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Mojolicious-2.08
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/ Mojolicious::Guides::Cookbook

NAME

Mojolicious::Guides::Cookbook - Cookbook

OVERVIEW

This document cotains many fun recipes for cooking with Mojolicious.

DEPLOYMENT

Getting Mojolicious and Mojolicious::Lite applications running on different platforms.

Built-in server

Mojolicious contains a very portable HTTP 1.1 compliant web server. It is usually used during development but is solid and fast enough for small to mid sized applications.

$ ./script/myapp daemon
Server available at http://127.0.0.1:3000.

It has many configuration options and is known to work on every platform Perl works on.

$ ./script/myapp help daemon
...List of available options...

Another huge advantage is that it supports TLS and WebSockets out of the box.

$ ./script/myapp daemon --listen https://*:3000
Server available at https://127.0.0.1:3000.

A development certificate for testing purposes is built right in, so it just works.

Hypnotoad

For bigger applications Mojolicious contains the UNIX optimized preforking web server Mojo::Server::Hypnotoad that will allow you to take advantage of multiple cpu cores and copy-on-write.

Mojo::Server::Hypnotoad
|- Mojo::Server::Daemon [1]
|- Mojo::Server::Daemon [2]
|- Mojo::Server::Daemon [3]
`- Mojo::Server::Daemon [4]

It is based on the normal built-in web server but optimized specifically for production environments out of the box.

$ hypnotoad script/myapp
Server available at http://127.0.0.1:8080.

Config files are plain Perl scripts for maximal customizability.

# hypnotoad.conf
{listen => ['http://*:80'], workers => 10};

But one of its biggest advantages is the support for effortless zero downtime software upgrades. That means you can upgrade Mojolicious, Perl or even system libraries at runtime without ever stopping the server or losing a single incoming connection, just by running the command above again.

$ hypnotoad script/myapp
Starting hot deployment for Hypnotoad server 31841.

You might also want to enable proxy support if you're using Hypnotoad behind a reverse proxy. This allows Mojolicious to automatically pick up the X-Forwarded-For, X-Forwarded-Host and X-Forwarded-HTTPS headers.

# hypnotoad.conf
{proxy => 1};

Nginx

One of the most popular setups these days is the built-in web server behind a Nginx reverse proxy.

upstream myapp {
  server 127.0.0.1:8080;
}
server {
  listen 80;
  server_name localhost;
  location / {
    proxy_read_timeout 300;
    proxy_pass http://myapp;
    proxy_set_header Host $host;
    proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
    proxy_set_header X-Forwarded-HTTPS 0;
  }
}

Apache/mod_proxy

Another good reverse proxy is Apache with mod_proxy, the configuration looks very similar to the Nginx one above.

<VirtualHost *:80>
  ServerName localhost
  <Proxy *>
    Order deny,allow
    Allow from all
  </Proxy>
  ProxyRequests Off
  ProxyPreserveHost On
  ProxyPass / http://localhost:8080 keepalive=On
  ProxyPassReverse / http://localhost:8080/
  RequestHeader set X-Forwarded-HTTPS "0"
</VirtualHost>

Apache/CGI

CGI is supported out of the box and your Mojolicious application will automatically detect that it is executed as a CGI script.

ScriptAlias / /home/sri/myapp/script/myapp/

PSGI/Plack

PSGI is an interface between Perl web frameworks and web servers, and Plack is a Perl module and toolkit that contains PSGI middleware, helpers and adapters to web servers. PSGI and Plack are inspired by Python's WSGI and Ruby's Rack. Mojolicious applications are ridiculously simple to deploy with Plack.

$ plackup ./script/myapp
HTTP::Server::PSGI: Accepting connections at http://0:5000/

Plack provides many server and protocol adapters for you to choose from such as FCGI, SCGI and mod_perl. Make sure to run plackup from your applications home directory, otherwise libraries might not be found.

$ plackup ./script/myapp -s FCGI -l /tmp/myapp.sock

Because plackup uses a weird trick to load your script, Mojolicious is not always able to detect the applications home directory, if that's the case you can simply use the MOJO_HOME environment variable. Also note that app->start needs to be the last Perl statement in the application script for the same reason.

$ MOJO_HOME=/home/sri/myapp plackup ./script/myapp
HTTP::Server::PSGI: Accepting connections at http://0:5000/

Some server adapters might ask for a .psgi file, if that's the case you can just point them at your application script because it will automatically act like one if it detects the presence of a PLACK_ENV environment variable.

