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1 | =pod |
2 | |
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3 | =head1 NAME |
4 | |
5 | Catalyst::PSGI - How Catalyst and PSGI work together |
6 | |
7 | =head1 SYNOPSIS |
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8 | |
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9 | The L<PSGI> specification defines an interface between web servers and |
10 | Perl-based web applications and frameworks. It supports the writing of |
11 | portable applications that can be run using various methods (as a |
12 | standalone server, or using mod_perl, FastCGI, etc.). L<Plack> is a set |
13 | of middleware tools for running Perl applications compatible with the |
14 | PSGI specification. |
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15 | |
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16 | Catalyst used to contain an entire set of C<< Catalyst::Engine::XXXX >> |
17 | classes to handle various web servers and environments (e.g. CGI, |
18 | FastCGI, mod_perl) etc. |
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19 | |
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20 | This has been changed in Catalyst 5.9 so that all of that work is done |
21 | by Catalyst implementing the L<PSGI> specification, using L<Plack>'s |
22 | adaptors to implement that functionality. |
23 | |
24 | This means that we can share common code, and share fixes for specific |
25 | web servers. |
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26 | |
27 | =head1 I already have an application |
28 | |
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29 | If you already have a Catalyst application, then you should be able to |
30 | upgrade to the latest release with little or no trouble (see the notes |
31 | in L<Catalyst::Upgrading> for specifics about your web server |
32 | deployment). |
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33 | |
34 | =head1 Writing your own PSGI file. |
35 | |
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36 | =head2 What is a .psgi file? |
37 | |
38 | A C<< .psgi >> file lets you control how your application code reference |
39 | is built. Catalyst will automatically handle this for you, but it's |
40 | possible to do it manually by creating a C<myapp.psgi> file in the root |
41 | of your application. |
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42 | |
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43 | =head2 Why would I want to write my own .psgi file? |
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44 | |
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45 | Writing your own .psgi file allows you to use the alternate L<plackup> command |
46 | to start your application, and allows you to add classes and extensions |
47 | that implement L<Plack::Middleware>, such as L<Plack::Middleware::ErrorDocument> |
48 | or L<Plack::Middleware::AccessLog>. |
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49 | |
50 | The simplest C<.psgi> file for an application called C<TestApp> would be: |
51 | |
52 | use strict; |
53 | use warnings; |
54 | use TestApp; |
55 | |
56 | my $app = sub { TestApp->psgi_app(@_) }; |
57 | |
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58 | Note that Catalyst will apply a number of middleware components for you |
59 | automatically, and these B<will not> be applied if you manually create a |
60 | psgi file yourself. Details of these components can be found below. |
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61 | |
62 | Additional information about psgi files can be found at: |
63 | L<http://search.cpan.org/dist/Plack/lib/Plack.pm#.psgi_files> |
64 | |
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65 | =head2 What is in the .psgi file Catalyst generates by default? |
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66 | |
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67 | Catalyst generates an application which, if the C<< using_frontend_proxy |
68 | >> setting is on, is wrapped in L<Plack::Middleware::ReverseProxy>, and |
69 | contains some engine-specific fixes for uniform behaviour, as contained |
70 | in: |
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71 | |
72 | =over |
73 | |
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74 | =item L<Plack::Middleware::LighttpdScriptNameFix> |
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75 | |
76 | =item L<Plack::Middleware::IIS6ScriptNameFix> |
77 | |
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78 | =item nginx - local to Catalyst |
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79 | |
80 | =back |
81 | |
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82 | If you override the default by providing your own C<< .psgi >> file, |
83 | then none of these things will be done automatically for you by the PSGI |
84 | application returned when you call C<< MyApp->psgi_app >>. Thus, if you |
85 | need any of this functionality, you'll need to implement this in your |
86 | C<< .psgi >> file yourself. |
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87 | |
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88 | An apply_default_middlewares method is supplied to wrap your application |
89 | in the default middlewares if you want this behaviour and you are providing |
90 | your own .psgi file. |
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91 | |
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92 | =head1 SEE ALSO |
93 | |
94 | L<Catalyst::Upgrading>, L<Plack>, L<PSGI::FAQ>, L<PSGI>. |
95 | |
96 | =head1 AUTHORS |
97 | |
98 | Catalyst Contributors, see Catalyst.pm |
99 | |
100 | =head1 COPYRIGHT |
101 | |
102 | This library is free software. You can redistribute it and/or modify |
103 | it under the same terms as Perl itself. |
104 | |
105 | =cut |