Provided by: libdancer2-perl_0.400001+dfsg-1_all 
NAME
Dancer2::Manual::Deployment - common ways to put your Dancer app into use
VERSION
version 0.400001
DESCRIPTION
Dancer has been designed to be flexible, and this flexibility extends to your choices when
deploying your Dancer app.
Running stand-alone
To start your application, just run plackup:
$ plackup bin/app.psgi
HTTP::Server::PSGI: Accepting connections at http://0:5000/
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 the Application
While developing your application, it is often handy to have the server automatically
reload your application when changes are made. There are two recommended ways of handling
this with Dancer: using " plackup -r " and Plack::Loader::Shotgun. Both have their
advantages and disadvantages (which will be explained below).
Regardless of the method you use, it is not recommended that you automatically reload
your applications in a production environment, for reasons of performance, deployment best
practices, etc.
For Dancer 1 programmers that used the " auto_reload " option, please use one of these
alternatives instead:
Auto reloading with " plackup -r "
Plack's built-in reloader will reload your application anytime a file in your
application's directory (usually, /bin ) changes. You will likely want to monitor your
lib/ directory too, using the " -R " option:
$ plackup -r -R lib bin/app.psgi
There is a performance hit associated with this, as Plack will spin off a separate process
that monitors files in the application and other specified directories. If the timestamp
of any files in a watched directory changes, the application is recompiled and reloaded.
See the plackup docs for more information on the " -r " and " -R " options.
Auto reloading with plackup and Shotgun
There may be circumstances where Plack's built-in reloader won't work for you, be it for
the way it looks for changes, or because there are many directories you need to monitor,
or you want to reload the application any time one of the modules in Perl's lib/ path
changes. Plack::Loader::Shotgun makes this easy by recompiling the application on every
request.
To use Shotgun, specify it using the loader argument to " plackup (-L) ":
$ plackup -L Shotgun bin/app.psgi
The Shotgun, while effective, can quickly cause you performance issues, even during the
development phase of your application. As the number of plugins you use in your
application grows, as the number of static resources (images, etc.) grows, the more
requests your server process needs to handle. Since each request recompiles the
application, even simple page refreshes can get unbearably slow over time. Use with
caution.
You can bypass Shotgun's auto-reloading of specific modules with the " -M " switch:
$ plackup -L Shotgun -M<MyApp::Foo> -M<MyApp::Bar> bin/app.psgi
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.psgi
HTTP::Server::PSGI: Accepting connections at http://0:5000/
Please note: if you are using Dancer 2's asynchronous capabilities, using Shotgun will
kill Twiggy. If you need async processing, consider an alternative to Shotgun.
Running under Apache
You can run your Dancer app from Apache using the following examples:
As a CGI script
In its simplest form, your Dancer app can be run as a simple CGI script out-of-the-box.
You will need to enable the Apache mod_cgi or mod_cgid modules ("a2enmod cgi" or "a2enmod
cgid" on Debian-based systems) and mod_rewrite ("a2enmod rewrite"). The Perl module
Plack::Runner is required.
The following is an example apache configuration. Depending on your Apache configuration
layout, this should be placed in "httpd.conf" or "sites-available/*site*". The
configuration options can also be placed in ".htaccess" files if you prefer.
<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
AddHandler cgi-script .cgi
# Apache 2.2
Order allow,deny
Allow from all
# Apache 2.4
Require all granted
</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>
Now you can access your dancer application URLs as if you were using the embedded web
server.
http://www.example.com/
This option is a no-brainer, easy to setup and low maintenance, but serves requests slower
than all other options, as each time a request is made to your server, Apache will start
your application. This might be suitable for a small, occasionally-used sites, as the
application is not using resources when it is not being accessed. For anything more, you
probably want to use FastCGI instead (see next section).
To list all currently loaded modules, type "apachectl -M" ("apache2ctl -M" on
Debian/Ubuntu).
As a FastCGI script
This has all the easy-to-setup and low-maintenance advantages of CGI, but is much faster
for each request, as it keeps a copy of the application running all the time.
