
Turns out that Apache is really good at this
Request dispatching is known as “routes” in
Rails

41. Dispatch Example
Translate
http://example.com/news/20021031/09/index.html
to
http://example.com/perl/news?
date=20021031;id=09;page=index.html
before news sees it.

42. Three Methods
Use configuration file
Use mod_rewrite
Use custom Translation stage handler
You can do anything you want here

43. Request Dispatching Example
<LocationMatch /kobj/>
SetHandler perl-script
PerlHandler Kynetx # Perl module name
</LocationMatch>
<LocationMatch /js/>
SetHandler perl-script
PerlHandler Kynetx::KOBJ # Perl module name
</LocationMatch>
<LocationMatch /cb/>
SetHandler perl-script
PerlHandler Kynetx::Callbacks # Perl module name
</LocationMatch>

44. What’s Missing?
Event monitoring
Timers
Long running processes

45. Other Tools You Might Use
mod_header
mod_deflate
Authentication modules
Authorization modules

46. The End
46

47. Contact Information
Contact me
phil@windley.org
www.windley.com
www.kynetx.com
Questions?