Plack - Perl Superglue for Web frameworks and Web Servers (PSGI toolkit)
Plack is a set of PSGI reference server implementations and helper utilities for Web application frameworks, exactly like Ruby's Rack.
Plack::Handler and its subclasses contains adapters for web servers. We have adapters for Standalone, CGI, FCGI, Apache, AnyEvent, Coro, Danga::Socket and many server environments that you can run PSGI applications on.
See Plack::Handler how to write your own adapters.
Plack::Loader is a loader to load one of Plack::Server 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 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.
See eg/dot-psgi directory for the example
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.
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::Builder gives you a DSL that you can enable Middleware in
.psgi files to wrap existent PSGI applications.
Plack::Response does the same to construct the response array reference.
Plack::Test::Suite is a test suite to test a new PSGI server backend.
Modules added to the Plack:: sub-namespaces should be reasonably generic components which are useful as building blocks and not just simply using Plack.
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 confuse people.
Copyright 2009- Tatsuhiko Miyagawa