Mojolicious::Guides::Cookbook(3)

NAME
Mojolicious::Guides::Cookbook - Cookbook

OVERVIEW
This document contains many fun recipes for cooking with Mojolicious.

DEPLOYMENT
Getting Mojolicious and Mojolicious::Lite applications running on different platforms. Note that many real-time web features are based on the Mojo::IOLoop event loop, and therefore require one of the built-in web servers to be able to use them to their full potential.

  Built-in web server
Mojolicious contains a very portable non-blocking I/O HTTP and WebSocket server with Mojo::Server::Daemon. It is usually used during development and in the construction of more advanced web servers, but is solid and fast enough for small to mid sized applications.

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

It is available to every application through the command Mojolicious::Command::daemon, which has many configuration options and is known to work on every platform Perl works on with its single-process architecture.

  $ ./script/my_app daemon -h
  ...List of available options...

Another huge advantage is that it supports TLS and WebSockets out of the box, a development certificate for testing purposes is built right in, so it just works, but you can specify all listen locations supported by "listen" in Mojo::Server::Daemon.

  $ ./script/my_app daemon -l https://[::]:3000
  Server available at https://[::]:3000

On UNIX platforms you can also add preforking and switch to a multi-process architecture with Mojolicious::Command::prefork, to take advantage of multiple CPU cores and copy-on-write memory management.

  $ ./script/my_app prefork
  Server available at http://127.0.0.1:3000

Since all built-in web servers are based on the Mojo::IOLoop event loop, they scale best with non-blocking operations. But if your application for some reason needs to perform many blocking operations, you can improve performance by increasing the number of worker processes and decreasing the number of concurrent connections each worker is allowed to handle (often as low as 1).

  $ ./script/my_app prefork -m production -w 10 -c 1
  Server available at http://127.0.0.1:3000

During startup your application is preloaded in the manager process, which does not run an event loop, so you can use "next_tick" in Mojo::IOLoop to run code whenever a new worker process has been forked and its event loop gets started.

  use Mojolicious::Lite;

  Mojo::IOLoop->next_tick(sub {
    app->log->info("Worker $$ star...ALL GLORY TO THE HYPNOTOAD!");
  });

  get '/' => {text => 'Hello Wor...ALL GLORY TO THE HYPNOTOAD!'};

  app->start;

  Morbo
After reading the Mojolicious::Guides::Tutorial, you should already be familiar with Mojo::Server::Morbo.

  Mojo::Server::Morbo
  +- Mojo::Server::Daemon

It is basically a restarter that forks a new Mojo::Server::Daemon web server whenever a file in your project changes, and should therefore only be used during development. To start applications with it you can use the morbo script.

  $ morbo ./script/my_app
  Server available at http://127.0.0.1:3000

  Hypnotoad
For bigger applications Mojolicious contains the UNIX optimized preforking web server Mojo::Server::Hypnotoad, which can take advantage of multiple CPU cores and copy-on-write memory management to scale up to thousands of concurrent client connections.

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

It is based on the Mojo::Server::Prefork web server, which adds preforking to Mojo::Server::Daemon, but optimized specifically for production environments out of the box. To start applications with it you can use the hypnotoad script, which listens on port 8080, automatically daemonizes the server process and defaults to "production" mode for Mojolicious and Mojolicious::Lite applications.

  $ hypnotoad ./script/my_app

Many configuration settings can be tweaked right from within your application with "config" in Mojo, for a full list see "SETTINGS" in Mojo::Server::Hypnotoad.

  use Mojolicious::Lite;

  app->config(hypnotoad => {listen => ['http://*:80']});

  get '/' => {text => 'Hello Wor...ALL GLORY TO THE HYPNOTOAD!'};

  app->start;

Or just add a "hypnotoad" section to your Mojolicious::Plugin::Config or Mojolicious::Plugin::JSONConfig configuration file.

  # myapp.conf
  {
    hypnotoad => {
      listen  => ['https://*:443?cert=/etc/server.crt&key=/etc/server.key'],
      workers => 10
    }
  };

But one of its biggest advantages is the support for effortless zero downtime software upgrades (hot deployment). 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/my_app
  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" and "X-Forwarded-Proto" headers.

  # myapp.conf
  {hypnotoad => {proxy => 1}};

  Zero downtime software upgrades
Hypnotoad makes zero downtime software upgrades (hot deployment) very simple, as you can see above, but on modern operating systems that support the "SO_REUSEPORT" socket option, there is also another method available that works with all built-in web servers.

  $ ./script/my_app prefork -P /tmp/first.pid -l http://*:8080?reuse=1
  Server available at http://127.0.0.1:8080

All you have to do is start a second web server listening to the same port and stop the first web server gracefully afterwards.

