NAME

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

VERSION

version 1.3301

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 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",
            )
        )
    )
}