Dancer::Deployment(3)

NAME
Dancer::Deployment - common ways to put your Dancer app into use

VERSION
version 1.3521

DESCRIPTION
Dancer has been designed to be flexible, and this flexibility extends to your choices when deploying your Dancer app.

  Running as a cgi-script (or fast-cgi) under Apache
In providing ultimate flexibility in terms of deployment, your Dancer app can be run as a simple cgi-script out-of-the-box with no additional web server configuration needed. Your web server should recognize .cgi files and be able to serve Perl scripts. The Perl module Plack::Runner is required.

Start by adding the following to your apache configuration (httpd.conf or sites-available/*site*):

    <VirtualHost *:80>
        ServerName www.example.com

        # /srv/www.example.com is the root of your
        # dancer application
        DocumentRoot /srv/www.example.com/public

        ServerAdmin you@example.com

        <Directory "/srv/www.example.com/public">
           AllowOverride None
           Options +ExecCGI -MultiViews +SymLinksIfOwnerMatch
           Order allow,deny
           Allow from all
           AddHandler cgi-script .cgi
        </Directory>

        ScriptAlias / /srv/www.example.com/public/dispatch.cgi/

        ErrorLog  /var/log/apache2/www.example.com-error.log
        CustomLog /var/log/apache2/www.example.com-access_log common
    </VirtualHost>

Now you can access your dancer application URLs as if you were using the embedded web server.

    http://localhost/

This option is a no-brainer, easy to setup, low maintenance but serves requests slower than all other options.

You can use the same technique to deploy with FastCGI, by just changing the lines:

    AddHandler cgi-script .cgi

    ...

    ScriptAlias / /srv/www.example.com/public/dispatch.cgi

To:

    AddHandler fastcgi-script .fcgi

    ...

    ScriptAlias / /srv/www.example.com/public/dispatch.fcgi

  Running stand-alone
At the simplest, your Dancer app can run standalone, operating as its own webserver using HTTP::Server::Simple::PSGI.

Simply fire up your app:

    $ perl bin/app.pl
    >> Listening on 0.0.0.0:3000
    == Entering the dance floor ...

Point your browser at it, and away you go!

This option can be useful for small personal web apps or internal apps, but if you want to make your app available to the world, it probably won't suit you.

Running on Perl webservers with plackup

A number of Perl web servers supporting PSGI are available on cpan:

Starman
    "Starman" is a high performance web server, with support for preforking, signals and more.

Twiggy
    "Twiggy" is an "AnyEvent" web server, it's light and fast.

Corona
    "Corona" is a "Coro" based web server.

    WARNING: "Dancer"'s use of global variables and "Coro"'s threaded behaviors can cause some unexpected behaviors. See this GitHub issue <https://github.com/PerlDancer/Dancer/issues/929> for more details. Unless you have really, really strongly compelling reasons to use Corona, consider using "Twiggy" or "Starman" instead.

To start your application, just run plackup (see Plack and specific servers above for all available options):

   $ plackup bin/app.pl
   $ plackup -E deployment -s Starman --workers=10 -p 5001 -a bin/app.pl

As you can see, the scaffolded Perl script for your app can be used as a PSGI startup file.

Enabling content compression

Content compression (gzip, deflate) can be easily enabled via a Plack middleware (see Plack#Plack::Middleware): Plack::Middleware::Deflater. It's a middleware to encode the response body in gzip or deflate, based on Accept-Encoding HTTP request header.

Enable it as you would enable any Plack middleware. First you need to install Plack::Middleware::Deflater, then in the configuration file (usually environments/development.yml), add these lines:

  plack_middlewares:
    -
      - Plack::Middleware::Deflater
      - ...

These lines tell Dancer to add Plack::Middleware::Deflater to the list of middlewares to pass to Plack::Builder, when wrapping the Dancer app. The syntax is :

•   as key: the name of the Plack middleware to use

•   as value: the options to pass it as a list. In our case, there is no option to specify to Plack::Middleware::Deflater, so we use an empty YAML list.

To test if content compression works, trace the HTTP request and response before and after enabling this middleware. Among other things, you should notice that the response is gzip or deflate encoded, and contains a header "Content-Encoding" set to "gzip" or "deflate"

Hosting on DotCloud

The simplest way to achieve this is to push your main application directory to dotcloud with your "bin/app.pl" file copied to (or symlinked from) "app.psgi".

Beware that the dotcloud service enforces one environment only, named "deployment". So instead of having "environments/development.yml" or "environments/production.yml" you must have a file named "environments/deployment.yml".

Also make sure that your "Makefile.PL" (or other dependency mechanism) includes both Dancer and Plack::Request.