  $ ./script/my_app prefork -P /tmp/second.pid -l http://*:8080?reuse=1
  Server available at http://127.0.0.1:8080
  $ kill -s TERM `cat /tmp/first.pid`

Just remember that both web servers need to be started with the "reuse" parameter.

  Nginx
One of the most popular setups these days is Hypnotoad behind an Nginx <http://nginx.org> reverse proxy, which even supports WebSockets in newer versions.

  upstream myapp {
    server 127.0.0.1:8080;
  }
  server {
    listen 80;
    server_name localhost;
    location / {
      proxy_pass http://myapp;
      proxy_http_version 1.1;
      proxy_set_header Upgrade $http_upgrade;
      proxy_set_header Connection "upgrade";
      proxy_set_header Host $host;
      proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
      proxy_set_header X-Forwarded-Proto $scheme;
    }
  }

  Apache/mod_proxy
Another good reverse proxy is Apache <http://httpd.apache.org> with "mod_proxy", the configuration looks quite 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-Proto "http"
  </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. Its use in production environments is discouraged though, because as a result of how "CGI" works, it is very slow and many web servers are making it exceptionally hard to configure properly.

  ScriptAlias / /home/sri/my_app/script/my_app/

  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/my_app

Plack provides many server and protocol adapters for you to choose from, such as "FCGI", "uWSGI" and "mod_perl".

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

The "MOJO_REVERSE_PROXY" environment variable can be used to enable proxy support, this allows Mojolicious to automatically pick up the "X-Forwarded-For" and "X-Forwarded-Proto" headers.

  $ MOJO_REVERSE_PROXY=1 plackup ./script/my_app

If an older server adapter is unable to correctly detect the application home directory, you can simply use the "MOJO_HOME" environment variable.

  $ MOJO_HOME=/home/sri/my_app plackup ./script/my_app

There is no need for a ".psgi" file, just point the server adapter at your application script, 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 './script/my_app';
  };

Mojo::Server::PSGI can be used directly to load and customize applications in the wrapper script.

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

  builder {
    enable 'Deflater';
    my $server = Mojo::Server::PSGI->new;
    $server->load_app('./script/my_app');
    $server->app->config(foo => 'bar');
    $server->to_psgi_app;
  };

But you could even use middleware right in your application.

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

  get '/welcome' => sub {
    my $c = shift;
    $c->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 the hook "before_dispatch" in Mojolicious to rewrite incoming requests.

  # Change scheme if "X-Forwarded-HTTPS" header is set
  $app->hook(before_dispatch => sub {
    my $c = shift;
    $c->req->url->base->scheme('https')
      if $c->req->headers->header('X-Forwarded-HTTPS');
  });

Since reverse proxies generally don't pass along information about path prefixes your application might be deployed under, rewriting the base path of incoming requests is also quite common.

  # Move first part and slash from path to base path in production mode
  $app->hook(before_dispatch => sub {
    my $c = shift;
    push @{$c->req->url->base->path->trailing_slash(1)},
      shift @{$c->req->url->path->leading_slash(0)};
  }) if $app->mode eq 'production';

Mojo::URL objects are very easy to manipulate, just make sure that the URL ("foo/bar?baz=yada"), which represents the routing destination, is always relative to the base URL ("http://example.com/myapp/"), which represents the deployment location of your application.

  Application 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 Mojo::Server based 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 for @{$app->static->paths};
  say $app->config->{secret_identity};
  say $app->dumper({just => 'a helper test'});
  say $app->build_controller->render_to_string(template => 'foo');

The plugin Mojolicious::Plugin::Mount uses this functionality to allow you to combine multiple applications into one and deploy them together.

  use Mojolicious::Lite;

  plugin Mount => {'test1.example.com' => '/home/sri/myapp1.pl'};
  plugin Mount => {'test2.example.com' => '/home/sri/myapp2.pl'};

  app->start;

  Web server embedding
You can also use "one_tick" in Mojo::IOLoop to embed the built-in web server Mojo::Server::Daemon into alien environments like foreign event loops that for some reason can't just be integrated with a new reactor backend.

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

  # Normal action
  get '/' => {text => 'Hello World!'};

  # Connect application with web server and start accepting connections
  my $daemon
    = Mojo::Server::Daemon->new(app => app, listen => ['http://*:8080']);
  $daemon->start;

  # Call "one_tick" repeatedly from the alien environment
  Mojo::IOLoop->one_tick while 1;

REAL-TIME WEB
The real-time web is a collection of technologies that include Comet (long polling), EventSource and WebSockets, which allow content to be pushed to consumers with long-lived connections as soon as it is generated, instead of relying on the more traditional pull model. All built-in web servers use non-blocking I/O and are based on the Mojo::IOLoop event loop, which provides many very powerful features that allow real-time web applications to scale up to thousands of concurrent client connections.

