Plack::App::URLMap(3) Map multiple apps in different paths

SYNOPSIS


use Plack::App::URLMap;
my $app1 = sub { ... };
my $app2 = sub { ... };
my $app3 = sub { ... };
my $urlmap = Plack::App::URLMap->new;
$urlmap->map("/" => $app1);
$urlmap->map("/foo" => $app2);
$urlmap->map("http://bar.example.com/" => $app3);
my $app = $urlmap->to_app;

DESCRIPTION

Plack::App::URLMap is a PSGI application that can dispatch multiple applications based on URL path and host names (a.k.a ``virtual hosting'') and takes care of rewriting "SCRIPT_NAME" and "PATH_INFO" (See ``HOW THIS WORKS'' for details). This module is inspired by Ruby's Rack::URLMap.

METHODS

map
  $urlmap->map("/foo" => $app);
  $urlmap->map("http://bar.example.com/" => $another_app);

Maps URL path or an absolute URL to a PSGI application. The match order is sorted by host name length and then path length (longest strings first).

URL paths need to match from the beginning and should match completely until the path separator (or the end of the path). For example, if you register the path "/foo", it will match with the request "/foo", "/foo/" or "/foo/bar" but it won't match with "/foox".

Mapping URLs with host names is also possible, and in that case the URL mapping works like a virtual host.

Mappings will nest. If $app is already mapped to "/baz" it will match a request for "/foo/baz" but not "/foo". See ``HOW THIS WORKS'' for more details.

mount
Alias for "map".
to_app
  my $handler = $urlmap->to_app;

Returns the PSGI application code reference. Note that the Plack::App::URLMap object is callable (by overloading the code dereference), so returning the object itself as a PSGI application should also work.

PERFORMANCE

If you "map" (or "mount" with Plack::Builder) N applications, Plack::App::URLMap will need to at most iterate through N paths to match incoming requests.

It is a good idea to use "map" only for a known, limited amount of applications, since mounting hundreds of applications could affect runtime request performance.

DEBUGGING

You can set the environment variable "PLACK_URLMAP_DEBUG" to see how this application matches with the incoming request host names and paths.

HOW THIS WORKS

This application works by fixing "SCRIPT_NAME" and "PATH_INFO" before dispatching the incoming request to the relocated applications.

Say you have a Wiki application that takes "/index" and "/page/*" and makes a PSGI application $wiki_app out of it, using one of supported web frameworks, you can put the whole application under "/wiki" by: 

  # MyWikiApp looks at PATH_INFO and handles /index and /page/*
  my $wiki_app = sub { MyWikiApp->run(@_) };
  
  use Plack::App::URLMap;
  my $app = Plack::App::URLMap->new;
  $app->mount("/wiki" => $wiki_app);

When a request comes in with "PATH_INFO" set to "/wiki/page/foo", the URLMap application $app strips the "/wiki" part from "PATH_INFO" and appends that to "SCRIPT_NAME".

That way, if the $app is mounted under the root (i.e. "SCRIPT_NAME" is "") with standalone web servers like Starman, "SCRIPT_NAME" is now locally set to "/wiki" and "PATH_INFO" is changed to "/page/foo" when $wiki_app gets called.

AUTHOR

Tatsuhiko Miyagawa

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