Provided by: libdancer2-perl_0.11+dfsg-1_all 
NAME
Dancer2::Cookbook - Example-driven quick-start to the Dancer2 web framework
VERSION
version 0.11
DESCRIPTION
A quick-start guide with examples to get you up and running with the Dancer2 web
framework.
BEGINNER'S DANCE
Your first Dancer2 web app
Dancer2 has been designed to be easy to work with - it's trivial to write a simple web
app, but still has the power to work with larger projects. To start with, let's make an
incredibly simple "Hello World" example:
#!/usr/bin/perl
use Dancer2;
get '/hello/:name' => sub {
return "Why, hello there " . params->{name};
};
dance;
Yes - the above is a fully-functioning web app; running that script will launch a
webserver listening on the default port (3000); now you can make a request
$ curl http://localhost:3000/hello/Bob
Why, hello there Bob
(or the name of the machine you ran it on, if it's not your local system), and it will say
hello. The ":name" part is a named parameter within the route specification, whose value
is made available through "params" - more on that later.
Note that you don't need to use the "strict" and "warnings" pragma, they are already
loaded by Dancer2.
If you really do not want the "warnings" pragma (for example, due to an undesired warning
about use of undef values), add a "no warnings" pragma to the appropriate block in your
module or psgi file.
Starting a Dancer2 project
The first simple example is fine for trivial projects, but for anything more complex,
you'll want a more maintainable solution - enter the "dancer2" helper script, which will
build the framework of your application with a single command:
$ dancer2 -a mywebapp
+ mywebapp
+ mywebapp/bin
+ mywebapp/bin/app.pl
+ mywebapp/config.yml
+ mywebapp/environments
+ mywebapp/environments/development.yml
+ mywebapp/environments/production.yml
+ mywebapp/views
+ mywebapp/views/index.tt
+ mywebapp/views/layouts
+ mywebapp/views/layouts/main.tt
+ mywebapp/MANIFEST.SKIP
+ mywebapp/lib
mywebapp/lib/
+ mywebapp/lib/mywebapp.pm
+ mywebapp/public
+ mywebapp/public/css
+ mywebapp/public/css/style.css
+ mywebapp/public/css/error.css
+ mywebapp/public/images
+ mywebapp/public/500.html
+ mywebapp/public/404.html
+ mywebapp/public/dispatch.fcgi
+ mywebapp/public/dispatch.cgi
+ mywebapp/public/javascripts
+ mywebapp/public/javascripts/jquery.js
+ mywebapp/t
+ mywebapp/t/002_index_route.t
+ mywebapp/t/001_base.t
+ mywebapp/Makefile.PL
As you can see, it creates a directory named after the name of the app, along with a
configuration file, a views directory (where your templates and layouts will live), an
environments directory (where environment-specific settings live), a module containing the
actual guts of your application, a script to start it - or to run your web app via
Plack/PSGI - more on that later.
DANCE ROUTINES: ROUTES
Declaring routes
To control what happens when a web request is received by your webapp, you'll need to
declare "routes". A route declaration indicates which HTTP method(s) it is valid for, the
path it matches (e.g. /foo/bar), and a coderef to execute, which returns the response.
get '/hello/:name' => sub {
return "Hi there " . params->{name};
};
The above route specifies that, for GET requests to '/hello/...', the code block provided
should be executed.
Handling multiple HTTP request methods
Routes can use "any" to match all, or a specified list of HTTP methods.
The following will match any HTTP request to the path /myaction:
any '/myaction' => sub {
# code
}
The following will match GET or POST requests to /myaction:
any ['get', 'post'] => '/myaction' => sub {
# code
};
For convenience, any route which matches GET requests will also match HEAD requests.
Retrieving request parameters
The params keyword returns a hashref of request parameters; these will be parameters
supplied on the query string, within the path itself (with named placeholders), and, for
HTTTP POST requests, the content of the POST body.