  Backend web services
Since Mojo::UserAgent is also based on the Mojo::IOLoop event loop, it won't block the built-in web servers when used non-blocking, even for high latency backend web services.

  use Mojolicious::Lite;

  # Search MetaCPAN for "mojolicious"
  get '/' => sub {
    my $c = shift;
    $c->ua->get('api.metacpan.org/v0/module/_search?q=mojolicious' => sub {
      my ($ua, $tx) = @_;
      $c->render('metacpan', hits => $tx->res->json->{hits}{hits});
    });
  };

  app->start;
  __DATA__

  @@ metacpan.html.ep
  <!DOCTYPE html>
  <html>
    <head><title>MetaCPAN results for "mojolicious"</title></head>
    <body>
      % for my $hit (@$hits) {
        <p><%= $hit->{_source}{release} %></p>
      % }
    </body>
  </html>

  Synchronizing events
Multiple events such as concurrent requests can be easily synchronized with "delay" in Mojolicious::Plugin::DefaultHelpers, which can help you avoid deep nested closures that often result from continuation-passing style.

  use Mojolicious::Lite;
  use Mojo::URL;

  # Search MetaCPAN for "mojo" and "minion"
  get '/' => sub {
    my $c = shift;

    # Prepare response in two steps
    $c->delay(

      # Concurrent requests
      sub {
        my $delay = shift;
        my $url   = Mojo::URL->new('api.metacpan.org/v0/module/_search');
        $url->query({sort => 'date:desc'});
        $c->ua->get($url->clone->query({q => 'mojo'})   => $delay->begin);
        $c->ua->get($url->clone->query({q => 'minion'}) => $delay->begin);
      },

      # Delayed rendering
      sub {
        my ($delay, $mojo, $minion) = @_;
        $c->render(json => {
          mojo   => $mojo->res->json('/hits/hits/0/_source/release'),
          minion => $minion->res->json('/hits/hits/0/_source/release')
        });
      }
    );
  };

  app->start;

  Timers
Timers, another primary feature of the event loop, are created with "timer" in Mojo::IOLoop and can for example be used to delay rendering of a response, and unlike "sleep", won't block any other requests that might be processed concurrently.

  use Mojolicious::Lite;
  use Mojo::IOLoop;

  # Wait 3 seconds before rendering a response
  get '/' => sub {
    my $c = shift;
    Mojo::IOLoop->timer(3 => sub {
      $c->render(text => 'Delayed by 3 seconds!');
    });
  };

  app->start;

Recurring timers created with "recurring" in Mojo::IOLoop are slightly more powerful, but need to be stopped manually, or they would just keep getting emitted.

  use Mojolicious::Lite;
  use Mojo::IOLoop;

  # Count to 5 in 1 second steps
  get '/' => sub {
    my $c = shift;

    # Start recurring timer
    my $i = 1;
    my $id = Mojo::IOLoop->recurring(1 => sub {
      $c->write_chunk($i);
      $c->finish if $i++ == 5;
    });

    # Stop recurring timer
    $c->on(finish => sub { Mojo::IOLoop->remove($id) });
  };

  app->start;

Timers are not tied to a specific request or connection, and can even be created at startup time.

  use Mojolicious::Lite;
  use Mojo::IOLoop;

  # Check title in the background every 10 seconds
  my $title = 'Got no title yet.';
  Mojo::IOLoop->recurring(10 => sub {
    app->ua->get('http://mojolicio.us' => sub {
      my ($ua, $tx) = @_;
      $title = $tx->res->dom->at('title')->text;
    });
  });

  # Show current title
  get '/' => sub {
    my $c = shift;
    $c->render(json => {title => $title});
  };

  app->start;

Just remember that all events are processed cooperatively, so your callbacks shouldn't block for too long.

  Exceptions in events
Since timers and other non-blocking operations are running solely in the event loop, outside of the application, exceptions that get thrown in callbacks can't get caught and handled automatically. But you can handle them manually by subscribing to the event "error" in Mojo::Reactor or catching them inside the callback.

  use Mojolicious::Lite;
  use Mojo::IOLoop;

  # Forward error messages to the application log
  Mojo::IOLoop->singleton->reactor->on(error => sub {
    my ($reactor, $err) = @_;
    app->log->error($err);
  });

  # Exception only gets logged (and connection times out)
  get '/connection_times_out' => sub {
    my $c = shift;
    Mojo::IOLoop->timer(2 => sub {
      die 'This request will not be getting a response';
    });
  };

  # Exception gets caught and handled
  get '/catch_exception' => sub {
    my $c = shift;
    Mojo::IOLoop->timer(2 => sub {
      eval { die 'This request will be getting a response' };
      $c->reply->exception($@) if $@;
    });
  };

  app->start;

A default subscriber that turns all errors into warnings will usually be added by Mojo::IOLoop as a fallback.