You will still need to enable "mod_rewrite", but will need to use a FastCGI module instead
of a CGI module. There are 3 available: mod_fcgid <http://httpd.apache.org/mod_fcgid/>,
mod_fastcgi <http://www.fastcgi.com/> and mod_proxy_fcgi
<https://httpd.apache.org/docs/trunk/mod/mod_proxy_fcgi.html>. For this example, we will
use mod_fastcgi ("a2enmod fastcgi" in Debian).
The CGI configuration above now changes as follows (differences highlighted with XXX):
<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
# XXX Start a FastCGI server to run in the background
FastCgiServer /srv/www.example.com/public/dispatch.fcgi
<Directory "/srv/www.example.com/public">
AllowOverride None
Options +ExecCGI -MultiViews +SymLinksIfOwnerMatch
# XXX Use FastCGI handler instead of CGI
AddHandler fastcgi-script .fcgi
# Apache 2.2
Order allow,deny
Allow from all
# Apache 2.4
Require all granted
</Directory>
RewriteEngine On
RewriteCond %{REQUEST_FILENAME} !-f
# Run FastCGI dispatcher instead of CGI dispatcher
RewriteRule ^(.*)$ /dispatch.fcgi$1 [QSA,L]
ErrorLog /var/log/apache2/www.example.com-error.log
CustomLog /var/log/apache2/www.example.com-access_log common
</VirtualHost>
This is the easiest way to get a production server up and running, as there is no need to
worry about daemonizing your application. Apache manages all that for you.
Reloading your application
You can use "apache2ctl restart" or "apache2ctl graceful" to reload your application. The
latter will be more friendly to your users in a production environment. If your
application loads relatively quickly, then it should go unnoticed.
Configuration
See <http://www.fastcgi.com/mod_fastcgi/docs/mod_fastcgi.html> for FastCGI configuration
options. An example configuration:
FastCgiServer /srv/www.example.com/public/dispatch.fcgi -processes 5 -initial-env DANCER_ENVIRONMENT="production"
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
PerlResponseHandler Plack::Handler::Apache2
PerlSetVar psgi_app /websites/myapp.example.com/app.psgi
</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>
Running multiple applications under the same virtualhost
If you want to deploy multiple applications under the same "VirtualHost" (using one
application per directory, for example) you can use the following example Apache
configuration.
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 PSGI-based Perl webservers
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,
multiple interfaces, graceful restarts and dynamic worker pool configuration.
Twiggy
"Twiggy" is an "AnyEvent" web server, it's light and fast.
Corona
"Corona" is a "Coro" based web server.
Similar to running standalone, use plackup to start your application (see Plack and
specific servers above for all available options):
$ plackup bin/app.psgi
$ plackup -E deployment -s Starman --workers=10 -p 5001 -a bin/app.psgi
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 the "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".
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.psgi',
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.psgi -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. Also, in this case you might want to look at the "behind_proxy"
configuration option, to make sure that all the URLs are constructed properly.
behind_proxy: 1
This setup can 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 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 Lighttpd'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.
Using HAProxy
"HAProxy" is a reliable high-performance TCP/HTTP load balancer written in C available
from <https://www.haproxy.org/>.
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
Running on lighttpd
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.psgi
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.psgi
Performance Improvements
The following modules can be used to speed up an app in Dancer2:
• CGI::Deurl::XS
• Class::XSAccessor
• Cpanel::JSON::XS
• Crypt::URandom
• HTTP::XSCookies
• HTTP::XSHeaders
• Math::Random::ISAAC::XS
• MooX::TypeTiny
• Type::Tiny::XS
• URL::Encode::XS
• YAML::XS
If you generated your application with "dancer2 gen", you can easily install these with
the following command:
cpanm --installdeps . --with-feature=accelerate
To build them, you will need access to a C compiler, and using these modules will prevent
you from fatpacking your application.
These modules are installed by default when building a Docker container containing your
application.
AUTHOR
Dancer Core Developers
COPYRIGHT AND LICENSE
This software is copyright (c) 2023 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.