Named parameters in route path declarations
As seen above, you can use ":somename" in a route's path to capture part of the path; this
will become available by calling params.
So, for a web app where you want to display information on a company, you might use
something like:
get '/company/view/:companyid' => sub {
my $company_id = params->{companyid};
# Look up the company and return appropriate page
};
Wildcard path matching and splat
You can also declare wildcards in a path, and retrieve the values they matched with the
splat keyword:
get '/*/*' => sub {
my ($action, $id) = splat;
if (my $action eq 'view') {
return display_item($id);
} elsif ($action eq 'delete') {
return delete_item($id);
} else {
status 'not_found';
return "What?";
}
};
Before filters - processed before a request
A before filter declares code which should be handled before a request is passed to the
appropriate route.
hook before => sub {
forward '/foo/oversee', { note => 'Hi there' };
};
get '/foo/*' => sub {
my ($match) = splat; # 'oversee';
params->{note}; # 'Hi there'
};
The above declares a before filter which uses "forward" to do an internal redirect to
"/foo/oversee" with an additional parameter "note".
See also the hook hook keyword.
Default route
In case you want to avoid a 404 error, or handle multiple routes in the same way and you
don't feel like configuring all of them, you can set up a default route handler.
The default route handler will handle any request that doesn't get served by any other
route.
All you need to do is set up the following route as the last route:
any qr{.*} => sub {
status 'not_found';
template 'special_404', { path => request->path };
};
Then you can set up the template as such:
You tried to reach [% path %], but it is unavailable at the moment.
Please try again or contact us at our email at <...>.
Using the auto_page feature for automatic route creation
For simple "static" pages, you can simply enable the "auto_page" config setting; this
means that you need not declare a route handler for those pages; if a request is for
"/foo/bar", Dancer2 will check for a matching view (e.g. "/foo/bar.tt" and render it with
the default layout etc if found. For full details, see the documentation for the
auto_page setting.
Why should I use the Ajax plugin
As an Ajax query is just a HTTP query, it's similar to a GET or POST route. You may ask
yourself why you may want to use the "ajax" keyword (from the Dancer2::Plugin::Ajax
plugin) instead of a simple "get".
Let's say you have a path like '/user/:user' in your application. You may want to be able
to serve this page, with a layout and HTML content. But you may also want to be able to
call this same url from a javascript query using Ajax.
So, instead of having the following code:
get '/user/:user' => sub {
if (request->is_ajax) {
# create xml, set headers to text/xml, blablabla
header('Content-Type' => 'text/xml');
header('Cache-Control' => 'no-store, no-cache, must-revalidate');
to_xml({...})
}else{
template users, {....}
}
};
you can have
get '/user/:user' => sub {
template users, {...}
}
and
ajax '/user/:user' => sub {
to_xml({...}, RootName => undef);
}
Because it's an ajax query, you know you need to return a xml content, so the content type
of the response is set for you.
Using the prefix feature to split your application
For better maintainability, you may want to separate some of your application components
to different packages. Let's say we have a simple web app with an admin section, and want
to maintain this in a different package:
package myapp;
use Dancer2;
use myapp::admin;
prefix undef;
get '/' => sub {...};
1;
package myapp::admin;
use Dancer2;
prefix '/admin';
get '/' => sub {...};
1;
The following routes will be generated for us:
- get /
- get /admin/
- head /
- head /admin/
MUSCLE MEMORY: STORING DATA
Handling sessions
It's common to want to use sessions to give your web applications state; for instance,
allowing a user to log in, creating a session, and checking that session on subsequent
requests.
To make use of sessions, you must first enable the session engine - pick the session
engine you want to use, then declare it in your config file like this:
session: Simple
The Dancer2::Session::Simple backend implements very simple in-memory session storage.
This will be fast and useful for testing, but sessions do not persist between restarts of
your app.