  Mojo::IOLoop->singleton->reactor->unsubscribe('error');

During development or for applications where crashing is simply preferable, you can also make every exception that gets thrown in a callback fatal by removing all of its subscribers.

  WebSocket web service
The WebSocket protocol offers full bi-directional low-latency communication channels between clients and servers. Receive messages just by subscribing to events such as "message" in Mojo::Transaction::WebSocket with "on" in Mojolicious::Controller and return them with "send" in Mojolicious::Controller.

  use Mojolicious::Lite;

  # Template with browser-side code
  get '/' => 'index';

  # WebSocket echo service
  websocket '/echo' => sub {
    my $c = shift;

    # Opened
    $c->app->log->debug('WebSocket opened');

    # Increase inactivity timeout for connection a bit
    $c->inactivity_timeout(300);

    # Incoming message
    $c->on(message => sub {
      my ($c, $msg) = @_;
      $c->send("echo: $msg");
    });

    # Closed
    $c->on(finish => sub {
      my ($c, $code, $reason) = @_;
      $c->app->log->debug("WebSocket closed with status $code");
    });
  };

  app->start;
  __DATA__

  @@ index.html.ep
  <!DOCTYPE html>
  <html>
    <head><title>Echo</title></head>
    <body>
      <script>
        var ws = new WebSocket('<%= url_for('echo')->to_abs %>');

        // Incoming messages
        ws.onmessage = function (event) {
          document.body.innerHTML += event.data + '<br/>';
        };

        // Outgoing messages
        ws.onopen = function (event) {
          window.setInterval(function () { ws.send('Hello Mojo!') }, 1000);
        };
      </script>
    </body>
  </html>

The event "finish" in Mojo::Transaction::WebSocket will be emitted right after the WebSocket connection has been closed.

  $c->tx->with_compression;

You can activate "permessage-deflate" compression with "with_compression" in Mojo::Transaction::WebSocket, this can result in much better performance, but also increases memory usage by up to 300KB per connection.

  Testing WebSocket web services
While the message flow on WebSocket connections can be rather dynamic, it more often than not is quite predictable, which allows this rather pleasant Test::Mojo API to be used.

  use Test::More;
  use Test::Mojo;

  # Include application
  use FindBin;
  require "$FindBin::Bin/../echo.pl";

  # Test echo web service
  my $t = Test::Mojo->new;
  $t->websocket_ok('/echo')
    ->send_ok('Hello Mojo!')
    ->message_ok
    ->message_is('echo: Hello Mojo!')
    ->finish_ok;

  # Test JSON web service
  $t->websocket_ok('/echo.json')
    ->send_ok({json => {test => [1, 2, 3]}})
    ->message_ok
    ->json_message_is('/test', [1, 2, 3])
    ->finish_ok;

  done_testing();

  EventSource web service
EventSource is a special form of long polling where you can use "write" in Mojolicious::Controller to directly send DOM events from servers to clients. It is uni-directional, that means you will have to use Ajax requests for sending data from clients to servers, the advantage however is low infrastructure requirements, since it reuses the HTTP protocol for transport.

  use Mojolicious::Lite;

  # Template with browser-side code
  get '/' => 'index';

  # EventSource for log messages
  get '/events' => sub {
    my $c = shift;

    # Increase inactivity timeout for connection a bit
    $c->inactivity_timeout(300);

    # Change content type and finalize response headers
    $c->res->headers->content_type('text/event-stream');
    $c->write;

    # Subscribe to "message" event and forward "log" events to browser
    my $cb = $c->app->log->on(message => sub {
      my ($log, $level, @lines) = @_;
      $c->write("event:log\ndata: [$level] @lines\n\n");
    });

    # Unsubscribe from "message" event again once we are done
    $c->on(finish => sub {
      my $c = shift;
      $c->app->log->unsubscribe(message => $cb);
    });
  };

  app->start;
  __DATA__

  @@ index.html.ep
  <!DOCTYPE html>
  <html>
    <head><title>LiveLog</title></head>
    <body>
      <script>
        var events = new EventSource('<%= url_for 'events' %>');

        // Subscribe to "log" event
        events.addEventListener('log', function (event) {
          document.body.innerHTML += event.data + '<br/>';
        }, false);
      </script>
    </body>
  </html>

The event "message" in Mojo::Log will be emitted for every new log message and the event "finish" in Mojo::Transaction right after the transaction has been finished.