Plack middleware

Wrapper scripts like myapp.fcgi are a great way to separate deployment and application logic.

#!/usr/bin/env plackup -s FCGI
use Plack::Builder;

builder {
  enable 'Deflater';
  require 'myapp.pl';
};

But you could even use middleware right in your application.

use Mojolicious::Lite;
use Plack::Builder;

get '/welcome' => sub {
  my $self = shift;
  $self->render(text => 'Hello Mojo!');
};

builder {
  enable 'Deflater';
  app->start;
};

Rewriting

Sometimes you might have to deploy your application in a blackbox environment where you can't just change the server configuration or behind a reverse proxy that passes along additional information with X-* headers. In such cases you can use a before_dispatch hook to rewrite incoming requests.

app->hook(before_dispatch => sub {
  my $self = shift;
  $self->req->url->base->scheme('https')
    if $self->req->headers->header('X-Forwarded-Protocol') eq 'https';
});

Embedding

From time to time you might want to reuse parts of Mojolicious applications like configuration files, database connection or helpers for other scripts, with this little mock server you can just embed them.

use Mojo::Server;

# Load application with mock server
my $server = Mojo::Server->new;
my $app = $server->load_app('./myapp.pl');

# Access fully initialized application
say $app->static->root;

You can also use the built-in web server to embed Mojolicious applications into alien environments like foreign event loops.

use Mojolicious::Lite;
use Mojo::Server::Daemon;

# Normal action
get '/' => sub {
  my $self = shift;
  $self->render(text => 'Hello World!');
};

# Connect application with custom daemon
my $daemon =
  Mojo::Server::Daemon->new(app => app, listen => ['http://*:8080']);
$daemon->prepare_ioloop;

# Call "one_tick" repeatedly from the alien environment
$daemon->ioloop->one_tick while 1;

USER AGENT

When we say Mojolicious is a web framework we actually mean it.

Web scraping

Scraping information from web sites has never been this much fun before. The built-in HTML5/XML parser Mojo::DOM supports all CSS3 selectors that make sense for a standalone parser.

# Fetch web site
my $ua = Mojo::UserAgent->new;
my $tx = $ua->get('mojolicio.us/perldoc');

# Extract title
say 'Title: ', $tx->res->dom->at('head > title')->text;

# Extract headings
$tx->res->dom('h1, h2, h3')->each(sub {
  say 'Heading: ', shift->all_text;
});

Especially for unit testing your Mojolicious applications this can be a very powerful tool.

JSON web services

Most web services these days are based on the JSON data-interchange format. That's why Mojolicious comes with the possibly fastest pure-Perl implementation Mojo::JSON built right in.

# Fresh user agent
my $ua = Mojo::UserAgent->new;

# Fetch the latest news about Mojolicious from Twitter
my $search = 'http://search.twitter.com/search.json?q=Mojolicious';
for $tweet (@{$ua->get($search)->res->json->{results}}) {

  # Tweet text
  my $text = $tweet->{text};

  # Twitter user
  my $user = $tweet->{from_user};

  # Show both
  my $result = "$text --$user";
  utf8::encode $result;
  say $result;
}

Basic authentication

You can just add username and password to the URL.

my $ua = Mojo::UserAgent->new;
say $ua->get('https://sri:secret@mojolicio.us/hideout')->res->body;

Decorating followup requests

Mojo::UserAgent can automatically follow redirects, the on_start callback allows you direct access to each transaction right after they have been initialized and before a connection gets associated with them.

# User agent following up to 10 redirects
my $ua = Mojo::UserAgent->new(max_redirects => 10);

# Add a witty header to every request
$ua->on(start => sub {
  my ($ua, $tx) = @_;
  $tx->req->headers->header('X-Bender' => 'Bite my shiny metal ass!');
  say 'Request: ', $tx->req->url->clone->to_abs;
});

# Request that will most likely get redirected
say 'Title: ', $ua->get('google.com')->res->dom->at('head > title')->text;

This even works for proxy CONNECT requests.

Streaming response

Receiving a streaming response can be really tricky in most HTTP clients, Mojo::UserAgent makes it actually easy.

my $ua = Mojo::UserAgent->new;
my $tx = $ua->build_tx(GET => 'http://mojolicio.us');
$tx->res->body(sub { say $_[1] });
$ua->start($tx);

The body callback will be called for every chunk of data that is received, even chunked encoding will be handled transparently if necessary.