You can also use the Dancer2::Session::YAML backend included with Dancer2, which stores
session data on disc in YAML files (since YAML is a nice human-readable format, it makes
inspecting the contents of sessions a breeze):
session: YAML
Or, to enable session support from within your code,
set session => 'YAML';
(Controlling settings is best done from your config file, though). 'YAML' in the example
is the session backend to use; this is shorthand for Dancer2::Session::YAML. There are
other session backends you may wish to use, for instance Dancer2::Session::Memcache, but
the YAML backend is a simple and easy to use example which stores session data in a YAML
file in sessions).
You can then use the session keyword to manipulate the session:
Storing data in the session
Storing data in the session is as easy as:
session varname => 'value';
Retrieving data from the session
Retrieving data from the session is as easy as:
session('varname')
Or, alternatively,
session->read("varname")
Controlling where sessions are stored
For disc-based session back ends like Dancer2::Session::YAML, Dancer2::Session::Storable
etc, session files are written to the session dir specified by the "session_dir" setting,
which defaults to "./sessions" if not specifically set.
If you need to control where session files are created, you can do so quickly and easily
within your config file, for example:
session: YAML
engines:
session:
YAML:
session_dir: /tmp/dancer-sessions
If the directory you specify does not exist, Dancer2 will attempt to create it for you.
Destroying a session
When you're done with your session, you can destroy it:
context->destroy_session
Sessions and logging in
A common requirement is to check the user is logged in, and, if not, require them to log
in before continuing.
This can easily be handled with a before filter to check their session:
use Dancer2;
set session => "Simple";
hook before => sub {
if (!session('user') && request->dispatch_path !~ m{^/login}) {
forward '/login', { requested_path => request->dispatch_path };
}
};
get '/' => sub { return "Home Page"; };
get '/secret' => sub { return "Top Secret Stuff here"; };
get '/login' => sub {
# Display a login page; the original URL they requested is available as
# param('requested_path'), so could be put in a hidden field in the form
template 'login', { path => param('requested_path') };
};
post '/login' => sub {
# Validate the username and password they supplied
if (param('user') eq 'bob' && param('pass') eq 'letmein') {
session user => param('user');
redirect param('path') || '/';
} else {
redirect '/login?failed=1';
}
};
dance();
Here is what the corresponding "login.tt" file should look like. You should place it in a
directory called views:
<html>
<head>
<title>Session and logging in</title>
</head>
<body>
<form action='/login' method='POST'>
User Name : <input type='text' name='user'/>
Password: <input type='password' name='pass' />
<!-- Put the original path requested into a hidden
field so it's sent back in the POST and can be
used to redirect to the right page after login -->
<input type='hidden' name='path' value='[% path %]'/>
<input type='submit' value='Login' />
</form>
</body>
</html>
Of course, you'll probably want to validate your users against a database table, or maybe
via IMAP/LDAP/SSH/POP3/local system accounts via PAM etc. Authen::Simple is probably a
good starting point here!
A simple working example of handling authentication against a database table yourself
(using Dancer2::Plugin::Database which provides the "database" keyword, and
Crypt::SaltedHash to handle salted hashed passwords (well, you wouldn't store your users
passwords in the clear, would you?)) follows:
post '/login' => sub {
my $user = database->quick_select('users',
{ username => params->{user} }
);
if (!$user) {
warning "Failed login for unrecognised user " . params->{user};
redirect '/login?failed=1';
} else {
if (Crypt::SaltedHash->validate($user->{password}, params->{pass}))
{
debug "Password correct";
# Logged in successfully
session user => $user;
redirect params->{path} || '/';
} else {
debug("Login failed - password incorrect for " . params->{user});
redirect '/login?failed=1';
}
}
};
Retrieve complete hash stored in session
Get complete hash stored in session:
my $hash = session;
APPEARANCE: TEMPLATES AND LAYOUTS
Returning plain content is all well and good for examples or trivial apps, but soon you'll
want to use templates to maintain separation between your code and your content. Dancer2
makes this easy.
Your route handlers can use the template keyword to render templates.
