libmojolicious-perl 2.23-1 / usr / share / perl5 / Mojolicious / Guides / Cookbook.pod

=head1 NAME

Mojolicious::Guides::Cookbook - Cookbook

=head1 OVERVIEW

This document cotains many fun recipes for cooking with L<Mojolicious>.

=head1 DEPLOYMENT

Getting L<Mojolicious> and L<Mojolicious::Lite> applications running on
different platforms.

=head2 Built-in server

L<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.

=head2 Hypnotoad

For bigger applications L<Mojolicious> contains the UNIX optimized preforking
web server L<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 L<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 L<Mojolicious> to automatically pick up the C<X-Forwarded-For>,
C<X-Forwarded-Host> and C<X-Forwarded-HTTPS> headers.

  # hypnotoad.conf
  {proxy => 1};

=head2 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;
    }
  }

=head2 Apache/mod_proxy

Another good reverse proxy is Apache with C<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>

=head2 Apache/CGI

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

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

=head2 PSGI/Plack

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

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

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

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

Because C<plackup> uses a weird trick to load your script, L<Mojolicious> is
not always able to detect the applications home directory, if that's the case
you can simply use the C<MOJO_HOME> environment variable.
Also note that C<app-E<gt>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 C<.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 C<PLACK_ENV> environment
variable.

=head2 Plack middleware

Wrapper scripts like C<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;
  };

=head2 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 C<X-*> headers.
In such cases you can use a C<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';
  });

=head2 Embedding

From time to time you might want to reuse parts of L<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 L<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;

=head1 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 as soon as it is generated, instead of relying on the more
traditional pull model.

=head2 WebSocket

The WebSocket protocol offers full bi-directional low-latency communication
channels between clients and servers.
Receiving messages is as easy as subscribing to the C<message> event of the
transaction, just be aware that all of this is event based, so you should not
block for too long.

  use Mojolicious::Lite;

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

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

    # Connected
    $self->app->log->debug('WebSocket connected.');

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

    # Disconnected
    $self->on(finish => sub {
      my $self = shift;
      $self->app->log->debug('WebSocket disconnected.');
    });
  };

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

The C<finish> event will be emitted right after the WebSocket connection has
been closed.

=head2 Testing WebSockets

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

  use Test::More tests => 4;
  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_message_ok('Hello Mojo!')
    ->message_is('echo: Hello Mojo!')->finish_ok;

=head2 EventSource

HTML5 EventSource is a special form of long-polling where you can 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 $self = shift;

    # Increase connection timeout a bit
    Mojo::IOLoop->connection_timeout($self->tx->connection => 300);

    # Change content type
    $self->res->headers->content_type('text/event-stream');

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

    # Unsubscribe from "message" event again once we are done
    $self->on(finish => sub {
      my $self = shift;
      $self->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 C<message> event will be emitted for every new log message and the
C<finish> event right after the transaction has been finished.

=head1 USER AGENT

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

=head2 Web scraping

Scraping information from web sites has never been this much fun before.
The built-in HTML5/XML parser L<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 L<Mojolicious> applications this can be a
very powerful tool.

=head2 JSON web services

Most web services these days are based on the JSON data-interchange format.
That's why L<Mojolicious> comes with the possibly fastest pure-Perl
implementation L<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;
  }

=head2 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;

=head2 Decorating followup requests

L<Mojo::UserAgent> can automatically follow redirects, the C<start> event
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 C<CONNECT> requests.

=head2 Streaming response

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

  my $ua = Mojo::UserAgent->new;
  my $tx = $ua->build_tx(GET => 'http://mojolicio.us');
  $tx->res->content->on(read => sub {
    my ($content, $chunk) = @_;
    say $chunk;
  });
  $ua->start($tx);

The C<read> event will be emitted for every chunk of data that is received,
even C<chunked> encoding will be handled transparently if necessary.

=head2 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 C<write> will be invoked whenever the entire
previous chunk has actually been written.

=head2 Large file downloads

When downloading large files with L<Mojo::UserAgent> you don't have to worry
about memory usage at all, because it will automatically stream everything
above C<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 limit of C<5MB>
by default, which you can tweak with the C<MOJO_MAX_MESSAGE_SIZE> environment
variable.

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

=head2 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);

=head2 Non-blocking

L<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 reactor
  Mojo::IOLoop->start;

You can take full control of the L<Mojo::IOLoop> reactor.

=head2 Parallel blocking requests

You can emulate blocking behavior by using a L<Mojo::IOLoop> delay to
synchronize multiple non-blocking requests.

  # Synchronize non-blocking requests and capture result
  my $ua    = Mojo::UserAgent->new;
  my $delay = Mojo::IOLoop->delay;
  $ua->get('http://mojolicio.us'         => $delay->begin);
  $ua->get('http://mojolicio.us/perldoc' => $delay->begin);
  my ($tx, $tx2) = $delay->wait;

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

=head2 Command line

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

=head1 HACKS

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

=head2 Faster tests

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

  $ HARNESS_OPTIONS=j5 make test
  ...

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

=head2 Adding commands to Mojolicious

By now you've propably used many of the built-in commands described in
L<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 L<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".

=head2 Running code against your application

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

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

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

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

=head2 Making your application installable

Ever thought about releasing your L<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 C<public> and C<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 C<PAUSE> account (which can be requested at
L<http://pause.perl.org>) even upload it.

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

=head2 Hello World

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

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

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

=head2 Hello World oneliner

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

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

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

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

=head1 MORE

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

=cut