Streaming request

Sending a streaming request is almost just as easy.

my $ua      = Mojo::UserAgent->new;
my $tx      = $ua->build_tx(GET => 'http://mojolicio.us');
my $content = 'Hello world!';
$tx->req->headers->content_length(length $content);
my $drain;
$drain = sub {
  my $req   = shift;
  my $chunk = substr $content, 0, 1, '';
  $drain    = undef unless length $content;
  $req->write($chunk, $drain);
};
$drain->($tx->req);
$ua->start($tx);

The drain callback passed to write will be invoked whenever the entire previous chunk has actually been written.

Large file downloads

When downloading large files with Mojo::UserAgent you don't have to worry about memory usage at all, because it will automatically stream everything above 250KB into a temporary file.

# Lets fetch the latest Mojolicious tarball
my $ua = Mojo::UserAgent->new(max_redirects => 5);
my $tx = $ua->get('latest.mojolicio.us');
$tx->res->content->asset->move_to('mojo.tar.gz');

To protect you from excessively large files there is also a global limit of 5MB by default, which you can tweak with the MOJO_MAX_MESSAGE_SIZE environment variable.

# Increase limit to 1GB
$ENV{MOJO_MAX_MESSAGE_SIZE} = 1073741824;

Large file upload

Uploading a large file is even easier.

# Upload file via POST and "multipart/form-data"
my $ua = Mojo::UserAgent->new;
$ua->post_form('mojolicio.us/upload',
  {image => {file => '/home/sri/hello.png'}});

And once again you don't have to worry about memory usage, all data will be streamed directly from the file.

# Upload file via PUT
my $ua     = Mojo::UserAgent->new;
my $asset  = Mojo::Asset::File->new(path => '/home/sri/hello.png');
my $tx     = $ua->build_tx(PUT => 'mojolicio.us/upload');
$tx->req->content->asset($asset);
$ua->start($tx);

Non-blocking

Mojo::UserAgent has been designed from the ground up to be non-blocking, the whole blocking API is just a simple convenience wrapper. Especially for high latency tasks like web crawling this can be extremely useful, because you can keep many parallel connections active at the same time.

# FIFO queue
my @urls = ('google.com');

# User agent following up to 5 redirects
my $ua = Mojo::UserAgent->new(max_redirects => 5);

# Crawler
my $crawl;
$crawl = sub {
  my $id = shift;

  # Dequeue or wait for more URLs
  return Mojo::IOLoop->timer(2 => sub { $crawl->($id) })
    unless my $url = shift @urls;

  # Fetch non-blocking just by adding a callback
  $ua->get($url => sub {
    my ($ua, $tx) = @_;

    # Extract URLs
    say "[$id] $url";
    $tx->res->dom('a[href]')->each(sub {
      my $e = shift;

      # Build absolute URL
      my $url = Mojo::URL->new($e->{href})->to_abs($tx->req->url);
      say " -> $url";

      # Enqueue
      push @urls, $url;
    });

    # Next
    $crawl->($id);
  });
};

# Start a bunch of parallel crawlers sharing the same user agent
$crawl->($_) for 1 .. 3;

# Start event loop
Mojo::IOLoop->start;

You can take full control of the Mojo::IOLoop event loop.

Parallel blocking requests

You can emulate blocking behavior by using a Mojo::IOLoop trigger to synchronize multiple non-blocking requests.

# Synchronize non-blocking requests and capture result
my $ua = Mojo::UserAgent->new;
my $t  = Mojo::IOLoop->trigger;
$ua->get('http://mojolicio.us'         => $t->begin);
$ua->get('http://mojolicio.us/perldoc' => $t->begin);
my ($tx, $tx2) = $t->start;

Just be aware that the resulting transactions will be in random order.

Command line

Don't you hate checking huge HTML files from the command line? Thanks to the mojo get command that is about to change. You can just pick the parts that actually matter with the CSS3 selectors from Mojo::DOM.

$ mojo get http://mojolicio.us 'head > title'

How about a list of all id attributes?

$ mojo get http://mojolicio.us '*' attr id

Or the text content of all heading tags?

$ mojo get http://mojolicio.us 'h1, h2, h3' text

Maybe just the text of the third heading?

$ mojo get http://mojolicio.us 'h1, h2, h3' 3 text

You can also extract all text from nested child elements.

$ mojo get http://mojolicio.us '#mojobar' all

The request can be customized as well.

$ mojo get --method post --content 'Hello!' http://mojolicio.us
$ mojo get --header 'X-Bender: Bite my shiny metal ass!' http://google.com

You can follow redirects and view the headers for all messages.