  Streaming multipart uploads
Mojolicious contains a very sophisticated event system based on Mojo::EventEmitter, with ready-to-use events on almost all layers, and which can be combined to solve some of hardest problems in web development.

  use Mojolicious::Lite;
  use Scalar::Util 'weaken';

  # Intercept multipart uploads and log each chunk received
  hook after_build_tx => sub {
    my $tx = shift;

    # Subscribe to "upgrade" event to indentify multipart uploads
    weaken $tx;
    $tx->req->content->on(upgrade => sub {
      my ($single, $multi) = @_;
      return unless $tx->req->url->path->contains('/upload');

      # Subscribe to "part" event to find the right one
      $multi->on(part => sub {
        my ($multi, $single) = @_;

        # Subscribe to "body" event of part to make sure we have all headers
        $single->on(body => sub {
          my $single = shift;

          # Make sure we have the right part and replace "read" event
          return unless $single->headers->content_disposition =~ /example/;
          $single->unsubscribe('read')->on(read => sub {
            my ($single, $bytes) = @_;

            # Log size of every chunk we receive
            app->log->debug(length($bytes) . ' bytes uploaded');
          });
        });
      });
    });
  };

  # Upload form in DATA section
  get '/' => 'index';

  # Streaming multipart upload
  post '/upload' => {text => 'Upload was successful.'};

  app->start;
  __DATA__

  @@ index.html.ep
  <!DOCTYPE html>
  <html>
    <head><title>Streaming multipart upload</title></head>
    <body>
      %= form_for upload => (enctype => 'multipart/form-data') => begin
        %= file_field 'example'
        %= submit_button 'Upload'
      % end
    </body>
  </html>

  Event loops
Internally the Mojo::IOLoop event loop can use multiple reactor backends, EV for example will be automatically used if possible. Which in turn allows other event loops like AnyEvent to just work.

  use Mojolicious::Lite;
  use EV;
  use AnyEvent;

  # Wait 3 seconds before rendering a response
  get '/' => sub {
    my $c = shift;
    my $w;
    $w = AE::timer 3, 0, sub {
      $c->render(text => 'Delayed by 3 seconds!');
      undef $w;
    };
  };

  app->start;

Who actually controls the event loop backend is not important.

  use Mojo::UserAgent;
  use EV;
  use AnyEvent;

  # Search MetaCPAN for "mojolicious"
  my $cv = AE::cv;
  my $ua = Mojo::UserAgent->new;
  $ua->get('api.metacpan.org/v0/module/_search?q=mojolicious' => sub {
    my ($ua, $tx) = @_;
    $cv->send($tx->res->json('/hits/hits/0/_source/release'));
  });
  say $cv->recv;

You could for example just embed the built-in web server into an AnyEvent application.

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

  # Normal action
  get '/' => {text => 'Hello World!'};

  # Connect application with web server and start accepting connections
  my $daemon
    = Mojo::Server::Daemon->new(app => app, listen => ['http://*:8080']);
  $daemon->start;

  # Let AnyEvent take control
  AE::cv->recv;

USER AGENT
When we say Mojolicious is a web framework we actually mean it, with Mojo::UserAgent there's a full featured HTTP and WebSocket user agent built right in.

  Web scraping
Scraping information from web sites has never been this much fun before. The built-in HTML/XML parser Mojo::DOM is accessible through "dom" in Mojo::Message and supports all CSS selectors that make sense for a standalone parser, it can be a very powerful tool especially for testing web application.

  use Mojo::UserAgent;

  # 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 });

  # Visit all nodes recursively to extract more than just text
  for my $n ($tx->res->dom->descendant_nodes->each) {

    # Text or CDATA node
    print $n->content if $n->type eq 'text' || $n->type eq 'cdata';

    # Also include alternate text for images
    print $n->{alt} if $n->type eq 'tag' && $n->tag eq 'img';
  }

For a full list of available CSS selectors see "SELECTORS" in Mojo::DOM::CSS.