Views
It's possible to render the action's content with a template, this is called a view. The
`appdir/views' directory is the place where views are located.
You can change this location by changing the setting 'views'.
By default, the internal template engine Dancer2::Template::Simple is used, but you may
want to upgrade to Template Toolkit <http://www.template-toolkit.org/>. If you do so, you
have to enable this engine in your settings as explained in
Dancer2::Template::TemplateToolkit and you'll also have to import the Template module in
your application code.
All views must have a '.tt' extension. This may change in the future.
In order to render a view, just call the template keyword at the end of the action by
giving the view name and the HASHREF of tokens to interpolate in the view (note that for
convenience, the request, session, params and vars are automatically accessible in the
view, named "request", "session", "params" and "vars") - for example:
hook before => sub { var time => scalar(localtime) };
get '/hello/:name' => sub {
my $name = params->{name};
template 'hello.tt', { name => $name };
};
The template "hello.tt" could contain, for example:
<p>Hi there, [% name %]!</p>
<p>You're using [% request.user_agent %]</p>
[% IF session.username %]
<p>You're logged in as [% session.username %]</p>
[% END %]
It's currently [% vars.time %]
For a full list of the tokens automatically added to your template (like "session",
"request" and "vars", refer to Dancer2::Core::Role::Template).
Layouts
A layout is a special view, located in the 'layouts' directory (inside the views
directory) which must have a token named "content". That token marks the place where to
render the action view. This lets you define a global layout for your actions, and have
each individual view contain only the specific content. This is a good thing to avoid
lots of needless duplication of HTML :)
Here is an example of a layout: "views/layouts/main.tt" :
<html>
<head>...</head>
<body>
<div id="header">
...
</div>
<div id="content">
[% content %]
</div>
</body>
</html>
You can tell your app which layout to use with "layout: name" in the config file, or
within your code:
set layout => 'main';
You can control which layout to use (or whether to use a layout at all) for a specific
request without altering the layout setting by passing an options hashref as the third
param to the template keyword:
template 'index.tt', {}, { layout => undef };
If your application is not mounted under root (/), you can use a before_template instead
of hardcoding the path to your application for your css, images and javascript:
hook before_template_render => sub {
my $tokens = shift;
$tokens->{uri_base} = request->base->path;
};
Then in your layout, modify your css inclusion as follows:
<link rel="stylesheet" href="[% uri_base %]/css/style.css" />
From now on, you can mount your application wherever you want, without any further
modification of the css inclusion
Templates and unicode
If you use Plack and have some unicode problem with your Dancer2 application, don't forget
to check if you have set your template engine to use unicode, and set the default charset
to UTF-8. So, if you are using template toolkit, your config file will look like this:
charset: UTF-8
engines:
template:
template_toolkit:
ENCODING: utf8
TT's WRAPPER directive in Dancer2
Dancer2 already provides a WRAPPER-like ability, which we call a "layout". The reason we
do not use TT's WRAPPER (which also makes us incompatible with it) is because not all
template systems support it. Actually, most don't.
However, you might want to use it, and be able to define META variables and regular
Template::Toolkit variables.
These few steps will get you there:
• Disable the layout in Dancer2
You can do this by simply commenting (or removing) the "layout" configuration in the
config file.
• Use Template Toolkit template engine
Change the configuration of the template to Template Toolkit:
# in config.yml
template: "template_toolkit"
• Tell the Template Toolkit engine who's your wrapper
# in config.yml
# ...
engines:
template:
template_toolkit:
WRAPPER: layouts/main.tt
Done! Everything will work fine out of the box, including variables and META variables.
SETTING THE STAGE: CONFIGURATION AND LOGGING
Configuration and environments
Configuring a Dancer2 application can be done in many ways. The easiest one (and maybe the
dirtiest) is to put all your settings statements at the top of your script, before calling
the dance() method.
Other ways are possible, you can define all your settings in the file "appdir/config.yml".
For this, you must have installed the YAML module, and of course, write the config file in
YAML.