The default in-memory session handler won't work, and instead you should switch to something persistent. Edit "config.yml" to change "session: 'Simple'" to (for example) "session: 'YAML'".

In case you have issues with Template::Toolkit on Dotcloud

If you use the Template::Toolkit and its "INCLUDE" or "PROCESS" directives, you might need to add the search path of your view files to the config. This is probably going to be something like "INCLUDE_PATH: '/home/dotcloud/current/views'" in "config.yml".

An alternative implementation is to use a variation of the above Plack::Builder template:

 use Plack::Builder;
 use Dancer ':syntax';
 use Dancer::Handler;
 use lib 'lib';

 my $app1 = sub {
     setting appdir => '/home/dotcloud/current';
     load_app "My::App";
     Dancer::App->set_running_app("My::App");
     my $env = shift;
     Dancer::Handler->init_request_headers($env);
     my $req = Dancer::Request->new(env => $env);
     Dancer->dance($req);
 };

 builder {
     mount "/app1" => $app1;
 };

This also supports hosting multiple apps, but you probably also need to specify the specific Environment configuration to use in your application.

When mounting under a path on dotcloud, as in the above example, always create links using the uri_for() method for Dancer routes, and a "uri_base" variable for static content as shown in Dancer::Cookbook. This means whatever base path your app is mounted under, links and form submissions will continue to work.

Creating a service

You can turn your app into proper service running in background using one of the following examples:

Using Ubic

Ubic is a polymorphic service manager. You can use it to start and stop any services, automatically start them on reboots or daemon failures, and implement custom status checks.

A basic PSGI service description (usually in /etc/ubic/service/application):

    use parent qw(Ubic::Service::Plack);

    __PACKAGE__->new(
        server => 'Starman',
        app => '/path/to/your/application/app.pl',
        port => 5000,
        user => 'www-data',
    );

Run "ubic start application" to start the service.

Using daemontools

daemontools is a collection of tools for managing UNIX services. You can use it to easily start/restart/stop services.

A basic script to start an application: (in /service/application/run)

    #!/bin/sh

    # if your application is not installed in @INC path:
    export PERL5LIB='/path/to/your/application/lib'

    exec 2>&1 \
    /usr/local/bin/plackup -s Starman -a /path/to/your/application/app.pl -p 5000

Running stand-alone behind a proxy / load balancer

Another option would be to run your app stand-alone as described above, but then use a proxy or load balancer to accept incoming requests (on the standard port 80, say) and feed them to your Dancer app.

This could be achieved using various software; examples would include:

Using Apache's mod_proxy

You could set up a VirtualHost for your web app, and proxy all requests through to it:

    <VirtualHost mywebapp.example.com:80>
    ProxyPass / http://localhost:3000/
    ProxyPassReverse / http://localhost:3000/
    </VirtualHost>

Or, if you want your webapp to share an existing VirtualHost, you could have it under a specified dir:

    ProxyPass /mywebapp/ http://localhost:3000/
    <Location /mywebapp/>
        RequestHeader set Request-Base /mywebapp
    </Location>

HTTP header "Request-Base" is taken into account by Dancer, only when "behind_proxy" setting is set to true.

It is important for you to note that the Apache2 modules mod_headers, mod_proxy and mod_proxy_http must be enabled.

    a2enmod headers
    a2enmod proxy
    a2enmod proxy_http

Note that Apache does not pass protocol information when proxying, so if needed then you will need to set it manually in your Apache config:

    RequestHeader set X_FORWARDED_PROTO "https"

It is also important to set permissions for proxying for security purposes, below is an example.

    <Proxy *>
      Order allow,deny
      Allow from all
    </Proxy>

Using perlbal

"Perlbal" is a single-threaded event-based server written in Perl supporting HTTP load balancing, web serving, and a mix of the two, available from <http://www.danga.com/perlbal/>

It processes hundreds of millions of requests a day just for LiveJournal, Vox and TypePad and dozens of other "Web 2.0" applications.

It can also provide a management interface to let you see various information on requests handled etc.

It could easily be used to handle requests for your Dancer apps, too.

It can be easily installed from CPAN:

    perl -MCPAN -e 'install Perlbal'

Once installed, you'll need to write a configuration file. See the examples provided with perlbal, but you'll probably want something like:

    CREATE POOL my_dancers
    POOL my_dancers ADD 10.0.0.10:3030
    POOL my_dancers ADD 10.0.0.11:3030
    POOL my_dancers ADD 10.0.0.12:3030
    POOL my_dancers ADD 10.0.0.13:3030

    CREATE SERVICE my_webapp
    SET listen          = 0.0.0.0:80
    SET role            = reverse_proxy
    SET pool            = my_dancers
    SET persist_client  = on
    SET persist_backend = on
    SET verify_backend  = on
    ENABLE my_webapp

Using balance

"balance" is a simple load-balancer from Inlab Software, available from <http://www.inlab.de/balance.html>.