  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, it is accessible through "json" in Mojo::Message.

  use Mojo::UserAgent;
  use Mojo::URL;

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

  # Search MetaCPAN for "mojolicious" and list latest releases
  my $url = Mojo::URL->new('http://api.metacpan.org/v0/release/_search');
  $url->query({q => 'mojolicious', sort => 'date:desc'});
  for my $hit (@{$ua->get($url)->res->json->{hits}{hits}}) {
    say "$hit->{_source}{name} ($hit->{_source}{author})";
  }

  Basic authentication
You can just add username and password to the URL, an "Authorization" header will be automatically generated.

  use Mojo::UserAgent;

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

  Decorating follow-up requests
Mojo::UserAgent can automatically follow redirects, the event "start" in Mojo::UserAgent allows you direct access to each transaction right after they have been initialized and before a connection gets associated with them.

  use Mojo::UserAgent;

  # 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.

  Content generators
Content generators can be registered with "add_generator" in Mojo::UserAgent::Transactor to generate the same type of content repeatedly for multiple requests.

  use Mojo::UserAgent;
  use Mojo::Asset::File;

  # Add "stream" generator
  my $ua = Mojo::UserAgent->new;
  $ua->transactor->add_generator(stream => sub {
    my ($transactor, $tx, $path) = @_;
    $tx->req->content->asset(Mojo::Asset::File->new(path => $path));
  });

  # Send multiple files streaming via PUT and POST
  $ua->put('http://example.com/upload'  => stream => '/home/sri/mojo.png');
  $ua->post('http://example.com/upload' => stream => '/home/sri/minion.png');

The "json" and "form" content generators are always available.

  use Mojo::UserAgent;

  # Send "application/json" content via PATCH
  my $ua = Mojo::UserAgent->new;
  my $tx = $ua->patch('http://api.example.com' => json => {foo => 'bar'});

  # Send query parameters via GET
  my $tx2 = $ua->get('http://search.example.com' => form => {q => 'test'});

  # Send "application/x-www-form-urlencoded" content via POST
  my $tx3 = $ua->post('http://search.example.com' => form => {q => 'test'});

  # Send "multipart/form-data" content via PUT
  my $tx4 = $ua->put('http://upload.example.com' =>
    form => {test => {content => 'Hello World!'}});

For more information about available content generators see also "tx" in Mojo::UserAgent::Transactor.

  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, which can then be moved into a permanent file with "move_to" in Mojo::Asset::File.

  use Mojo::UserAgent;

  # Lets fetch the latest Mojolicious tarball
  my $ua = Mojo::UserAgent->new(max_redirects => 5);
  my $tx = $ua->get('https://www.github.com/kraih/mojo/tarball/master');
  $tx->res->content->asset->move_to('mojo.tar.gz');

To protect you from excessively large files there is also a limit of 16MB by default, which you can tweak with the attribute "max_message_size" in Mojo::Message or "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.

  use Mojo::UserAgent;

  # Upload file via POST and "multipart/form-data"
  my $ua = Mojo::UserAgent->new;
  $ua->post('example.com/upload' =>
    form => {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.

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

  use Mojo::UserAgent;

  # Build a normal transaction
  my $ua = Mojo::UserAgent->new;
  my $tx = $ua->build_tx(GET => 'http://example.com');

  # Accept response of indefinite size
  $tx->res->max_message_size(0);

  # Replace "read" events to disable default content parser
  $tx->res->content->unsubscribe('read')->on(read => sub {
    my ($content, $bytes) = @_;
    say "Streaming: $bytes";
  });

  # Process transaction
  $tx = $ua->start($tx);

The event "read" in Mojo::Content will be emitted for every chunk of data that is received, even "chunked" encoding and gzip compression will be handled transparently if necessary.

  Streaming request
Sending a streaming request is almost just as easy.

  use Mojo::UserAgent;

  # Build a normal transaction
  my $ua = Mojo::UserAgent->new;
  my $tx = $ua->build_tx(GET => 'http://example.com');

  # Prepare body
  my $body = 'Hello world!';
  $tx->req->headers->content_length(length $body);

  # Start writing directly with a drain callback
  my $drain;
  $drain = sub {
    my $content = shift;
    my $chunk   = substr $body, 0, 1, '';
    $drain      = undef if $body eq '';
    $content->write($chunk, $drain);
  };
  $tx->req->content->$drain;

  # Process transaction
  $tx = $ua->start($tx);

The drain callback passed to "write" in Mojo::Content will be invoked whenever the entire previous chunk of data has actually been written.

  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 concurrent connections active at the same time.

  use Mojo::UserAgent;
  use Mojo::IOLoop;

  # Concurrent non-blocking requests
  my $ua = Mojo::UserAgent->new;
  $ua->get('http://metacpan.org/search?q=mojo' => sub {
    my ($ua, $mojo) = @_;
    say $mojo->res->dom->at('title')->text;
  });
  $ua->get('http://metacpan.org/search?q=minion' => sub {
    my ($ua, $minion) = @_;
    say $minion->res->dom->at('title')->text;
  });

  # Start event loop if necessary
  Mojo::IOLoop->start unless Mojo::IOLoop->is_running;

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

  Concurrent blocking requests
You can emulate blocking behavior by using "delay" in Mojo::IOLoop to synchronize multiple non-blocking requests.

