=head1 NAME

Catalyst::Manual::Deployment::Apache::FastCGI - Deploying Catalyst with FastCGI on Apache

=head2 Setup

=head3 1. Install Apache with mod_fastcgi

mod_fastcgi for Apache is a third-party module, and can be found at
L<https://fastcgi-archives.github.io/>. It is also packaged in many distributions
(for example, libapache2-mod-fastcgi in Debian). You will also need to
install the L<FCGI> module from CPAN.

Important Note! If you experience difficulty properly rendering pages,
try disabling Apache's mod_deflate (Deflate Module), e.g. 'a2dismod deflate'.

=head2 Apache 1.x, 2.x

Apache requires the mod_fastcgi module.  The same module supports both
Apache 1 and 2.

There are three ways to run your application under FastCGI on Apache: server,
static, and dynamic.

=head3 Standalone server mode

    FastCgiExternalServer /tmp/myapp.fcgi -socket /tmp/myapp.socket
    Alias /myapp/ /tmp/myapp.fcgi/

    # Or, run at the root
    Alias / /tmp/myapp.fcgi/

    # Optionally, rewrite the path when accessed without a trailing slash
    RewriteRule ^/myapp$ myapp/ [R]


The FastCgiExternalServer directive tells Apache that when serving
/tmp/myapp to use the FastCGI application listening on the socket
/tmp/mapp.socket.  Note that /tmp/myapp.fcgi B<MUST NOT> exist --
it's a virtual file name.  With some versions of C<mod_fastcgi> or
C<mod_fcgid>, you can use any name you like, but some require that the
virtual filename end in C<.fcgi>.

It's likely that Apache is not configured to serve files in /tmp, so the
Alias directive maps the url path /myapp/ to the (virtual) file that runs the
FastCGI application. The trailing slashes are important as their use will
correctly set the PATH_INFO environment variable used by Catalyst to
determine the request path.  If you would like to be able to access your app
without a trailing slash (http://server/myapp), you can use the above
RewriteRule directive.

=head3 Static mode

The term 'static' is misleading, but in static mode Apache uses its own
FastCGI Process Manager to start the application processes.  This happens at
Apache startup time.  In this case you do not run your application's
fastcgi.pl script -- that is done by Apache. Apache then maps URIs to the
FastCGI script to run your application.

    FastCgiServer /path/to/myapp/script/myapp_fastcgi.pl -processes 3
    Alias /myapp/ /path/to/myapp/script/myapp_fastcgi.pl/

FastCgiServer tells Apache to start three processes of your application at
startup.  The Alias command maps a path to the FastCGI application. Again,
the trailing slashes are important.

=head3 Dynamic mode

In FastCGI dynamic mode, Apache will run your application on demand,
typically by requesting a file with a specific extension (e.g. .fcgi).  ISPs
often use this type of setup to provide FastCGI support to many customers.

In this mode it is often enough to place or link your *_fastcgi.pl script in
your cgi-bin directory with the extension of .fcgi.  In dynamic mode Apache
must be able to run your application as a CGI script so ExecCGI must be
enabled for the directory.

    AddHandler fastcgi-script .fcgi

The above tells Apache to run any .fcgi file as a FastCGI application.

Here is a complete example:

    <VirtualHost *:80>
        ServerName www.myapp.com
        DocumentRoot /path/to/MyApp

        # Allow CGI script to run
        <Directory /path/to/MyApp>
            Options +ExecCGI
        </Directory>

        # Tell Apache this is a FastCGI application
        <Files myapp_fastcgi.pl>
            SetHandler fastcgi-script
        </Files>
    </VirtualHost>

Then a request for /script/myapp_fastcgi.pl will run the
application.

For more information on using FastCGI under Apache, visit
L<https://fastcgi-archives.github.io/mod_fastcgi.html>

=head3 Authorization header with mod_fastcgi or mod_cgi

By default, mod_fastcgi/mod_cgi do not pass along the Authorization header,
so modules like L<Catalyst::Plugin::Authentication::Credential::HTTP> will
not work.  To enable pass-through of this header, add the following
mod_rewrite directives:

    RewriteCond %{HTTP:Authorization} ^(.+)
    RewriteRule ^(.*)$ $1 [E=HTTP_AUTHORIZATION:%1,PT]


=head4 2. Configure your application

    # Serve static content directly
    DocumentRoot  /var/www/MyApp/root
    Alias /static /var/www/MyApp/root/static

    FastCgiServer /var/www/MyApp/script/myapp_fastcgi.pl -processes 3
    Alias /myapp/ /var/www/MyApp/script/myapp_fastcgi.pl/

    # Or, run at the root
    Alias / /var/www/MyApp/script/myapp_fastcgi.pl/

The above commands will launch 3 app processes and make the app available at
/myapp/

=head3 Standalone server mode

While not as easy as the previous method, running your app as an external
server gives you much more flexibility.

First, launch your app as a standalone server listening on a socket.

    script/myapp_fastcgi.pl -l /tmp/myapp.socket -n 5 -p /tmp/myapp.pid -d

You can also listen on a TCP port if your web server is not on the same
machine.

    script/myapp_fastcgi.pl -l :8080 -n 5 -p /tmp/myapp.pid -d

You will probably want to write an init script to handle starting/stopping
of the app using the pid file.

Now, we simply configure Apache to connect to the running server.

    # 502 is a Bad Gateway error, and will occur if the backend server is down
    # This allows us to display a friendly static page that says "down for
    # maintenance"
    Alias /_errors /var/www/MyApp/root/error-pages
    ErrorDocument 502 /_errors/502.html

    FastCgiExternalServer /tmp/myapp.fcgi -socket /tmp/myapp.socket
    Alias /myapp/ /tmp/myapp.fcgi/

    # Or, run at the root
    Alias / /tmp/myapp.fcgi/

=head3 More Info

L<Catalyst::Manual::Deployment::FastCGI>.

=head1 AUTHORS

Catalyst Contributors, see Catalyst.pm

=head1 COPYRIGHT

This library is free software. You can redistribute it and/or modify it under
the same terms as Perl itself.

=cut