That's better than the first option, but it's still not perfect as you can't switch easily
from an environment to another without rewriting the config file.
An even solution is to have one config.yml file with default global settings, like the
following:
# appdir/config.yml
logger: 'file'
layout: 'main'
And then write as many environment files as you like in "appdir/environments". That way,
the appropriate environment config file will be loaded according to the running
environment (if none is specified, it will be 'development').
Note that you can change the running environment using the "--environment" command line
switch.
Typically, you'll want to set the following values in a development config file:
# appdir/environments/development.yml
log: 'debug'
startup_info: 1
show_errors: 1
And in a production one:
# appdir/environments/production.yml
log: 'warning'
startup_info: 0
show_errors: 0
Accessing configuration information
From inside your application
A Dancer2 application can use the 'config' keyword to easily access the settings within
its config file, for instance:
get '/appname' => sub {
return "This is " . config->{appname};
};
This makes keeping your application's settings all in one place simple and easy - you
shouldn't need to worry about implementing all that yourself :)
From a separate script
You may well want to access your webapp's configuration from outside your webapp. You
could, of course, use the YAML module of your choice and load your webapps's config.yml,
but chances are that this is not convenient.
Use Dancer2 instead. Without any ado, magic or too big jumps, you can use the values from
config.yml and some additional default values:
# bin/script1.pl
use Dancer2;
print "template:".config->{template}."\n"; #simple
print "log:".config->{log}."\n"; #undef
Note that "config->{log}" should result undef error on a default scaffold since you did
not load the environment and in the default scaffold log is defined in the environment and
not in config.yml. Hence undef.
If you want to load an environment you need to tell Dancer2 where to look for it. One way
to do so, is to tell Dancer2 where the webapp lives. From there Dancer2 deduces where the
config.yml file is (typically "$webapp/config.yml").
# bin/script2.pl
use FindBin;
use Cwd qw/realpath/;
use Dancer2;
#tell the Dancer2 where the app lives
my $appdir=realpath( "$FindBin::Bin/..");
Dancer2::Config::setting('appdir',$appdir);
Dancer2::Config::load();
#getter
print "environment:".config->{environment}."\n"; #development
print "log:".config->{log}."\n"; #value from development environment
By default Dancer2 loads development environment (typically
"$webapp/environment/development.yml"). In contrast to the example before, you do have a
value from the development environment ("environment/development.yml") now. Also note that
in the above example Cwd and FindBin are used. They are likely to be already loaded by
Dancer2 anyways, so it's not a big overhead. You could just as well hand over a simple
path for the app if you like that better, e.g.:
Dancer2::Config::setting('appdir','/path/to/app/dir');
If you want to load an environment other than the default, try this:
# bin/script2.pl
use Dancer2;
#tell the Dancer2 where the app lives
Dancer2::Config::setting('appdir','/path/to/app/dir');
#which environment to load
config->{environment}='production';
Dancer2::Config::load();
#getter
print "log:".config->{log}."\n"; #has value from production environment
By the way, you not only get values, you can also set values straightforward like we do
above with "config->{environment}='production'". Of course, this value does not get
written in any file; it only lives in memory and your webapp doesn't have access to it,
but you can use it inside your script.
Logging
Configuring logging
It's possible to log messages generated by the application and by Dancer2 itself.
To start logging, select the logging engine you wish to use with the "logger" setting;
Dancer2 includes built-in log engines named "file" and "console", which log to a logfile
and to the console respectively.
To enable logging to a file, add the following to your config file:
logger: 'file'
Then you can choose which kind of messages you want to actually log:
log: 'core' # will log debug, warnings, errors,
# and messages from Dancer2 itself
log: 'debug' # will log debug, info, warning and errors
log: 'info' # will log info, warning and errors
log: 'warning' # will log warning and errors
log: 'error' # will log only errors
If you're using the "file" logging engine, a directory "appdir/logs" will be created and
will host one logfile per environment. The log message contains the time it was written,
the PID of the current process, the message and the caller information (file and line).