$ mojo get --redirect --verbose http://reddit.com 'head > title'

This can be an invaluable tool for testing your applications.

$ ./myapp.pl get /welcome 'head > title'

HACKS

Fun hacks you might not use very often but that might come in handy some day.

Faster tests

Don't you hate waiting for make test to finally finish? In newer Perl versions you can set the HARNESS_OPTIONS environment variable to take advantage of multiple cpu cores and run tests parallel.

$ HARNESS_OPTIONS=j5 make test
...

The j5 allows 5 tests to run at the same time, which makes for example the Mojolicious test suite finish 3 times as fast on a dual core laptop!

Adding commands to Mojolicious

By now you've propably used many of the built-in commands described in Mojolicious::Commands, but did you know that you can just add new ones and that they will be picked up automatically by the command line interface?

package Mojolicious::Command::spy;
use Mojo::Base 'Mojo::Command';

sub run {
  my ($self, $whatever) = @_;

  # Leak secret passphrase
  if ($whatever eq 'secret') {
    my $secret = $self->app->secret;
    say qq/The secret of this application is "$secret"./;
  }
}

1;

There are many more useful methods and attributes in Mojo::Command that you can use or overload.

$ mojo spy secret
The secret of this application is "Mojolicious::Lite".

$ ./myapp.pl spy secret
The secret of this application is "secr3t".

Running code against your application

Ever thought about running a quick oneliner against your Mojolicious application to test something? Thanks to the eval command you can do just that, the application instance itself can be accessed via app.

$ mojo generate lite_app
$ ./myapp.pl eval 'say app->static->root'

The verbose option will automatically print the return value to STDOUT.

$ ./myapp.pl eval -v 'app->static->root'

Making your application installable

Ever thought about releasing your Mojolicious application to CPAN? It's actually much easier than you might think.

$ mojo generate app
$ cd my_mojolicious_app
$ mv public lib/MyMojoliciousApp/
$ mv templates lib/MyMojoliciousApp/

The trick is to move the public and templates directories so they can get automatically installed with the modules.

package MyMojoliciousApp;
use Mojo::Base 'Mojolicious';

use File::Basename 'dirname';
use File::Spec;

# Every CPAN module needs a version
our $VERSION = '1.0';

sub startup {
  my $self = shift;

  # Switch to installable home directory
  $self->home->parse(
    File::Spec->catdir(dirname(__FILE__), 'MyMojoliciousApp'));

  # Switch to installable "public" directory
  $self->static->root($self->home->rel_dir('public'));

  # Switch to installable "templates" directory
  $self->renderer->root($self->home->rel_dir('templates'));

  $self->plugin('PODRenderer');

  my $r = $self->routes;
  $r->route('/welcome')->to('example#welcome');
}

1;

That's really everything, now you can package your application like any other CPAN module.

$ ./script/my_mojolicious_app generate makefile
$ perl Makefile.PL
$ make test
$ make manifest
$ make dist

And if you have a PAUSE account (which can be requested at http://pause.perl.org) even upload it.

$ mojo cpanify -u USER -p PASS MyMojoliciousApp-0.01.tar.gz

Hello World

If every byte matters this is the smallest Hello World application you can write with Mojolicious::Lite.

use Mojolicious::Lite;
any {text => 'Hello World!'};
app->start;

It works because all routes without a pattern default to / and automatic rendering kicks in even if no actual code gets executed by the router. The renderer just picks up the text value from the stash and generates a response.

Hello World oneliner

The Hello World example above can get even a little bit shorter in an ojo oneliner.

perl -Mojo -e'a({text => "Hello World!"})->start' daemon

And you can use all the commands from Mojolicious::Commands.

perl -Mojo -e'a({text => "Hello World!"})->start' get -v /

jQuery (Content Distribution Network)

These days Mojolicious ships with a bundled version of jQuery, which you can easily use as a fallback for applications that might be used offline from time to time.

<%= javascript
  'http://ajax.googleapis.com/ajax/libs/jquery/1.6/jquery.min.js' %>
%= javascript begin
  if (typeof jQuery == 'undefined') {
    var e = document.createElement('script');
    e.src = '/js/jquery.js';
    e.type = 'text/javascript';
    document.getElementsByTagName("head")[0].appendChild(e);
  }
% end

MORE

You can continue with Mojolicious::Guides now or take a look at the Mojolicious wiki http://github.com/kraih/mojo/wiki, which contains a lot more documentation and examples by many different authors.