  use Mojo::UserAgent;
  use Mojo::IOLoop;

  # Synchronize non-blocking requests
  my $ua    = Mojo::UserAgent->new;
  my $delay = Mojo::IOLoop->delay(sub {
    my ($delay, $mojo, $minion) = @_;
    say $mojo->res->dom->at('title')->text;
    say $minion->res->dom->at('title')->text;
  });
  $ua->get('http://metacpan.org/search?q=mojo'   => $delay->begin);
  $ua->get('http://metacpan.org/search?q=minion' => $delay->begin);
  $delay->wait;

The call to "wait" in Mojo::IOLoop::Delay makes this code portable, it can now work inside an already running event loop or start one on demand.

  WebSockets
WebSockets are not just for the server-side, you can use "websocket" in Mojo::UserAgent to open new connections, which are always non-blocking. The WebSocket handshake uses HTTP, and is a normal "GET" request with a few additional headers. It can even contain cookies, and is followed by a 101 response from the server, notifying our user agent that the connection has been established and it can start using the bi-directional WebSocket protocol.

  use Mojo::UserAgent;
  use Mojo::IOLoop;

  # Open WebSocket to echo service
  my $ua = Mojo::UserAgent->new;
  $ua->websocket('ws://echo.websocket.org' => sub {
    my ($ua, $tx) = @_;

    # Check if WebSocket handshake was successful
    say 'WebSocket handshake failed!' and return unless $tx->is_websocket;

    # Wait for WebSocket to be closed
    $tx->on(finish => sub {
      my ($tx, $code, $reason) = @_;
      say "WebSocket closed with status $code.";
    });

    # Close WebSocket after receiving one message
    $tx->on(message => sub {
      my ($tx, $msg) = @_;
      say "WebSocket message: $msg";
      $tx->finish;
    });

    # Send a message to the server
    $tx->send('Hi!');
  });

  # Start event loop if necessary
  Mojo::IOLoop->start unless Mojo::IOLoop->is_running;

  Command line
Don't you hate checking huge HTML files from the command line? Thanks to the command Mojolicious::Command::get that is about to change. You can just pick the parts that actually matter with the CSS selectors from Mojo::DOM and JSON Pointers from Mojo::JSON::Pointer.

  $ 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 -M POST -c 'Hello!' http://mojolicio.us
  $ mojo get -H 'X-Bender: Bite my shiny metal ass!' http://google.com

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

  $ mojo get -r -v http://google.com 'head > title'

Extract just the information you really need from JSON data structures.

  $ mojo get https://api.metacpan.org/v0/author/SRI /name

This can be an invaluable tool for testing your applications.

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

  One-liners
For quick hacks and especially testing, ojo one-liners are also a great choice.

  $ perl -Mojo -E 'say g("mojolicio.us")->dom->at("title")->text'

APPLICATIONS
Fun Mojolicious application hacks for all occasions.

  Basic authentication
Basic authentication data will be automatically extracted from the "Authorization" header.

  use Mojolicious::Lite;

  get '/' => sub {
    my $c = shift;

    # Check for username "Bender" and password "rocks"
    return $c->render(text => 'Hello Bender!')
      if $c->req->url->to_abs->userinfo eq 'Bender:rocks';

    # Require authentication
    $c->res->headers->www_authenticate('Basic');
    $c->render(text => 'Authentication required!', status => 401);
  };

  app->start;

This can be combined with TLS for a secure authentication mechanism.

  $ ./myapp.pl daemon -l 'https://*:3000?cert=./server.crt&key=./server.key'

  Adding a configuration file
Adding a configuration file to your application is as easy as adding a file to its home directory and loading the plugin Mojolicious::Plugin::Config. The default name is based on the value of "moniker" in Mojolicious ("myapp"), appended with a ".conf" extension ("myapp.conf").

  $ mkdir myapp
  $ cd myapp
  $ touch myapp.pl
  $ chmod 744 myapp.pl
  $ echo '{name => "my Mojolicious application"};' > myapp.conf

Configuration files themselves are just Perl scripts that return a hash reference with configuration settings of your choice. All those settings are then available through the method "config" in Mojo and the helper "config" in Mojolicious::Plugin::DefaultHelpers.

  use Mojolicious::Lite;

  plugin 'Config';

  my $name = app->config('name');
  app->log->debug("Welcome to $name");

  get '/' => 'with_config';

  app->start;
  __DATA__
  @@ with_config.html.ep
  <!DOCTYPE html>
  <html>
    <head><title><%= config 'name' %></title></head>
    <body>Welcome to <%= config 'name' %></body>
  </html>

Alternatively you can also use configuration files in the JSON format with Mojolicious::Plugin::JSONConfig.

