Plack provides a common interface called PSGI (Perl Server Gateway Interface) that allows Perl web applications to run on different web servers. It includes tools like Plackup for running PSGI applications from the command line and middleware for adding functionality. Plack has adapters that allow many existing Perl web frameworks to run under PSGI. It also provides high performance PSGI servers and utilities for building and testing PSGI applications.

1. Plack
Superglue for Perl Web Frameworks
Tatsuhiko Miyagawa
Perl Oasis 2010

2. Tatsuhiko Miyagawa
• Japanese, lives in San Francisco
• Works at Six Apart
• 170+ CPAN modules (id:MIYAGAWA)
• @miyagawa
• bulknews.typepad.com

3. Background

4. 40 slides of why we need Plack.
May I fast-forward them?
(since Stevan spoiled)

5. Web Frameworks

6. Maypole Mason Mojo Sledge Catalyst Spoon PageKit
AxKit Egg Gantry Continuity Solstice Mojolicious
Tripletail Konstrukt Reaction Jifty Cyclone3 WebGUI
OpenInteract Squatting Dancer CGI::Application
Nanoa Ark Angelos Noe Schenker Tatsumaki Amon
Apache2::WebApp Web::Simple Apache2::REST
SweetPea Hydrant

7. Most of them run on
mod_perl and CGI

8. Some run on FastCGI

9. Some run standalone

10. Very few supports
non-blocking

11. Because:

12. No common server
environment layers

13. CGI.pm

14. Runs “fine” on:
CGI, FastCGI, mod_perl (1 & 2)
Standalone (with HTTP::Server::Simple)

15. CGI.pm = LCD
It’s also Perl core

16. :-(

17. Catalyst
The most popular framework as of today

18. Catalyst::Engine::*
Server abstractions.
Well supported Apache, FCGI and Standalone
No CGI.pm

19. CGI.pm
Jifty, CGI::Application, Spoon
mod_perl centric
Mason, Sledge, PageKit, WebGUI
Adapters
Catalyst, Maypole, Squatting

20. Problems:
Duplicated efforts
No fair performance evaluations

21. Question:
Can we share?

22. Attempt:
HTTP::Engine

23. HTTP::Engine
Lots of adapters (FCGI, Apache2, POE)
Clean Request/Response API
Written by Yappo, tokuhirom and others

24. Problems

25. Mo[ou]se everywhere
Moose is non-realistic in CGI environment
Mouse is lovely but has its own problems :p

26. Monolithic
All implementations share HTTP::Engine roles
and builders, which is sometimes hard to adapt
and has less place for optimizations.

27. APIs everywhere
Most frameworks have their request/response API
Sometimes there are gaps.
Annoying to write bridges and wrappers

28. Solution

29. Steal great stuff
from Python/Ruby

30. WSGI (Python)
Rack

31. WSGI (PEP-333)
mod_wsgi, Paste, AppEngine
Django, CherryPy, Pylons

33. Rack
Passenger, thin, Unicorn, Mongrel, Heroku
Rails, Merb, Sinatra

35. WSGI/Rack
Completely separate interface
from the actual implementation

36. Approach
Split HTTP::Engine
into three parts

37. Interface
Servers
Utils & Middleware

38. PSGI (interface)
HTTP::Server::PSGI etc. (servers)
Plack (utils & middleware)

39. PSGI
Perl Web Server Gateway Interface

40. Interface

41. WARNING
You DON’T need to care about these
interface details unless you are
framework or middleware developers
(But i guess many of you are ...)

42. # WSGI
def hello(environ, start_response):
start_response(“200 OK”, [
(‘Content-Type’, ‘text/plain’)
])
return [“Hello World”]

43. # Rack
class Hello
def call(env)
return [
200,
{ “Content-Type” => ”text/plain” },
[“Hello World”]
]
end
end

44. # PSGI
my $app = sub {
my $env = shift;
return [
200,
[ ‘Content-Type’, ‘text/plain’ ],
[ ‘Hello World’ ],
];
};

45. PSGI application
code reference
$app = sub {...};

46. my $app = sub {
my $env = shift;
return [ $status, $header, $body ];
};

47. environment hash
$env: CGI-like env variables
+ psgi.input, psgi.errors etc.