Logging your own messages
Just call debug, info, warning or error with your message:
debug "This is a debug message from my app.";
RESTING
Writing a REST application
With Dancer2, it's easy to write REST applications. Dancer2 provides helpers to serialize
and deserialize for the following data formats:
JSON
YAML
XML
Data::Dumper
To activate this feature, you only have to set the "serializer" setting to the format you
require, for instance in your config file:
serializer: JSON
Or right in your code:
set serializer => 'JSON';
From now, all hash ref or array ref returned by a route will be serialized to the format
you chose, and all data received from POST or PUT requests will be automatically
deserialized.
get '/hello/:name' => sub {
# this structure will be returned to the client as
# {"name":"$name"}
return {name => params->{name}};
};
It's possible to let the client choose which serializer he want to use. For this, use the
mutable serializer, and an appropriate serializer will be chosen from the Content-Type
header.
It's also possible to return a custom error, using the send_error keyword.. When you
don't use a serializer, the "send_error" function will take a string as first parameter
(the message), and an optional HTTP code. When using a serializer, the message can be a
string, an arrayref or a hashref:
get '/hello/:name' => sub {
if (...) {
send_error("you can't do that");
# or
send_error({reason => 'access denied', message => "no"});
}
};
The content of the error will be serialized using the appropriate serializer.
DANCER ON THE STAGE: DEPLOYMENT
Running stand-alone
At the simplest, your Dancer2 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.
Auto Reloading with Plack and Shotgun
To edit your files without the need to restart the webserver on each file change, simply
start your Dancer2 app using plackup and Plack::Loader::Shotgun:
$ plackup -L Shotgun bin/app.pl
HTTP::Server::PSGI: Accepting connections at http://0:5000/
Point your browser at it. Files can now be changed in your favorite editor and the browser
needs to be refreshed to see the saved changes.
Please note that this is not recommended for production for performance reasons. This is
the Dancer2 replacement solution of the old Dancer experimental "auto_reload" option.
On Windows, Shotgun loader is known to cause huge memory leaks in a fork-emulation layer.
If you are aware of this and still want to run the loader, please use the following
command:
> set PLACK_SHOTGUN_MEMORY_LEAK=1 && plackup -L Shotgun bin\app.pl
HTTP::Server::PSGI: Accepting connections at http://0:5000/
CGI and Fast-CGI
In providing ultimate flexibility in terms of deployment, your Dancer2 app can be run as a
simple cgi-script out-of-the-box. 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.
Running on Apache (CGI and FCGI)
Start by adding the following to your apache configuration ("httpd.conf" or
"sites-available/*site*"):
<VirtualHost *:80>
ServerName www.example.com
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>
RewriteEngine On
RewriteCond %{REQUEST_FILENAME} !-f
RewriteRule ^(.*)$ /dispatch.cgi$1 [QSA,L]
ErrorLog /var/log/apache2/www.example.com-error.log
CustomLog /var/log/apache2/www.example.com-access_log common
</VirtualHost>
Note that when using fast-cgi your rewrite rule should be:
RewriteRule ^(.*)$ /dispatch.fcgi$1 [QSA,L]
Here, the mod_rewrite magic for Pretty-URLs is directly put in Apache's configuration.
But if your web server supports .htaccess files, you can drop those lines in a .htaccess
file.
To check if your server supports mod_rewrite type "apache2 -l" to list modules. To enable
mod_rewrite (Debian), run "a2enmod rewrite". Place following code in a file called
.htaccess in your application's root folder:
# BEGIN dancer application htaccess
RewriteEngine On
RewriteCond %{SCRIPT_FILENAME} !-d
RewriteCond %{SCRIPT_FILENAME} !-f
RewriteRule (.*) /dispatch.cgi$1 [L]
# END dancer application htaccess
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 line:
AddHandler cgi-script .cgi
By:
AddHandler fastcgi-script .fcgi
Of course remember to update your rewrite rules, if you have set any:
RewriteRule (.*) /dispatch.fcgi$1 [L]
Running under an appdir
If you want to deploy multiple applications under the same VirtualHost, using one
application per directory for example, you can do the following.
