Fetching contributors…
Cannot retrieve contributors at this time
186 lines (132 sloc) 6.15 KB
Plack - Perl Superglue for Web frameworks and Web Servers (PSGI toolkit)
Plack is a set of tools for using the PSGI stack. It contains middleware
components, a reference server and utilities for Web application
frameworks. Plack is like Ruby's Rack or Python's Paste for WSGI.
See PSGI for the PSGI specification and PSGI::FAQ to know what PSGI and
Plack are and why we need them.
Plack::Handler and its subclasses contains adapters for web servers. We
have adapters for the built-in standalone web server HTTP::Server::PSGI,
CGI, FCGI, Apache1, Apache2, Net::FastCGI and HTTP::Server::Simple
included in the core Plack distribution.
There are also many HTTP server implementations on CPAN that has Plack
See Plack::Handler how to write your own adapters.
Plack::Loader is a loader to load one of Plack::Handler adapters and run
PSGI application code reference with it.
Plack::Util contains a lot of utility functions for server implementors
as well as middleware authors.
.psgi files
PSGI application is a code reference but it's not easy to pass code
reference in the command line or configuration files, so Plack uses a
convention that you need a file named "app.psgi" or alike, which would
be loaded (via perl's core function "do") to return the PSGI application
code reference.
# Hello.psgi
my $app = sub {
my $env = shift;
# ...
return [ $status, $headers, $body ];
If you use a web framework, chances are that they provide a helper
utility to automatically generate these ".psgi" files for you, such as:
# MyApp.psgi
use MyApp;
my $app = sub { MyApp->run_psgi(@_) };
It's important that the return value of ".psgi" file is the code
reference. See "eg/dot-psgi" directory for more examples of ".psgi"
plackup, Plack::Runner
plackup is a command line launcher to run PSGI applications from command
line using Plack::Loader to load PSGI backends. It can be used to run
standalone servers and FastCGI daemon processes. Other server backends
like Apache2 needs a separate configuration but ".psgi" application file
can still be the same.
If you want to write your own frontend that replaces, or adds
functionalities to plackup, take a look at Plack::Runner module.
PSGI middleware is a PSGI application that wraps existent PSGI
application and plays both side of application and servers. From the
servers the wrapped code reference still looks like and behaves exactly
the same as PSGI applications.
Plack::Middleware gives you an easy way to wrap PSGI applications with a
clean API, and compatibility with Plack::Builder DSL.
Plack::Builder gives you a DSL that you can enable Middleware in ".psgi"
files to wrap existent PSGI applications.
Plack::Request, Plack::Response
Plack::Request gives you a nice wrapper API around PSGI $env hash to get
headers, cookies and query parameters much like Apache::Request in
Plack::Response does the same to construct the response array reference.
Plack::Test is an unified interface to test your PSGI application using
standard HTTP::Request and HTTP::Response pair with simple callbacks.
Plack::Test::Suite is a test suite to test a new PSGI server backend.
Patches and Bug Fixes
Small patches and bug fixes can be either submitted via nopaste on IRC
<irc://> or the github issue tracker
<>. Forking on github
<> is another good way if you intend to
make larger fixes.
See also <> when you think this
document is terribly outdated.
Module Namespaces
Modules added to the Plack:: sub-namespaces should be reasonably generic
components which are useful as building blocks and not just simply using
Middleware authors are free to use the Plack::Middleware:: namespace for
their middleware components. Middleware must be written in the pipeline
style such that they can chained together with other middleware
components. The Plack::Middleware:: modules in the core distribution are
good examples of such modules. It is recommended that you inherit from
Plack::Middleware for these types of modules.
Not all middleware components are wrappers, but instead are more like
endpoints in a middleware chain. These types of components should use
the Plack::App:: namespace. Again, look in the core modules to see
excellent examples of these (Plack::App::File, Plack::App::Directory,
etc.). It is recommended that you inherit from Plack::Component for
these types of modules.
DO NOT USE Plack:: namespace to build a new web application or a
framework. It's like naming your application under CGI:: namespace if
it's supposed to run on CGI and that is a really bad choice and would
confuse people badly.
Tatsuhiko Miyagawa
The following copyright notice applies to all the files provided in this
distribution, including binary files, unless explicitly noted otherwise.
Copyright 2009-2011 Tatsuhiko Miyagawa
Yuval Kogman (nothingmuch)
Tokuhiro Matsuno (tokuhirom)
Kazuhiro Osawa (Yappo)
Kazuho Oku
Florian Ragwitz (rafl)
Chia-liang Kao (clkao)
Masahiro Honma (hiratara)
Daisuke Murase (typester)
John Beppu
Matt S Trout (mst)
Shawn M Moore (Sartak)
Stevan Little
Hans Dieter Pearcey (confound)
Tomas Doran (t0m)
Mark Stosberg
Aaron Trevena
The PSGI specification upon which Plack is based.
The Plack wiki: <>
The Plack FAQ: <>
This library is free software; you can redistribute it and/or modify it
under the same terms as Perl itself.