48. my $app = sub {
my $env = shift;
return [ $status, $header, $body ];
};

49. Response
array ref with three elements
status code, headers (array ref)
and body (IO-like or array ref)

50. my $app = sub {
my $env = shift;
return [ $status, $header, $body ];
};

51. $body
IO::Handle-like
getline() and close()

52. IO::Handle::Util
Easily turns perl code ref into a IO::Handle

53. Streaming interface

54. my $app = sub {
my $env = shift;
return sub {
my $respond = shift;
# You could do some event loop
# to delay response (e.g. Comet)
$respond->([ $status, $header, $body ]);
};
};

55. my $app = sub {
my $env = shift;
return sub {
my $respond = shift;
my $w = $respond->([ $status, $header ]);
$w->write($body);
$w->write($body);
...
$w->close;
};
};

56. Streaming Interface
Originally designed for non-blocking servers
Now available for most servers incl. CGI, Apache

57. Catalyst CGI::App Jifty Tatsumaki
Plack::Middleware
PSGI
Plack::Handler::* (CGI, FCGI, Apache)
Apache lighttpd HTTP::Server::PSGI mod_psgi Perlbal

58. PSGI adaptation

59. Maypole Mason Mojo Sledge Catalyst Spoon PageKit
AxKit Egg Gantry Continuity Solstice Mojolicious
Tripletail Konstrukt Reaction Jifty Cyclone3 WebGUI
OpenInteract Squatting Dancer CGI::Application
Nanoa Ark Angelos Noe Schenker Tatsumaki Amon
Apache2::WebApp Web::Simple Apache2::REST
SweetPea Hydrant

60. Maypole Mason Mojo Sledge Catalyst Spoon PageKit
AxKit Egg Gantry Continuity Solstice Mojolicious
Tripletail Konstrukt Reaction Jifty Cyclone3 WebGUI
OpenInteract Squatting Dancer CGI::Application
Nanoa Ark Angelos Noe Schenker Tatsumaki Amon
Apache2::WebApp Web::Simple Apache2::REST
SweetPea Hydrant

61. Applications
MT::App, WebGUI

62. Plack
“PSGI toolkit”

63. HTTP::Server::PSGI
Reference PSGI web server
bundled in Plack

64. Very fast
3000 QPS on standalone
15000 QPS with prefork :)

65. Plack::Handler
Connects PSGI apps to Web servers
CGI, FastCGI, Apache, Standalone

66. Utilities

67. Plackup
Run PSGI app instantly from CLI
(inspired by rackup)

68. Plack::Runner
plackup backend
Use this to make CLI for your web app

69. Middleware

71. my $app = sub {
my $env = shift;
return [ $status, $header, $body ];
};
my $mw = sub {
my $env = shift;
# do something with $env
my $res = $app->($env);
# do something with $res;
return $res;
};

72. Middleware
Debug, Session, Runtime, Static, AccessLog,
ConditionalGET, ErrorDocument, StackTrace,
Auth::Basic, Auth::Digest, ReverseProxy, Refresh etc.

73. Plack::Middleware
reusable and extensible
Middleware framework
Plack::Builder DSL in .psgi

74. my $app = sub {
return [ $status, $header, $body ];
};
use Plack::Builder;
builder {
enable “Static”, root => “/htdocs”,
path => qr!^/static/!;
enable “Deflater”; # gzip/deflate
$app;
}

75. plackup compatible
plackup -e ‘enable “Foo”;’ app.psgi

76. Plack::App::URLMap
Multiplex multiple apps
Integrated with Builder DSL

77. use CatApp;
use CGIApp;
my $c1 = sub { CatApp->run };
my $c2 = sub { CGIApp->run_psgi };
use Plack::Builder;
builder {
mount “/cat” => $c1;
mount “/cgi-app” => builder {
enable “StackTrace”;
$c2;
};
}

78. CGI::PSGI
Easy migration from CGI.pm

79. CGI::Emulate::PSGI
CGI::Compile
Easiest migration from CGI scripts (like Registry)

80. Plack::Request
like libapreq (Apache::Request)
wrapper APIs for middleware developers

81. Plack::Test
Unified interface to write tests
with Mock HTTP and Live HTTP

82. use Plack::Test;
use HTTP::Request::Common;
my $app = sub {
my $env = shift;
return [ $status, $header, $body ];
};
test_psgi app => $app, client => sub {
my $cb = shift;
my $req = GET “http://localhost/foo”;
my $res = $cb->($req);
# test $res;
};