It could be used simply to hand requests to a standalone Dancer app. You could even run several instances of your Dancer app, on the same machine or on several machines, and use a machine running balance to distribute the requests between them, for some serious heavy traffic handling!

To listen on port 80, and send requests to a Dancer app on port 3000:

    balance http localhost:3000

To listen on a specified IP only on port 80, and distribute requests between multiple Dancer apps on multiple other machines:

    balance -b 10.0.0.1 80 10.0.0.2:3000 10.0.0.3:3000 10.0.0.4:3000

Using Lighttpd

You can use Lighttp's mod_proxy:

    $HTTP["url"] =~ "/application" {
        proxy.server = (
            "/" => (
                "application" => ( "host" => "127.0.0.1", "port" => 3000 )
            )
        )
    }

This configuration will proxy all request to the /application path to the path / on localhost:3000.

Using Nginx

with Nginx:

    upstream backendurl {
        server unix:THE_PATH_OF_YOUR_PLACKUP_SOCKET_HERE.sock;
    }

    server {
      listen       80;
      server_name YOUR_HOST_HERE;

      access_log /var/log/YOUR_ACCESS_LOG_HERE.log;
      error_log  /var/log/YOUR_ERROR_LOG_HERE.log info;

      root YOUR_ROOT_PROJECT/public;
      location / {
        try_files $uri @proxy;
        access_log off;
        expires max;
      }

      location @proxy {
            proxy_set_header Host $http_host;
            proxy_set_header X-Forwarded-Host $host;
            proxy_set_header X-Real-IP $remote_addr;
            proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
            proxy_set_header X-Forwarded-Proto $scheme;
            proxy_pass       http://backendurl;
      }

    }

You will need plackup to start a worker listening on a socket :

    cd YOUR_PROJECT_PATH
    sudo -u www plackup -E production -s Starman --workers=2 -l THE_PATH_OF_YOUR_PLACKUP_SOCKET_HERE.sock -a bin/app.pl

A good way to start this is to use "daemontools" and place this line with all environments variables in the "run" file.

Using HAProxy

"HAProxy" is a reliable high-performance TCP/HTTP load balancer written in C available from <http://haproxy.1wt.eu/>.

Suppose we want to run an application at "app.example.com:80" and would to use two backends listen on hosts "app-be1.example.com:3000" and "app-be2.example.com:3000".

Here is HAProxy configuration file (haproxy.conf):

    global
        nbproc  1
        maxconn 4096
        user    nobody
        group   nobody
        # haproxy logs will be collected by syslog
        # syslog: unix socket path or tcp pair (ipaddress:port)
        log     /var/run/log local0
        daemon
        # enable compression (haproxy v1.5-dev13 and above required)
        tune.comp.maxlevel  5

    defaults
        log     global
        option  httpclose
        option  httplog
        option  dontlognull
        option  forwardfor
        option  abortonclose
        mode    http
        balance roundrobin
        retries 3
        timeout connect         5s
        timeout server          30s
        timeout client          30s
        timeout http-keep-alive 200m
        # enable compression (haproxy v1.5-dev13 and above required)
        compression algo gzip
        compression type text/html application/javascript text/css application/x-javascript text/javascript

    # application frontend (available at http://app.example.com)
    frontend app.example.com
        bind                  :80
        # modify request headers
        reqadd                X-Forwarded-Proto:\ http
        reqadd                X-Forwarded-Port:\ 80
        # modify response headers
        rspdel                ^Server:.*
        rspdel                ^X-Powered-By:.*
        rspadd                Server:\ Dethklok\ (Unix/0.2.3)
        rate-limit sessions   1024
        acl is-haproxy-stats  path_beg /stats
        # uncomment if you'd like to get haproxy usage statistics
        # use_backend haproxy   if is-haproxy-stats
        default_backend       dynamic

    # haproxy statistics (available at http://app.example.com/stats)
    backend haproxy
        stats uri             /stats
        stats refresh         180s
        stats realm           app.example.com\ haproxy\ statistics
        # change credentials
        stats auth            admin1:password1
        stats auth            admin2:password2
        stats hide-version
        stats show-legends

    # application backends
    backend dynamic
        # change path_info to check and value of the Host header sent to application server
        option httpchk HEAD / HTTP/1.1\r\nHost:\ app.example.com
        server app1 app-be1.example.com:3000 check inter 30s
        server app2 app-be2.example.com:3000 check inter 30s

We will need to start the workers on each backend of our application. This can be done by starman utility:

    # on app-be1.example.com
    $ starman --workers=2 --listen :3000 /path/to/app.pl
    # on app-be2.example.com
    $ starman --workers=2 --listen :3000 /path/to/app.pl

Then start the haproxy itself:

    # check the configuration..
    $ sudo haproxy -c -f haproxy.conf
    # now really start it..
    $ sudo haproxy -f haproxy.conf

Plackup Chef Cookbook

A psgi chef cookbook supporting Dancer (as well as Catalyst) written by Alexey Melezhik is available at <http://community.opscode.com/cookbooks/psgi>.