  Adding a plugin to your application
To organize your code better and to prevent helpers from cluttering your application, you can use application specific plugins.

  $ mkdir -p lib/MyApp/Plugin
  $ touch lib/MyApp/Plugin/MyHelpers.pm

They work just like normal plugins and are also subclasses of Mojolicious::Plugin. Nested helpers with a prefix based on the plugin name are an easy way to avoid conflicts.

  package MyApp::Plugin::MyHelpers;
  use Mojo::Base 'Mojolicious::Plugin';

  sub register {
    my ($self, $app) = @_;
    $app->helper('my_helpers.render_with_header' => sub {
      my ($c, @args) = @_;
      $c->res->headers->header('X-Mojo' => 'I <3 Mojolicious!');
      $c->render(@args);
    });
  }

  1;

You can have as many application specific plugins as you like, the only difference to normal plugins is that you load them using their full class name.

  use Mojolicious::Lite;

  use lib 'lib';

  plugin 'MyApp::Plugin::MyHelpers';

  get '/' => sub {
    my $c = shift;
    $c->my_helpers->render_with_header(text => 'I X Mojolicious!');
  };

  app->start;

Of course these plugins can contain more than just helpers, take a look at "PLUGINS" in Mojolicious::Plugins for a few ideas.

  Adding commands to Mojolicious
By now you've probably 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 'Mojolicious::Command';

  has description => 'Spy on application';
  has usage       => "Usage: APPLICATION spy [TARGET]\n";

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

    # Leak secret passphrases
    say for @{$self->app->secrets} if $args[0] eq 'secrets';

    # Leak mode
    say $self->app->mode if $args[0] eq 'mode';
  }

  1;

Command line arguments are passed right through and there are many useful attributes and methods in Mojolicious::Command that you can use or overload.

  $ mojo spy secrets
  HelloWorld

  $ ./myapp.pl spy secrets
  secr3t

And to make your commands application specific, just add a custom namespace to "namespaces" in Mojolicious::Commands and use a class name like "MyApp::Command::spy" instead of "Mojolicious::Command::spy".

  # Application
  package MyApp;
  use Mojo::Base 'Mojolicious';

  sub startup {
    my $self = shift;

    # Add another namespace to load commands from
    push @{$self->commands->namespaces}, 'MyApp::Command';
  }

  1;

The options "-h"/"--help", "--home" and "-m"/"--mode" are handled automatically by Mojolicious::Commands and are shared by all commands.

  $ ./myapp.pl spy -m production mode
  production

For a full list of shared options see "SYNOPSIS" in Mojolicious::Commands.

  Running code against your application
Ever thought about running a quick one-liner against your Mojolicious application to test something? Thanks to the command Mojolicious::Command::eval you can do just that, the application object itself can be accessed via "app".

  $ mojo generate lite_app myapp.pl
  $ ./myapp.pl eval 'say for @{app->static->paths}'

The "verbose" options will automatically print the return value or returned data structure to "STDOUT".

  $ ./myapp.pl eval -v 'app->static->paths->[0]'
  $ ./myapp.pl eval -V 'app->static->paths'

  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 MyApp
  $ cd my_app
  $ mv public lib/MyApp/
  $ mv templates lib/MyApp/

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

  # Application
  package MyApp;
  use Mojo::Base 'Mojolicious';

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

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

  sub startup {
    my $self = shift;

    # Switch to installable home directory
    $self->home->parse(catdir(dirname(__FILE__), 'MyApp'));

    # Switch to installable "public" directory
    $self->static->paths->[0] = $self->home->rel_dir('public');

    # Switch to installable "templates" directory
    $self->renderer->paths->[0] = $self->home->rel_dir('templates');

    $self->plugin('PODRenderer');

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

  1;

Finally a few small changes should be made to the application script. The shebang becomes the recommended "#!perl", which the toolchain rewrites to the proper shebang during installation. Also use FindBin rather than lib, since installable scripts can't use lib without breaking updated dual-life modules.

  #!perl

  use strict;
  use warnings;

  use FindBin;
  BEGIN { unshift @INC, "$FindBin::Bin/../lib" }

  # Start command line interface for application
  require Mojolicious::Commands;
  Mojolicious::Commands->start_app('MyApp');

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

  $ ./script/my_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 MyApp-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 one-liners
The "Hello World" example above can get even a little bit shorter in an ojo one-liner.

  $ 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 /

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.

SUPPORT
If you have any questions the documentation might not yet answer, don't hesitate to ask on the mailing-list <http://groups.google.com/group/mojolicious> or the official IRC channel "#mojo" on "irc.perl.org".