83. use Plack::Test;
use HTTP::Request::Common;
$Plack::Test::Impl = “Server”;
my $app = sub {
my $env = shift;
return [ $status, $header, $body ];
};
test_psgi app => $app, client => sub {
my $cb = shift;
my $req = GET “http://localhost/foo”;
my $res = $cb->($req);
# test $res;
};

84. Test::WWW::Mechanize::PSGI
acme++

85. Other PSGI Servers

86. Non-blocking servers
psgi.nonblocking = true
AnyEvent, Coro, POE, Danga::Socket

87. Tatsumaki
Non-blocking Web App framework
Comet, Server push, async HTTP client
http://github.com/miyagawa/Tatsumaki

88. Nomo
Unixy PSGI web servers with supervisors support
http://github.com/miyagawa/Nomo

89. Re’em
Unicorn in Moose + FCGI::Manager
http://github.com/perigrin/re-em

90. nginx embedded perl
http://github.com/yappo/nginx-psgi-patchs

91. mod_psgi
http://github.com/spiritloose/mod_psgi

92. evpsgi
http://github.com/sekimura/evpsgi

93. Perlbal plugin
http://github.com/miyagawa/Perlbal-Plugin-PSGI

94. Catalyst CGI::App Jifty Tatsumaki
Plack::Middleware
PSGI
Plack::Handler::* (CGI, FCGI, Apache)
Apache lighttpd HTTP::Server::PSGI mod_psgi Perlbal

95. DEMO

96. Recent Updates

97. Common Confusions

98. “Is Plack a (new)
framework?”

99. No.
Plack is intended to be used by developers for
framework, web servers and middleware.

100. “But what is this
Plack::Request then?”

101. Ugh.
Plack::Request can be used as a micro framework.
But our plan is to rename the existing one.

102. “Is Plack a web server?”

103. Not anymore.
Decided to give web servers ::PSGI name such as:
HTTP::Server::PSGI, PoCo::Server::PSGI,
AnyEvent::HTTPD::PSGI, etc.

104. “Implements PSGI
= use Plack?”

105. Yeah, but not
necessarily.

106. Future

107. PSGI 1.1

108. psgi.streaming
becomes SHOULD (from MAY)
Will be BufferedStreaming middleware

109. psgi.input
read callback (for WebSockets)

110. psgi.logger
Optional: Log::Dispatch-ish logger object
useful for Debug and FirePHP integration

111. psgix.session
Optional: Session as a hash ref
(API is in Piglet)

112. Plack 1.0

113. HTTP::Server::PSGI
(partial) HTTP/1.1 support
pull prefork out of core

114. refactoring loaders
Restarter, Shotgun, gateway.cgi
Plack::Handler renames

115. Merge Plack::Request
Becomes a library for middleware writers
Make it work better when created multiple times

116. Summary
• PSGI is an interface, Plack is the code.
• We have many (pretty fast) PSGI servers.
• We have adapters and tools for most web
frameworks.
• Use it!

117. http://github.com/miyagawa/Plack
http://plackperl.org/
http://advent.plackperl.org/
irc://irc.perl.org/#plack

118. BTW

122. We can fix this.

123. 1) Help me SEO
<a href=”http://plackperl.org/”>
(put “Perl” and “Web” here)</a>

124. 2) More insanely:

125. % ls -l perlwebserver-0.3/lib/PerlWebServer/Module/
total 208
-rw-r--r-- 1 miyagawa staff 6029 Dec 15 2000 mod_cgi.pm
-rw-r--r-- 1 miyagawa staff 71770 Dec 15 2000 mod_homer.pm
-rw-r--r-- 1 miyagawa staff 5337 Jan 15 15:29 mod_psgi.pm
-rw-r--r-- 1 miyagawa staff 7394 Dec 15 2000 mod_ssi.pm

126. httpi: I gave up.
There is tools/phproxy which does similar things.

127. Questions?