This example uses the FastCGI dispatcher that comes with Dancer2, but you should be able
to adapt this to use any other way of deployment described in this guide. The only purpose
of this example is to show how to deploy multiple applications under the same base
directory/virtualhost.
<VirtualHost *:80>
ServerName localhost
DocumentRoot "/path/to/rootdir"
RewriteEngine On
RewriteCond %{REQUEST_FILENAME} !-f
<Directory "/path/to/rootdir">
AllowOverride None
Options +ExecCGI -MultiViews +SymLinksIfOwnerMatch
Order allow,deny
Allow from all
AddHandler fastcgi-script .fcgi
</Directory>
RewriteRule /App1(.*)$ /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
Plack middlewares
If you want to use Plack middlewares, you need to enable them using Plack::Builder as
such:
# in app.psgi or any other handler
use Dancer2;
use MyWebApp;
use Plack::Builder;
builder {
enable 'Deflater';
enable 'Session', store => 'File';
enable 'Debug', panels => [ qw<DBITrace Memory Timer> ];
dance;
};
The nice thing about this setup is that it will work seamlessly through Plack or through
the internal web server.
# load dev web server (without middlewares)
perl -Ilib app.psgi
# load plack web server (with middlewares)
plackup -I lib app.psgi
You do not need to provide different files for either server.
Path-based middlewares
If you want to setup a middleware for a specific path, you can do that using
Plack::Builder which uses Plack::App::URLMap:
# in your app.psgi or any other handler
use Dancer2;
use MyWebApp;
use Plack::Builder;
my $special_handler = sub { ... };
builder {
mount '/' => dance;
mount '/special' => $special_handler;
};
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, ...
Twiggy
"Twiggy" is an "AnyEvent" web server, it's light and fast.
Corona
"Corona" is a "Coro" based web server.
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::Middleware" in Plack): 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 handler (usually app.psgi) edit it to use
Plack::Builder, as described above:
use Dancer2;
use MyWebApp;
use Plack::Builder;
builder {
enable 'Deflater';
dance;
};
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"
Running multiple apps with Plack::Builder
You can use Plack::Builder to mount multiple Dancer2 applications on a PSGI webserver like
Starman.
Start by creating a simple app.psgi file:
use OurWiki; # first app
use OurForum; # second app
use Plack::Builder;
builder {
mount '/wiki' => OurWiki->dance;
mount '/forum' => OurForum->dance;
};
and now use Starman
plackup -a app.psgi -s Starman
Currently this still demands the same appdir for both (default circumstance) but in a
future version this will be easier to change while staying very simple to mount.
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 /home/myapp/myapp>
AllowOverride None
Order allow,deny
Allow from all
</Directory>
<Location />
SetHandler perl-script
PerlHandler 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>
Creating a service
You can turn your app into proper service running in background using one of the following
examples:
Using Ubic
Ubic is an extensible perlish 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);
# if your application is not installed in @INC path:
sub start {
my $self = shift;
$ENV{PERL5LIB} = '/path/to/your/application/lib';
$self->SUPER::start(@_);
}
__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 Dancer2 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/
ProxyPassReverse /mywebapp/ http://localhost:3000/
It is important for you to note that the Apache2 modules "mod_proxy" and "mod_proxy_http"
must be enabled.
a2enmod proxy
a2enmod proxy_http
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 Dancer2 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 Dancer2 app. You could even run
several instances of your Dancer2 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 Dancer2 app on port 3000:
balance http localhost:3000
To listen on a specified IP only on port 80, and distribute requests between multiple
Dancer2 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_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.
AUTHOR
Dancer Core Developers
COPYRIGHT AND LICENSE
This software is copyright (c) 2013 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.