  Running from Apache
You can run your Dancer app from Apache using the following examples:

Running from Apache with Plack

You can run your app from Apache using PSGI (Plack), with a config like the following:

    <VirtualHost myapp.example.com>
        ServerName www.myapp.example.com
        ServerAlias myapp.example.com
        DocumentRoot /websites/myapp.example.com

        <Directory /websites/myapp.example.com>
            AllowOverride None
            Order allow,deny
            Allow from all
        </Directory>

        <Location />
            SetHandler perl-script
            PerlResponseHandler Plack::Handler::Apache2
            PerlSetVar psgi_app /websites/myapp.example.com/app.pl
        </Location>

        ErrorLog  /websites/myapp.example.com/logs/error_log
        CustomLog /websites/myapp.example.com/logs/access_log common
    </VirtualHost>

To set the environment you want to use for your application (production or development), you can set it this way:

    <VirtualHost>
        ...
        SetEnv DANCER_ENVIRONMENT "production"
        ...
    </VirtualHost>

NOTE: Only a single Dancer application can be deployed using the "Plack::Handler::Apache2" method. Multiple Dancer applications will not work properly (The routes will be mixed-up between the applications).

It's recommended to start each app with "plackup" using your favorite server (Starman, for example) and then put a web server (Apache, Nginx, Perlbal, etc.) as a frontend server for both apps using reverse proxy (HTTP based, no fastcgi).

Running from Apache under appdir

If you want to deploy multiple applications under the same VirtualHost, using one application per directory for example, you can do the following.

This example uses the FastCGI dispatcher that comes with Dancer, but you should be able to adapt this to use any other way of deployment described in this guide. The only purpose of this example is to show how to deploy multiple applications under the same base directory/virtualhost.

    <VirtualHost *:80>
        ServerName localhost
        DocumentRoot "/path/to/rootdir"
        RewriteEngine On
        RewriteCond %{REQUEST_FILENAME} !-f

        <Directory "/path/to/rootdir">
            AllowOverride None
            Options +ExecCGI -MultiViews +SymLinksIfOwnerMatch
            Order allow,deny
            Allow from all
            AddHandler fastcgi-script .fcgi
        </Directory>

        RewriteRule /App1(.*)$ /App1/public/dispatch.fcgi$1 [QSA,L]
        RewriteRule /App2(.*)$ /App2/public/dispatch.fcgi$1 [QSA,L]
        ...
        RewriteRule /AppN(.*)$ /AppN/public/dispatch.fcgi$1 [QSA,L]
    </VirtualHost>

Of course, if your Apache configuration allows that, you can put the RewriteRules in a .htaccess file directly within the application's directory, which lets you add a new application without changing the Apache configuration.

  Running on lighttpd (CGI)
To run as a CGI app on lighttpd, just create a soft link to the dispatch.cgi script (created when you run dancer -a MyApp) inside your system's cgi-bin folder. Make sure mod_cgi is enabled.

    ln -s /path/to/MyApp/public/dispatch.cgi /usr/lib/cgi-bin/mycoolapp.cgi

  Running on lighttpd (FastCGI)
Make sure mod_fcgi is enabled. You also must have FCGI installed.

This example configuration uses TCP/IP:

    $HTTP["url"] == "^/app" {
        fastcgi.server += (
            "/app" => (
                "" => (
                    "host" => "127.0.0.1",
                    "port" => "5000",
                    "check-local" => "disable",
                )
            )
        )
    }

Launch your application:

    plackup -s FCGI --port 5000 bin/app.pl

This example configuration uses a socket:

    $HTTP["url"] =~ "^/app" {
        fastcgi.server += (
            "/app" => (
                "" => (
                    "socket" => "/tmp/fcgi.sock",
                    "check-local" => "disable",
                )
            )
        )
    }

Launch your application:

    plackup -s FCGI --listen /tmp/fcgi.sock bin/app.pl

AUTHOR
Dancer Core Developers

COPYRIGHT AND LICENSE
This software is copyright (c) 2010 by Alexis Sukrieh.

This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself.