1Mojolicious::Guides::CoUoskebrooCko(n3t)ributed Perl DocMuomjeonltiactiioouns::Guides::Cookbook(3)
2
6 Mojolicious::Guides::Cookbook - Cooking with Mojolicious
7
9 This document contains many fun recipes for cooking with Mojolicious.
10
12 Essentials every Mojolicious developer should know.
13 Blocking and non-blocking operations
15 A blocking operation is a subroutine that blocks the execution of the
16 calling subroutine until the subroutine is finished.
17 sub foo {
19 my $result = blocking_subroutine();
20 ...
21 }
22 A non-blocking operation on the other hand lets the calling subroutine
24 continue execution even though the subroutine is not yet finished.
25 Instead of waiting, the calling subroutine passes along a callback to
26 be executed once the subroutine is finished, this is called
27 continuation-passing style.
28 sub foo {
30 non_blocking_subroutine(sub ($result) {
31 ...
32 });
33 ...
34 }
35 While Mojolicious has been designed from the ground up for non-blocking
37 I/O and event loops, it is not possible to magically make Perl code
38 non-blocking. You have to use specialized non-blocking code available
39 through modules like Mojo::IOLoop and Mojo::UserAgent, or third-party
40 event loops. You can wrap your blocking code in subprocesses though to
41 prevent it from interfering with your non-blocking code.
42 Event loops
44 An event loop is basically a loop that continually tests for external
45 events and executes the appropriate callbacks to handle them, it is
46 often the main loop in a program. Non-blocking tests for
47 readability/writability of file descriptors and timers are commonly
48 used events for highly scalable network servers, because they allow a
49 single process to handle thousands of client connections concurrently.
50 while (1) {
52 my @readable = test_fds_for_readability();
53 handle_readable_fds(@readable);
54 my @writable = test_fds_for_writability();
56 handle_writable_fds(@writable);
57 my @expired = test_timers();
59 handle_timers(@expired);
60 }
61 In Mojolicious this event loop is Mojo::IOLoop.
63 Reverse proxy
65 A reverse proxy architecture is a deployment technique used in many
66 production environments, where a reverse proxy server is put in front
67 of your application to act as the endpoint accessible by external
68 clients. It can provide a lot of benefits, like terminating SSL
69 connections from the outside, limiting the number of concurrent open
70 sockets towards the Mojolicious application (or even using Unix
71 sockets), balancing load across multiple instances, or supporting
72 several applications through the same IP/port.
73 ..........................................
75 : :
76 +--------+ : +-----------+ +---------------+ :
77 | |-------->| | | | :
78 | client | : | reverse |----->| Mojolicious | :
79 | |<--------| proxy | | application | :
80 +--------+ : | |<-----| | :
81 : +-----------+ +---------------+ :
82 : :
83 .. system boundary (e.g. same host) ......
84 This setup introduces some problems, though: the application will
86 receive requests from the reverse proxy instead of the original client;
87 the address/hostname where your application lives internally will be
88 different from the one visible from the outside; and if terminating
89 SSL, the reverse proxy exposes services via HTTPS while using HTTP
90 towards the Mojolicious application.
91 As an example, compare a sample request from the client and what the
93 Mojolicious application receives:
94 client reverse proxy Mojolicious app
96 __|__ _______________|______________ ____|____
97 / \ / \ / \
98 1.2.3.4 --HTTPS--> api.example.com 10.20.30.39 --HTTP--> 10.20.30.40
99 GET /foo/1 HTTP/1.1 | GET /foo/1 HTTP/1.1
101 Host: api.example.com | Host: 10.20.30.40
102 User-Agent: Firefox | User-Agent: ShinyProxy/1.2
103 ... | ...
104 However, now the client address is no longer available (which might be
106 useful for analytics, or Geo-IP) and URLs generated via "url_for" in
107 Mojolicious::Controller will look like this:
108 http://10.20.30.40/bar/2
110 instead of something meaningful for the client, like this:
112 https://api.example.com/bar/2
114 To solve these problems, you can configure your reverse proxy to send
116 the missing data (see "Nginx" and "Apache/mod_proxy") and tell your
117 application about it by setting the environment variable
118 "MOJO_REVERSE_PROXY". In more complex situations, usually involving
119 multiple proxies or proxies that live outside your network, it can be
120 necessary to tell the application from which ip addresses to expect
121 proxy requests by setting "MOJO_TRUSTED_PROXIES" to a list of comma
122 separated addresses or CIDR networks. For even finer control,
123 "Rewriting" includes examples of how the changes could be implemented
124 manually.
125
127 Getting Mojolicious and Mojolicious::Lite applications running on
128 different platforms. Note that many real-time web features are based on
129 the Mojo::IOLoop event loop, and therefore require one of the built-in
130 web servers to be able to use them to their full potential.
131 Built-in web server
133 Mojolicious contains a very portable non-blocking I/O HTTP and
134 WebSocket server with Mojo::Server::Daemon. It is usually used during
135 development and in the construction of more advanced web servers, but
136 is solid and fast enough for small to mid sized applications.
137 $ ./script/my_app daemon
139 Web application available at http://127.0.0.1:3000
140 It is available to every application through the command
142 Mojolicious::Command::daemon, which has many configuration options and
143 is known to work on every platform Perl works on with its single-
144 process architecture.
145 $ ./script/my_app daemon -h
147 ...List of available options...
148 Another huge advantage is that it supports TLS and WebSockets out of
150 the box, a development certificate for testing purposes is built right
151 in, so it just works, but you can specify all listen locations
152 supported by "listen" in Mojo::Server::Daemon.
153 $ ./script/my_app daemon -l https://[::]:3000
155 Web application available at https://[::]:3000
156 To manage the web server with systemd, you can use a unit configuration
158 file like this.
159 [Unit]
161 Description=My Mojolicious application
162 After=network.target
163 [Service]
165 Type=simple
166 User=sri
167 ExecStart=/home/sri/myapp/script/my_app daemon -m production -l http://*:8080
168 [Install]
170 WantedBy=multi-user.target
171 Pre-forking
173 For bigger applications Mojolicious contains the UNIX optimized pre-
174 forking web server Mojo::Server::Prefork, which can take advantage of
175 multiple CPU cores and copy-on-write memory management to scale up to
176 thousands of concurrent client connections.
177 Mojo::Server::Prefork
179 |- Mojo::Server::Daemon [1]
180 |- Mojo::Server::Daemon [2]
181 |- Mojo::Server::Daemon [3]
182 +- Mojo::Server::Daemon [4]
183 It is based on Mojo::Server::Daemon and available to every application
185 through the command Mojolicious::Command::prefork.
186 $ ./script/my_app prefork
188 Web application available at http://127.0.0.1:3000
189 Since all built-in web servers are based on the Mojo::IOLoop event
191 loop, they scale best with non-blocking operations. But if your
192 application for some reason needs to perform many blocking operations,
193 you can improve performance by increasing the number of worker
194 processes and decreasing the number of concurrent connections each
195 worker is allowed to handle (often as low as 1).
196 $ ./script/my_app prefork -m production -w 10 -c 1
198 Web application available at http://127.0.0.1:3000
199 During startup your application is preloaded in the manager process,
201 which does not run an event loop, so you can use "next_tick" in
202 Mojo::IOLoop to run code whenever a new worker process has been forked
203 and its event loop gets started.
204 use Mojolicious::Lite;
206 Mojo::IOLoop->next_tick(sub ($ioloop) {
208 app->log->info("Worker $$ star...ALL GLORY TO THE HYPNOTOAD!");
209 });
210 get '/' => {text => 'Hello Wor...ALL GLORY TO THE HYPNOTOAD!'};
212 app->start;
214 And to manage the pre-forking web server with systemd, you can use a
216 unit configuration file like this.
217 [Unit]
219 Description=My Mojolicious application
220 After=network.target
221 [Service]
223 Type=simple
224 User=sri
225 ExecStart=/home/sri/myapp/script/my_app prefork -m production -l http://*:8080
226 [Install]
228 WantedBy=multi-user.target
229 Morbo
231 After reading the Mojolicious::Guides::Tutorial, you should already be
232 familiar with Mojo::Server::Morbo.
233 Mojo::Server::Morbo
235 +- Mojo::Server::Daemon
236 It is basically a restarter that forks a new Mojo::Server::Daemon web
238 server whenever a file in your project changes, and should therefore
239 only be used during development. To start applications with it you can
240 use the morbo script.
241 $ morbo ./script/my_app
243 Web application available at http://127.0.0.1:3000
244 Containers
246 There are many ways to go cloud-native with Mojolicious. To get you
247 started with containerizing your web applications we will explore one
248 of them in this recipe. First, you will need to declare the CPAN
249 dependencies of your application, for example in a "Makefile.PL" file.
250 This should always include at the very least Mojolicious itself.
251 use strict;
253 use warnings;
254 use ExtUtils::MakeMaker;
256 WriteMakefile(
258 VERSION => '0.01',
259 PREREQ_PM => {
260 'Mojolicious' => '8.65',
261 'Mojolicious::Plugin::Status' => '1.12'
262 },
263 test => {TESTS => 't/*.t'}
264 );
265 The helper command Mojolicious::Command::Author::generate::makefile can
267 also generate a minimal "Makefile.PL" for you.
268 $ ./myapp.pl generate makefile
270 ...
271 And then we are going to need a "Dockerfile" describing the container.
273 A very simple one will do for now.
274 FROM perl
276 WORKDIR /opt/myapp
277 COPY . .
278 RUN cpanm --installdeps -n .
279 EXPOSE 3000
280 CMD ./myapp.pl prefork
281 It uses the latest Perl container <https://hub.docker.com/_/perl> from
283 Docker Hub, copies all the contents of your application directory into
284 the container, installs CPAN dependencies with App::cpanminus, and then
285 starts the application on port 3000 with the pre-forking web server.
286 With Mojolicious::Command::Author::generate::dockerfile there is also a
287 helper command to generate a minimal "Dockerfile" for you.
288 $ ./myapp.pl generate dockerfile
290 ...
291 To build and deploy our container there are also many options
293 available, here we will simply use Docker.
294 $ docker build -t myapp_image .
296 ...
297 $ docker run -d -p 3000:3000 --name myapp_container myapp_image
298 ...
299 And now your web application should be deployed as a container under
301 "http://127.0.0.1:3000". For more information and many more container
302 deployment options we recommend the Docker <https://docs.docker.com/>
303 and Kubernetes <https://kubernetes.io/docs/> documentation.
304 Hypnotoad
306 Hypnotoad is based on the Mojo::Server::Prefork web server, and adds
307 some features especially optimized for high availability non-
308 containerized production environments. To start applications with it
309 you can use the hypnotoad script, which listens on port 8080,
310 automatically daemonizes the server process and defaults to
311 "production" mode for Mojolicious and Mojolicious::Lite applications.
312 $ hypnotoad ./script/my_app
314 Many configuration settings can be tweaked right from within your
316 application with "config" in Mojolicious, for a full list see
317 "SETTINGS" in Mojo::Server::Hypnotoad.
318 use Mojolicious::Lite;
320 app->config(hypnotoad => {listen => ['http://*:80']});
322 get '/' => {text => 'Hello Wor...ALL GLORY TO THE HYPNOTOAD!'};
324 app->start;
326 Or just add a "hypnotoad" section to your Mojolicious::Plugin::Config,
328 Mojolicious::Plugin::JSONConfig or Mojolicious::Plugin::NotYAMLConfig
329 configuration file.
330 # myapp.conf
332 {
333 hypnotoad => {
334 listen => ['https://*:443?cert=/etc/server.crt&key=/etc/server.key'],
335 workers => 10
336 }
337 };
338 But one of its biggest advantages is the support for effortless zero
340 downtime software upgrades (hot deployment). That means you can upgrade
341 Mojolicious, Perl or even system libraries at runtime without ever
342 stopping the server or losing a single incoming connection, just by
343 running the command above again.
344 $ hypnotoad ./script/my_app
346 Starting hot deployment for Hypnotoad server 31841.
347 You might also want to enable proxy support if you're using Hypnotoad
349 behind a reverse proxy. This allows Mojolicious to automatically pick
350 up the "X-Forwarded-For" and "X-Forwarded-Proto" headers.
351 # myapp.conf
353 {hypnotoad => {proxy => 1}};
354 To manage Hypnotoad with systemd, you can use a unit configuration file
356 like this.
357 [Unit]
359 Description=My Mojolicious application
360 After=network.target
361 [Service]
363 Type=forking
364 User=sri
365 PIDFile=/home/sri/myapp/script/hypnotoad.pid
366 ExecStart=/path/to/hypnotoad /home/sri/myapp/script/my_app
367 ExecReload=/path/to/hypnotoad /home/sri/myapp/script/my_app
368 KillMode=process
369 [Install]
371 WantedBy=multi-user.target
372 Zero downtime software upgrades
374 Hypnotoad makes zero downtime software upgrades (hot deployment) very
375 simple, as you can see above, but on modern operating systems that
376 support the "SO_REUSEPORT" socket option, there is also another method
377 available that works with all built-in web servers.
378 $ ./script/my_app prefork -P /tmp/first.pid -l http://*:8080?reuse=1
380 Web application available at http://127.0.0.1:8080
381 All you have to do, is to start a second web server listening to the
383 same port, and stop the first web server gracefully afterwards.
384 $ ./script/my_app prefork -P /tmp/second.pid -l http://*:8080?reuse=1
386 Web application available at http://127.0.0.1:8080
387 $ kill -s TERM `cat /tmp/first.pid`
388 Just remember that both web servers need to be started with the "reuse"
390 parameter.
391 Nginx
393 One of the most popular setups these days is Hypnotoad behind an Nginx
394 <https://nginx.org> reverse proxy, which even supports WebSockets in
395 newer versions.
396 upstream myapp {
398 server 127.0.0.1:8080;
399 }
400 server {
401 listen 80;
402 server_name localhost;
403 location / {
404 proxy_pass http://myapp;
405 proxy_http_version 1.1;
406 proxy_set_header Upgrade $http_upgrade;
407 proxy_set_header Connection "upgrade";
408 proxy_set_header Host $host;
409 proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
410 proxy_set_header X-Forwarded-Proto $scheme;
411 }
412 }
413 Apache/mod_proxy
415 Another good reverse proxy is Apache <https://httpd.apache.org> with
416 "mod_proxy", the configuration looks quite similar to the Nginx one
417 above. And if you need WebSocket support, newer versions come with
418 "mod_proxy_wstunnel".
419 <VirtualHost *:80>
421 ServerName localhost
422 <Proxy *>
423 Require all granted
424 </Proxy>
425 ProxyRequests Off
426 ProxyPreserveHost On
427 ProxyPass /echo ws://localhost:8080/echo
428 ProxyPass / http://localhost:8080/ keepalive=On
429 ProxyPassReverse / http://localhost:8080/
430 RequestHeader set X-Forwarded-Proto "http"
431 </VirtualHost>
432 Apache/CGI
434 "CGI" is supported out of the box and your Mojolicious application will
435 automatically detect that it is executed as a "CGI" script. Its use in
436 production environments is discouraged though, because as a result of
437 how "CGI" works, it is very slow and many web servers are making it
438 exceptionally hard to configure properly. Additionally, many real-time
439 web features, such as WebSockets, are not available.
440 ScriptAlias / /home/sri/my_app/script/my_app/
442 Envoy
444 Mojolicious applications can be deployed on cloud-native environments
445 that use Envoy <https://www.envoyproxy.io>, such as with this reverse
446 proxy configuration similar to the Apache and Nginx ones above.
447 static_resources:
449 listeners:
450 - name: listener_0
451 address:
452 socket_address: { address: 0.0.0.0, port_value: 80 }
453 filter_chains:
454 - filters:
455 - name: envoy.filters.network.http_connection_manager
456 typed_config:
457 "@type": type.googleapis.com/envoy.extensions.filters.network.http_connection_manager.v3.HttpConnectionManager
458 codec_type: auto
459 stat_prefix: index_http
460 route_config:
461 name: local_route
462 virtual_hosts:
463 - name: service
464 domains: ["*"]
465 routes:
466 - match:
467 prefix: "/"
468 route:
469 cluster: local_service
470 upgrade_configs:
471 - upgrade_type: websocket
472 http_filters:
473 - name: envoy.filters.http.router
474 typed_config:
475 clusters:
476 - name: local_service
477 connect_timeout: 0.25s
478 type: strict_dns
479 lb_policy: round_robin
480 load_assignment:
481 cluster_name: local_service
482 endpoints:
483 - lb_endpoints:
484 - endpoint:
485 address:
486 socket_address: { address: mojo, port_value: 8080 }
487 While this configuration works for simple applications, Envoy's typical
489 use case is for implementing proxies of applications as a "service
490 mesh" providing advanced filtering, load balancing, and observability
491 features, such as seen in Istio
492 <https://istio.io/latest/docs/ops/deployment/architecture/>. For more
493 examples, visit the Envoy documentation
494 <https://www.envoyproxy.io/docs/envoy/latest/start/start>.
495 PSGI/Plack
497 PSGI is an interface between Perl web frameworks and web servers, and
498 Plack is a Perl module and toolkit that contains PSGI middleware,
499 helpers and adapters to web servers. PSGI and Plack are inspired by
500 Python's WSGI and Ruby's Rack. Mojolicious applications are
501 ridiculously simple to deploy with Plack, but be aware that many real-
502 time web features, such as WebSockets, are not available.
503 $ plackup ./script/my_app
505 Plack provides many server and protocol adapters for you to choose
507 from, such as "FCGI", "uWSGI" and "mod_perl".
508 $ plackup ./script/my_app -s FCGI -l /tmp/myapp.sock
510 The "MOJO_REVERSE_PROXY" environment variable can be used to enable
512 proxy support, this allows Mojolicious to automatically pick up the
513 "X-Forwarded-For" and "X-Forwarded-Proto" headers.
514 $ MOJO_REVERSE_PROXY=1 plackup ./script/my_app
516 If an older server adapter is unable to correctly detect the
518 application home directory, you can simply use the "MOJO_HOME"
519 environment variable.
520 $ MOJO_HOME=/home/sri/my_app plackup ./script/my_app
522 There is no need for a ".psgi" file, just point the server adapter at
524 your application script, it will automatically act like one if it
525 detects the presence of a "PLACK_ENV" environment variable.
526 Plack middleware
528 Wrapper scripts like "myapp.fcgi" are a great way to separate
529 deployment and application logic.
530 #!/usr/bin/env plackup -s FCGI
532 use Plack::Builder;
533 builder {
535 enable 'Deflater';
536 require './script/my_app';
537 };
538 Mojo::Server::PSGI can be used directly to load and customize
540 applications in the wrapper script.
541 #!/usr/bin/env plackup -s FCGI
543 use Mojo::Server::PSGI;
544 use Plack::Builder;
545 builder {
547 enable 'Deflater';
548 my $server = Mojo::Server::PSGI->new;
549 $server->load_app('./script/my_app');
550 $server->app->config(foo => 'bar');
551 $server->to_psgi_app;
552 };
553 But you could even use middleware right in your application.
555 use Mojolicious::Lite -signatures;
557 use Plack::Builder;
558 get '/welcome' => sub ($c) {
560 $c->render(text => 'Hello Mojo!');
561 };
562 builder {
564 enable 'Deflater';
565 app->start;
566 };
567 Rewriting
569 Sometimes you might have to deploy your application in a blackbox
570 environment where you can't just change the server configuration or
571 behind a reverse proxy that passes along additional information with
572 "X-Forwarded-*" headers. In such cases you can use the hook
573 "before_dispatch" in Mojolicious to rewrite incoming requests.
574 # Change scheme if "X-Forwarded-HTTPS" header is set
576 $app->hook(before_dispatch => sub ($c) {
577 $c->req->url->base->scheme('https')
578 if $c->req->headers->header('X-Forwarded-HTTPS');
579 });
580 Since reverse proxies generally don't pass along information about path
582 prefixes your application might be deployed under, rewriting the base
583 path of incoming requests is also quite common. This allows "url_for"
584 in Mojolicious::Controller for example, to generate portable URLs based
585 on the current environment.
586 # Move first part and slash from path to base path in production mode
588 $app->hook(before_dispatch => sub ($c) {
589 push @{$c->req->url->base->path->trailing_slash(1)},
590 shift @{$c->req->url->path->leading_slash(0)};
591 }) if $app->mode eq 'production';
592 Mojo::URL objects are very easy to manipulate, just make sure that the
594 URL ("foo/bar?baz=yada"), which represents the routing destination, is
595 always relative to the base URL ("http://example.com/myapp/"), which
596 represents the deployment location of your application.
597 Deployment specific plugins
599 Deployment specific 3rd party plugins such as
600 Mojolicious::Plugin::SetUserGroup do not need to be included in your
601 application code. They can also be loaded later on via the reserved
602 "plugins" value for Mojolicious applications that are using any one of
603 the built-in configuration plugins Mojolicious::Plugin::Config,
604 Mojolicious::Plugin::JSONConfig or Mojolicious::Plugin::NotYAMLConfig.
605 # myapp.conf
607 {
608 plugins => [
609 {SetUserGroup => {user => 'sri', group => 'staff'}}
610 ]
611 };
612 Application embedding
614 From time to time you might want to reuse parts of Mojolicious
615 applications like configuration files, database connection or helpers
616 for other scripts, with this little Mojo::Server based mock server you
617 can just embed them.
618 use Mojo::Server;
620 # Load application with mock server
622 my $server = Mojo::Server->new;
623 my $app = $server->load_app('./myapp.pl');
624 # Access fully initialized application
626 say for @{$app->static->paths};
627 say $app->config->{secret_identity};
628 say $app->dumper({just => 'a helper test'});
629 say $app->build_controller->render_to_string(template => 'foo');
630 The plugin Mojolicious::Plugin::Mount uses this functionality to allow
632 you to combine multiple applications into one and deploy them together.
633 use Mojolicious::Lite;
635 app->config(hypnotoad => {listen => ['http://*:80']});
637 plugin Mount => {'test1.example.com' => '/home/sri/myapp1.pl'};
639 plugin Mount => {'test2.example.com' => '/home/sri/myapp2.pl'};
640 app->start;
642 Web server embedding
644 You can also use "one_tick" in Mojo::IOLoop to embed the built-in web
645 server Mojo::Server::Daemon into alien environments like foreign event
646 loops that for some reason can't just be integrated with a new reactor
647 backend.
648 use Mojolicious::Lite;
650 use Mojo::IOLoop;
651 use Mojo::Server::Daemon;
652 # Normal action
654 get '/' => {text => 'Hello World!'};
655 # Connect application with web server and start accepting connections
657 my $daemon = Mojo::Server::Daemon->new(app => app, listen => ['http://*:8080']);
658 $daemon->start;
659 # Call "one_tick" repeatedly from the alien environment
661 Mojo::IOLoop->one_tick while 1;
662
664 The real-time web is a collection of technologies that include Comet
665 (long polling), EventSource and WebSockets, which allow content to be
666 pushed to consumers with long-lived connections as soon as it is
667 generated, instead of relying on the more traditional pull model. All
668 built-in web servers use non-blocking I/O and are based on the
669 Mojo::IOLoop event loop, which provides many very powerful features
670 that allow real-time web applications to scale up to thousands of
671 concurrent client connections.
672 Backend web services
674 Since Mojo::UserAgent is also based on the Mojo::IOLoop event loop, it
675 won't block the built-in web servers when used non-blocking, even for
676 high latency backend web services.
677 use Mojolicious::Lite -signatures;
679 # Search MetaCPAN for "mojolicious"
681 get '/' => sub ($c) {
682 $c->ua->get('fastapi.metacpan.org/v1/module/_search?q=mojolicious' => sub ($ua, $tx) {
683 $c->render('metacpan', hits => $tx->result->json->{hits}{hits});
684 });
685 };
686 app->start;
688 __DATA__
689 @@ metacpan.html.ep
691 <!DOCTYPE html>
692 <html>
693 <head><title>MetaCPAN results for "mojolicious"</title></head>
694 <body>
695 % for my $hit (@$hits) {
696 <p><%= $hit->{_source}{release} %></p>
697 % }
698 </body>
699 </html>
700 The callback passed to "get" in Mojo::UserAgent will be executed once
702 the request to the backend web service has been finished, this is
703 called continuation-passing style.
704 Synchronizing non-blocking operations
706 Multiple non-blocking operations, such as concurrent requests, can be
707 easily synchronized with promises and "all" in Mojo::Promise. You
708 create Mojo::Promise objects manually or use methods like "get_p" in
709 Mojo::UserAgent that create them for you.
710 use Mojolicious::Lite -signatures;
712 use Mojo::Promise;
713 use Mojo::URL;
714 # Search MetaCPAN for "mojo" and "minion"
716 get '/' => sub ($c) {
717 # Create two promises
719 my $url = Mojo::URL->new('http://fastapi.metacpan.org/v1/module/_search');
720 my $mojo = $c->ua->get_p($url->clone->query({q => 'mojo'}));
721 my $minion = $c->ua->get_p($url->clone->query({q => 'minion'}));
722 # Render a response once both promises have been resolved
724 Mojo::Promise->all($mojo, $minion)->then(sub ($mojo, $minion) {
725 $c->render(json => {
726 mojo => $mojo->[0]->result->json('/hits/hits/0/_source/release'),
727 minion => $minion->[0]->result->json('/hits/hits/0/_source/release')
728 });
729 })->catch(sub ($err) {
730 $c->reply->exception($err);
731 })->wait;
732 };
733 app->start;
735 To create promises manually you just wrap your continuation-passing
737 style APIs in functions that return promises. Here's an example for
738 how "get_p" in Mojo::UserAgent works internally.
739 use Mojo::UserAgent;
741 use Mojo::Promise;
742 # Wrap a user agent method with a promise
744 my $ua = Mojo::UserAgent->new;
745 sub get_p {
746 my $promise = Mojo::Promise->new;
747 $ua->get(@_ => sub ($ua, $tx) {
748 my $err = $tx->error;
749 $promise->resolve($tx) if !$err || $err->{code};
750 $promise->reject($err->{message});
751 });
752 return $promise;
753 }
754 # Use our new promise generating function
756 get_p('https://mojolicious.org')->then(sub ($tx) {
757 say $tx->result->dom->at('title')->text;
758 })->wait;
759 Promises have three states, they start out as "pending" and you call
761 "resolve" in Mojo::Promise to transition them to "fulfilled", or
762 "reject" in Mojo::Promise to transition them to "rejected".
763 async/await
765 And if you have Future::AsyncAwait installed you can make using
766 promises even easier. The "async" and "await" keywords are enabled with
767 the "-async_await" flag of Mojo::Base, and make the use of closures
768 with promises completely optional.
769 use Mojo::Base -strict, -async_await;
771 The "async" keyword is placed before the "sub" keyword, and means that
773 this function always returns a promise. Returned values that are not
774 Mojo::Promise objects will be wrapped in a resolved promise
775 automatically. And if an exception gets thrown in the function it will
776 result in a rejected promise.
777 use Mojo::Base -strict, -async_await;
779 async sub hello_p {
781 return 'Hello Mojo!';
782 }
783 hello_p()->then(sub { say @_ })->wait;
785 The "await" keyword on the other hand makes Perl wait for the promise
787 to be settled. It then returns the fulfillment values or throws an
788 exception with the rejection reason. While waiting, the event loop is
789 free to perform other tasks however, so no resources are wasted.
790 use Mojo::Base -strict, -signatures, -async_await;
792 use Mojo::UserAgent;
793 use Mojo::URL;
794 my $ua = Mojo::UserAgent->new;
796 # Search MetaCPAN non-blocking for multiple terms sequentially
798 async sub search_cpan_p ($terms) {
799 my $cpan = Mojo::URL->new('http://fastapi.metacpan.org/v1/module/_search');
800 my @urls = map { $cpan->clone->query(q => $_) } @$terms;
801 for my $url (@urls) {
803 my $tx = await $ua->get_p($url);
804 say $tx->result->json('/hits/hits/0/_source/release');
805 }
806 }
807 search_cpan_p(['mojo', 'minion'])->wait;
809 The loop above performs all requests sequentially, awaiting a result
811 before sending the next request. But you can also perform those
812 requests concurrently instead, by using methods like "all" in
813 Mojo::Promise to combine multiple promises before awaiting the results.
814 use Mojo::Base -strict, -signatures, -async_await;
816 use Mojo::Promise;
817 use Mojo::UserAgent;
818 use Mojo::URL;
819 my $ua = Mojo::UserAgent->new;
821 # Search MetaCPAN non-blocking for multiple terms concurrently
823 async sub search_cpan_p ($terms) {
824 my $cpan = Mojo::URL->new('http://fastapi.metacpan.org/v1/module/_search');
825 my @urls = map { $cpan->clone->query(q => $_) } @$terms;
826 my @promises = map { $ua->get_p($_) } @urls;
828 my @results = await Mojo::Promise->all(@promises);
829 for my $result (@results) {
830 say $result->[0]->result->json('/hits/hits/0/_source/release');
831 }
832 }
833 search_cpan_p(['mojo', 'minion'])->wait;
835 All of this also means that you can use normal Perl exception handling
837 again. Even many 3rd party exception handling modules from CPAN work
838 just fine.
839 use Mojo::Base -strict, -async_await;
841 use Mojo::Promise;
842 # Catch a non-blocking exception
844 async sub hello_p {
845 eval { await Mojo::Promise->reject('This is an exception') };
846 if (my $err = $@) { warn "Error: $err" }
847 }
848 hello_p()->wait;
850 And it works just the same in Mojolicious and Mojolicious::Lite
852 applications. Just declare your actions with the "async" keyword and
853 use "await" to wait for promises to be "fulfilled" or "rejected".
854 use Mojolicious::Lite -signatures, -async_await;
856 # Request HTML titles from two sites non-blocking
858 get '/' => async sub ($c) {
859 my $mojo_tx = await $c->ua->get_p('https://mojolicious.org');
860 my $mojo_title = $mojo_tx->result->dom->at('title')->text;
861 my $cpan_tx = await $c->ua->get_p('https://metacpan.org');
862 my $cpan_title = $cpan_tx->result->dom->at('title')->text;
863 $c->render(json => {mojo => $mojo_title, cpan => $cpan_title});
865 };
866 app->start;
868 Promises returned by actions will automatically get the default
870 Mojolicious exception handler attached. Making it much harder to ever
871 miss a non-blocking exception again, even if you forgot to handle it
872 yourself.
873 Timers
875 Timers, another primary feature of the event loop, are created with
876 "timer" in Mojo::IOLoop and can, for example, be used to delay
877 rendering of a response, and unlike "sleep", won't block any other
878 requests that might be processed concurrently.
879 use Mojolicious::Lite -signatures;
881 use Mojo::IOLoop;
882 # Wait 3 seconds before rendering a response
884 get '/' => sub ($c) {
885 Mojo::IOLoop->timer(3 => sub ($ioloop) {
886 $c->render(text => 'Delayed by 3 seconds!');
887 });
888 };
889 app->start;
891 Recurring timers created with "recurring" in Mojo::IOLoop are slightly
893 more powerful, but need to be stopped manually, or they would just keep
894 getting emitted.
895 use Mojolicious::Lite -signatures;
897 use Mojo::IOLoop;
898 # Count to 5 in 1 second steps
900 get '/' => sub ($c) {
901 # Start recurring timer
903 my $i = 1;
904 my $id = Mojo::IOLoop->recurring(1 => sub ($ioloop) {
905 $c->write_chunk($i);
906 $c->finish if $i++ == 5;
907 });
908 # Stop recurring timer
910 $c->on(finish => sub ($c) { Mojo::IOLoop->remove($id) });
911 };
912 app->start;
914 Timers are not tied to a specific request or connection, and can even
916 be created at startup time.
917 use Mojolicious::Lite -signatures;
919 use Mojo::IOLoop;
920 # Check title in the background every 10 seconds
922 my $title = 'Got no title yet.';
923 Mojo::IOLoop->recurring(10 => sub ($ioloop) {
924 app->ua->get('https://mojolicious.org' => sub ($ua, $tx) {
925 $title = $tx->result->dom->at('title')->text;
926 });
927 });
928 # Show current title
930 get '/' => sub ($c) {
931 $c->render(json => {title => $title});
932 };
933 app->start;
935 Just remember that all these non-blocking operations are processed
937 cooperatively, so your callbacks shouldn't block for too long.
938 Subprocesses
940 You can also use subprocesses, created with "subprocess" in
941 Mojo::IOLoop, to perform computationally expensive operations without
942 blocking the event loop.
943 use Mojolicious::Lite -signatures;
945 use Mojo::IOLoop;
946 # Operation that would block the event loop for 5 seconds
948 get '/' => sub ($c) {
949 Mojo::IOLoop->subprocess->run_p(sub {
950 sleep 5;
951 return '♥', 'Mojolicious';
952 })->then(sub (@results) {
953 $c->render(text => "I $results[0] $results[1]!");
954 })->catch(sub ($err) {
955 $c->reply->exception($err);
956 });
957 };
958 app->start;
960 The callback passed to "run_p" in Mojo::IOLoop::Subprocess will be
962 executed in a child process, without blocking the event loop of the
963 parent process. The results of the callback will then be shared between
964 both processes, and the promise fulfilled or rejected in the parent
965 process.
966 Exceptions in non-blocking operations
968 Since timers and other non-blocking operations are running solely in
969 the event loop, outside of the application, exceptions that get thrown
970 in callbacks can't get caught and handled automatically. But you can
971 handle them manually by subscribing to the event "error" in
972 Mojo::Reactor or catching them inside the callback.
973 use Mojolicious::Lite -signatures;
975 use Mojo::IOLoop;
976 # Forward error messages to the application log
978 Mojo::IOLoop->singleton->reactor->on(error => sub ($reactor, $err) {
979 app->log->error($err);
980 });
981 # Exception only gets logged (and connection times out)
983 get '/connection_times_out' => sub ($c) {
984 Mojo::IOLoop->timer(2 => sub ($ioloop) {
985 die 'This request will not be getting a response';
986 });
987 };
988 # Exception gets caught and handled
990 get '/catch_exception' => sub ($c) {
991 Mojo::IOLoop->timer(2 => sub ($ioloop) {
992 eval { die 'This request will be getting a response' };
993 $c->reply->exception($@) if $@;
994 });
995 };
996 app->start;
998 A default subscriber that turns all errors into warnings will usually
1000 be added by Mojo::IOLoop as a fallback.
1001 Mojo::IOLoop->singleton->reactor->unsubscribe('error');
1003 During development or for applications where crashing is simply
1005 preferable, you can also make every exception that gets thrown in a
1006 callback fatal by removing all of its subscribers.
1007 WebSocket web service
1009 The WebSocket protocol offers full bi-directional low-latency
1010 communication channels between clients and servers. Receive messages
1011 just by subscribing to events such as "message" in
1012 Mojo::Transaction::WebSocket with "on" in Mojolicious::Controller and
1013 return them with "send" in Mojolicious::Controller.
1014 use Mojolicious::Lite -signatures;
1016 # Template with browser-side code
1018 get '/' => 'index';
1019 # WebSocket echo service
1021 websocket '/echo' => sub ($c) {
1022 # Opened
1024 $c->app->log->debug('WebSocket opened');
1025 # Increase inactivity timeout for connection a bit
1027 $c->inactivity_timeout(300);
1028 # Incoming message
1030 $c->on(message => sub ($c, $msg) {
1031 $c->send("echo: $msg");
1032 });
1033 # Closed
1035 $c->on(finish => sub ($c, $code, $reason = undef) {
1036 $c->app->log->debug("WebSocket closed with status $code");
1037 });
1038 };
1039 app->start;
1041 __DATA__
1042 @@ index.html.ep
1044 <!DOCTYPE html>
1045 <html>
1046 <head><title>Echo</title></head>
1047 <body>
1048 <script>
1049 const ws = new WebSocket('<%= url_for('echo')->to_abs %>');
1050 // Incoming messages
1052 ws.onmessage = function (event) {
1053 document.body.innerHTML += event.data + '<br/>';
1054 };
1055 // Outgoing messages
1057 ws.onopen = function (event) {
1058 window.setInterval(function () { ws.send('Hello Mojo!') }, 1000);
1059 };
1060 </script>
1061 </body>
1062 </html>
1063 The event "finish" in Mojo::Transaction::WebSocket will be emitted
1065 right after the WebSocket connection has been closed.
1066 $c->tx->with_compression;
1068 You can activate "permessage-deflate" compression with
1070 "with_compression" in Mojo::Transaction::WebSocket, this can result in
1071 much better performance, but also increases memory usage by up to
1072 300KiB per connection.
1073 my $proto = $c->tx->with_protocols('v2.proto', 'v1.proto');
1075 You can also use "with_protocols" in Mojo::Transaction::WebSocket to
1077 negotiate a subprotocol.
1078 EventSource web service
1080 EventSource is a special form of long polling where you can use "write"
1081 in Mojolicious::Controller to directly send DOM events from servers to
1082 clients. It is uni-directional, that means you will have to use Ajax
1083 requests for sending data from clients to servers, the advantage
1084 however is low infrastructure requirements, since it reuses the HTTP
1085 protocol for transport.
1086 use Mojolicious::Lite -signatures;
1088 # Template with browser-side code
1090 get '/' => 'index';
1091 # EventSource for log messages
1093 get '/events' => sub ($c) {
1094 # Increase inactivity timeout for connection a bit
1096 $c->inactivity_timeout(300);
1097 # Change content type and finalize response headers
1099 $c->res->headers->content_type('text/event-stream');
1100 $c->write;
1101 # Subscribe to "message" event and forward "log" events to browser
1103 my $cb = $c->app->log->on(message => sub ($log, $level, @lines) {
1104 $c->write("event:log\ndata: [$level] @lines\n\n");
1105 });
1106 # Unsubscribe from "message" event again once we are done
1108 $c->on(finish => sub ($c) {
1109 $c->app->log->unsubscribe(message => $cb);
1110 });
1111 };
1112 app->start;
1114 __DATA__
1115 @@ index.html.ep
1117 <!DOCTYPE html>
1118 <html>
1119 <head><title>LiveLog</title></head>
1120 <body>
1121 <script>
1122 const events = new EventSource('<%= url_for 'events' %>');
1123 // Subscribe to "log" event
1125 events.addEventListener('log', function (event) {
1126 document.body.innerHTML += event.data + '<br/>';
1127 }, false);
1128 </script>
1129 </body>
1130 </html>
1131 The event "message" in Mojo::Log will be emitted for every new log
1133 message and the event "finish" in Mojo::Transaction right after the
1134 transaction has been finished.
1135 Streaming multipart uploads
1137 Mojolicious contains a very sophisticated event system based on
1138 Mojo::EventEmitter, with ready-to-use events on almost all layers, and
1139 which can be combined to solve some of the hardest problems in web
1140 development.
1141 use Mojolicious::Lite -signatures;
1143 use Scalar::Util qw(weaken);
1144 # Intercept multipart uploads and log each chunk received
1146 hook after_build_tx => sub ($tx, $app) {
1147 # Subscribe to "upgrade" event to identify multipart uploads
1149 weaken $tx;
1150 $tx->req->content->on(upgrade => sub ($single, $multi) {
1151 return unless $tx->req->url->path->contains('/upload');
1152 # Subscribe to "part" event to find the right one
1154 $multi->on(part => sub ($multi, $single) {
1155 # Subscribe to "body" event of part to make sure we have all headers
1157 $single->on(body => sub ($single) {
1158 # Make sure we have the right part and replace "read" event
1160 return unless $single->headers->content_disposition =~ /example/;
1161 $single->unsubscribe('read')->on(read => sub ($single, $bytes) {
1162 # Log size of every chunk we receive
1164 $app->log->debug(length($bytes) . ' bytes uploaded');
1165 });
1166 });
1167 });
1168 });
1169 };
1170 # Upload form in DATA section
1172 get '/' => 'index';
1173 # Streaming multipart upload
1175 post '/upload' => {text => 'Upload was successful.'};
1176 app->start;
1178 __DATA__
1179 @@ index.html.ep
1181 <!DOCTYPE html>
1182 <html>
1183 <head><title>Streaming multipart upload</title></head>
1184 <body>
1185 %= form_for upload => (enctype => 'multipart/form-data') => begin
1186 %= file_field 'example'
1187 %= submit_button 'Upload'
1188 % end
1189 </body>
1190 </html>
1191 More event loops
1193 Internally, the Mojo::IOLoop event loop can use multiple reactor
1194 backends, EV for example, will be automatically used if possible. Which
1195 in turn allows other event loops like AnyEvent to just work.
1196 use Mojolicious::Lite -signatures;
1198 use EV;
1199 use AnyEvent;
1200 # Wait 3 seconds before rendering a response
1202 get '/' => sub ($c) {
1203 my $w;
1204 $w = AE::timer 3, 0, sub {
1205 $c->render(text => 'Delayed by 3 seconds!');
1206 undef $w;
1207 };
1208 };
1209 app->start;
1211
1213 When we say Mojolicious is a web framework we actually mean it, with
1214 Mojo::UserAgent there's a full featured HTTP and WebSocket user agent
1215 built right in.
1216 REST web services
1218 Requests can be performed very comfortably with methods like "get" in
1219 Mojo::UserAgent, and always result in a Mojo::Transaction::HTTP object,
1220 which has many useful attributes and methods. You can check for
1221 connection errors with "result" in Mojo::Transaction, or access HTTP
1222 request and response information directly through "req" in
1223 Mojo::Transaction and "res" in Mojo::Transaction.
1224 use Mojo::UserAgent;
1226 # Request a resource and make sure there were no connection errors
1228 my $ua = Mojo::UserAgent->new;
1229 my $tx = $ua->get('https://docs.mojolicious.org/Mojo' => {Accept => 'text/plain'});
1230 my $res = $tx->result;
1231 # Decide what to do with its representation
1233 if ($res->is_success) { say $res->body }
1234 elsif ($res->is_error) { say $res->message }
1235 elsif ($res->code == 301) { say $res->headers->location }
1236 else { say 'Whatever...' }
1237 While methods like "is_success" in Mojo::Message::Response and
1239 "is_error" in Mojo::Message::Response serve as building blocks for more
1240 sophisticated REST clients.
1241 Web scraping
1243 Scraping information from websites has never been this much fun before.
1244 The built-in HTML/XML parser Mojo::DOM is accessible through "dom" in
1245 Mojo::Message and supports all CSS selectors that make sense for a
1246 standalone parser, it can be a very powerful tool especially for
1247 testing web application.
1248 use Mojo::UserAgent;
1250 # Fetch website
1252 my $ua = Mojo::UserAgent->new;
1253 my $res = $ua->get('https://docs.mojolicious.org')->result;
1254 # Extract title
1256 say 'Title: ', $res->dom->at('head > title')->text;
1257 # Extract headings
1259 $res->dom('h1, h2, h3')->each(sub ($dom, $i) {
1260 say 'Heading: ', $dom->all_text;
1261 });
1262 # Visit all nodes recursively to extract more than just text
1264 for my $n ($res->dom->descendant_nodes->each) {
1265 # Text or CDATA node
1267 print $n->content if $n->type eq 'text' || $n->type eq 'cdata';
1268 # Also include alternate text for images
1270 print $n->{alt} if $n->type eq 'tag' && $n->tag eq 'img';
1271 }
1272 For a full list of available CSS selectors see "SELECTORS" in
1274 Mojo::DOM::CSS.
1275 JSON web services
1277 Most web services these days are based on the JSON data-interchange
1278 format. That's why Mojolicious comes with the possibly fastest pure-
1279 Perl implementation Mojo::JSON built right in, which is accessible
1280 through "json" in Mojo::Message.
1281 use Mojo::UserAgent;
1283 use Mojo::URL;
1284 # Fresh user agent
1286 my $ua = Mojo::UserAgent->new;
1287 # Search MetaCPAN for "mojolicious" and list latest releases
1289 my $url = Mojo::URL->new('http://fastapi.metacpan.org/v1/release/_search');
1290 $url->query({q => 'mojolicious', sort => 'date:desc'});
1291 for my $hit (@{$ua->get($url)->result->json->{hits}{hits}}) {
1292 say "$hit->{_source}{name} ($hit->{_source}{author})";
1293 }
1294 Basic authentication
1296 You can just add username and password to the URL, an "Authorization"
1297 header will be automatically generated.
1298 use Mojo::UserAgent;
1300 my $ua = Mojo::UserAgent->new;
1302 say $ua->get('https://sri:secret@example.com/hideout')->result->body;
1303 If you're using Mojo::URL to build the URL, be aware that the userinfo
1305 part will not be included if the object is stringified. You'll have to
1306 pass the object itself to Mojo::UserAgent or use "to_unsafe_string" in
1307 Mojo::URL.
1308 use Mojo::UserAgent;
1310 use Mojo::URL;
1311 my $ua = Mojo::UserAgent->new;
1313 my $url = Mojo::URL->new('https://example.com/hideout')->userinfo('sri:secret');
1314 say $ua->get($url)->result->body;
1315 Decorating follow-up requests
1317 Mojo::UserAgent can automatically follow redirects, the event "start"
1318 in Mojo::UserAgent allows you direct access to each transaction right
1319 after they have been initialized and before a connection gets
1320 associated with them.
1321 use Mojo::UserAgent;
1323 # User agent following up to 10 redirects
1325 my $ua = Mojo::UserAgent->new(max_redirects => 10);
1326 # Add a witty header to every request
1328 $ua->on(start => sub ($ua, $tx) {
1329 $tx->req->headers->header('X-Bender' => 'Bite my shiny metal ass!');
1330 say 'Request: ', $tx->req->url->clone->to_abs;
1331 });
1332 # Request that will most likely get redirected
1334 say 'Title: ', $ua->get('google.com')->result->dom->at('head > title')->text;
1335 This even works for proxy "CONNECT" requests.
1337 Content generators
1339 Content generators can be registered with "add_generator" in
1340 Mojo::UserAgent::Transactor to generate the same type of content
1341 repeatedly for multiple requests.
1342 use Mojo::UserAgent;
1344 use Mojo::Asset::File;
1345 # Add "stream" generator
1347 my $ua = Mojo::UserAgent->new;
1348 $ua->transactor->add_generator(stream => sub ($transactor, $tx, $path) {
1349 $tx->req->content->asset(Mojo::Asset::File->new(path => $path));
1350 });
1351 # Send multiple files streaming via PUT and POST
1353 $ua->put('http://example.com/upload' => stream => '/home/sri/mojo.png');
1354 $ua->post('http://example.com/upload' => stream => '/home/sri/minion.png');
1355 The "json", "form" and "multipart" content generators are always
1357 available.
1358 use Mojo::UserAgent;
1360 # Send "application/json" content via PATCH
1362 my $ua = Mojo::UserAgent->new;
1363 my $tx = $ua->patch('http://api.example.com' => json => {foo => 'bar'});
1364 # Send query parameters via GET
1366 my $tx2 = $ua->get('search.example.com' => form => {q => 'test'});
1367 # Send "application/x-www-form-urlencoded" content via POST
1369 my $tx3 = $ua->post('http://search.example.com' => form => {q => 'test'});
1370 # Send "multipart/form-data" content via PUT
1372 my $tx4 = $ua->put('upload.example.com' => form => {test => {content => 'Hello World!'}});
1373 # Send custom multipart content via PUT
1375 my $tx5 = $ua->put('api.example.com' => multipart => ['Hello', 'World!']);
1376 For more information about available content generators see also "tx"
1378 in Mojo::UserAgent::Transactor.
1379 Large file downloads
1381 When downloading large files with Mojo::UserAgent you don't have to
1382 worry about memory usage at all, because it will automatically stream
1383 everything above 250KiB into a temporary file, which can then be moved
1384 into a permanent file with "save_to" in Mojo::Message.
1385 use Mojo::UserAgent;
1387 # Fetch the latest Mojolicious tarball
1389 my $ua = Mojo::UserAgent->new(max_redirects => 5);
1390 my $tx = $ua->get('https://www.github.com/mojolicious/mojo/tarball/main');
1391 $tx->result->save_to('mojo.tar.gz');
1392 To protect you from excessively large files there is also a limit of
1394 2GiB by default, which you can tweak with the attribute
1395 "max_response_size" in Mojo::UserAgent.
1396 # Increase limit to 10GiB
1398 $ua->max_response_size(10737418240);
1399 Large file upload
1401 Uploading a large file is even easier.
1402 use Mojo::UserAgent;
1404 # Upload file via POST and "multipart/form-data"
1406 my $ua = Mojo::UserAgent->new;
1407 $ua->post('example.com/upload' => form => {image => {file => '/home/sri/hello.png'}});
1408 And once again you don't have to worry about memory usage, all data
1410 will be streamed directly from the file.
1411 Streaming response
1413 Receiving a streaming response can be really tricky in most HTTP
1414 clients, but Mojo::UserAgent makes it actually easy.
1415 use Mojo::UserAgent;
1417 # Accept responses of indefinite size
1419 my $ua = Mojo::UserAgent->new(max_response_size => 0);
1420 # Build a normal transaction
1422 my $tx = $ua->build_tx(GET => 'http://example.com');
1423 # Replace "read" events to disable default content parser
1425 $tx->res->content->unsubscribe('read')->on(read => sub ($content, $bytes) {
1426 say "Streaming: $bytes";
1427 });
1428 # Process transaction
1430 $tx = $ua->start($tx);
1431 The event "read" in Mojo::Content will be emitted for every chunk of
1433 data that is received, even chunked transfer encoding and gzip content
1434 encoding will be handled transparently if necessary.
1435 Streaming request
1437 Sending a streaming request is almost just as easy.
1438 use Mojo::UserAgent;
1440 # Build a normal transaction
1442 my $ua = Mojo::UserAgent->new;
1443 my $tx = $ua->build_tx(GET => 'http://example.com');
1444 # Prepare body
1446 my $body = 'Hello World!';
1447 $tx->req->headers->content_length(length $body);
1448 # Start writing directly with a drain callback
1450 my $drain = sub ($content) {
1451 my $chunk = substr $body, 0, 1, '';
1452 $content->write($chunk, length $body ? __SUB__ : undef);
1453 };
1454 $tx->req->content->$drain;
1455 # Process transaction
1457 $tx = $ua->start($tx);
1458 The drain callback passed to "write" in Mojo::Content will be executed
1460 whenever the entire previous chunk of data has actually been written.
1461 Non-blocking
1463 Mojo::UserAgent has been designed from the ground up to be non-
1464 blocking, the whole blocking API is just a simple convenience wrapper.
1465 Especially for high latency tasks like web crawling this can be
1466 extremely useful, because you can keep many concurrent connections
1467 active at the same time.
1468 use Mojo::UserAgent;
1470 use Mojo::IOLoop;
1471 # Concurrent non-blocking requests
1473 my $ua = Mojo::UserAgent->new;
1474 $ua->get('https://metacpan.org/search?q=mojo' => sub ($ua, $mojo) {
1475 say $mojo->result->dom->at('title')->text;
1476 });
1477 $ua->get('https://metacpan.org/search?q=minion' => sub ($ua, $minion) {
1478 say $minion->result->dom->at('title')->text;
1479 });
1480 # Start event loop if necessary
1482 Mojo::IOLoop->start unless Mojo::IOLoop->is_running;
1483 But don't try to open too many connections to one server at the same
1485 time, it might get overwhelmed. Better use a queue to process requests
1486 in smaller batches.
1487 use Mojo::Promise;
1489 use Mojo::UserAgent;
1490 my @urls = (
1492 'https://docs.mojolicious.org/Mojo/DOM', 'https://docs.mojolicious.org/Mojo',
1493 'https://docs.mojolicious.org/Mojo/File', 'https://docs.mojolicious.org/Mojo/URL'
1494 );
1495 # User agent with a custom name, following up to 5 redirects
1497 my $ua = Mojo::UserAgent->new(max_redirects => 5);
1498 $ua->transactor->name('MyParallelCrawler 1.0');
1499 # Use a promise to keep the event loop running until we are done
1501 my $promise = Mojo::Promise->new;
1502 my $count = 0;
1503 my $fetch = sub {
1504 # Stop if there are no more URLs
1506 return unless my $url = shift @urls;
1507 # Fetch the next title
1509 $ua->get($url => sub ($ua, $tx) {
1510 say "$url: ", $tx->result->dom->at('title')->text;
1511 # Next request
1513 __SUB__->();
1514 $promise->resolve if --$count == 0;
1515 });
1516 $count++;
1517 };
1518 # Process two requests at a time
1520 $fetch->() for 1 .. 2;
1521 $promise->wait;
1522 It is also strongly recommended to respect every sites "robots.txt"
1524 file as well as terms of service, and to wait a little before reopening
1525 connections to the same host, or the operators might be forced to block
1526 your access.
1527 Concurrent blocking requests
1529 You might have seen "wait" in Mojo::Promise already in some examples
1530 above. It is used to make non-blocking operations portable, allowing
1531 them to work inside an already running event loop or start one on
1532 demand.
1533 use Mojo::UserAgent;
1535 use Mojo::Promise;
1536 # Synchronize non-blocking requests with promises
1538 my $ua = Mojo::UserAgent->new;
1539 my $mojo_promise = $ua->get_p('https://metacpan.org/search?q=mojo');
1540 my $minion_promise = $ua->get_p('https://metacpan.org/search?q=minion');
1541 Mojo::Promise->all($mojo_promise, $minion_promise)->then(sub ($mojo, $minion) {
1542 say $mojo->[0]->result->dom->at('title')->text;
1543 say $minion->[0]->result->dom->at('title')->text;
1544 })->wait;
1545 WebSockets
1547 WebSockets are not just for the server-side, you can use "websocket_p"
1548 in Mojo::UserAgent to open new connections, which are always non-
1549 blocking. The WebSocket handshake uses HTTP, and is a normal "GET"
1550 request with a few additional headers. It can even contain cookies, and
1551 is followed by a 101 response from the server, notifying our user agent
1552 that the connection has been established and it can start using the bi-
1553 directional WebSocket protocol.
1554 use Mojo::UserAgent;
1556 use Mojo::Promise;
1557 # Open WebSocket to echo service
1559 my $ua = Mojo::UserAgent->new;
1560 $ua->websocket_p('ws://echo.websocket.org')->then(sub ($tx) {
1561 # Prepare a followup promise so we can wait for messages
1563 my $promise = Mojo::Promise->new;
1564 # Wait for WebSocket to be closed
1566 $tx->on(finish => sub ($tx, $code, $reason) {
1567 say "WebSocket closed with status $code.";
1568 $promise->resolve;
1569 });
1570 # Close WebSocket after receiving one message
1572 $tx->on(message => sub ($tx, $msg) {
1573 say "WebSocket message: $msg";
1574 $tx->finish;
1575 });
1576 # Send a message to the server
1578 $tx->send('Hi!');
1579 # Insert a new promise into the promise chain
1581 return $promise;
1582 })->catch(sub ($err) {
1583 # Handle failed WebSocket handshakes and other exceptions
1585 warn "WebSocket error: $err";
1586 })->wait;
1587 UNIX domain sockets
1589 Not just TCP/IP sockets are supported, but also UNIX domain sockets,
1590 which can have significant security and performance benefits when used
1591 for inter-process communication. Instead of "http://" and "ws://" you
1592 can use the "http+unix://" and "ws+unix://" schemes, and pass along a
1593 percent encoded path ("/" becomes %2F) instead of a hostname.
1594 use Mojo::UserAgent;
1596 use Mojo::Promise;
1597 # GET request via UNIX domain socket "/tmp/foo.sock"
1599 my $ua = Mojo::UserAgent->new;
1600 say $ua->get('http+unix://%2Ftmp%2Ffoo.sock/index.html')->result->body;
1601 # GET request with HOST header via UNIX domain socket "/tmp/bar.sock"
1603 my $tx = $ua->get('http+unix://%2Ftmp%2Fbar.sock' => {Host => 'example.com'});
1604 say $tx->result->body;
1605 # WebSocket connection via UNIX domain socket "/tmp/baz.sock"
1607 $ua->websocket_p('ws+unix://%2Ftmp%2Fbaz.sock/echo')->then(sub ($tx) {
1608 my $promise = Mojo::Promise->new;
1610 $tx->on(finish => sub ($tx) { $promise->resolve });
1611 $tx->on(message => sub ($tx, $msg) {
1613 say "WebSocket message: $msg";
1614 $tx->finish;
1615 });
1616 $tx->send('Hi!');
1617 return $promise;
1619 })->catch(sub ($err) {
1620 warn "WebSocket error: $err";
1621 })->wait;
1622 You can set the "Host" header manually to pass along a hostname.
1624 Command line
1626 Don't you hate checking huge HTML files from the command line? Thanks
1627 to the command Mojolicious::Command::get that is about to change. You
1628 can just pick the parts that actually matter with the CSS selectors
1629 from Mojo::DOM and JSON Pointers from Mojo::JSON::Pointer.
1630 $ mojo get https://mojolicious.org 'head > title'
1632 How about a list of all id attributes?
1634 $ mojo get https://mojolicious.org '*' attr id
1636 Or the text content of all heading tags?
1638 $ mojo get https://mojolicious.org 'h1, h2, h3' text
1640 Maybe just the text of the third heading?
1642 $ mojo get https://mojolicious.org 'h1, h2, h3' 3 text
1644 You can also extract all text from nested child elements.
1646 $ mojo get https://mojolicious.org '#mojobar' all
1648 The request can be customized as well.
1650 $ mojo get -M POST -H 'X-Bender: Bite my shiny metal ass!' http://google.com
1652 Store response data by redirecting "STDOUT".
1654 $ mojo get mojolicious.org > example.html
1656 Pass request data by redirecting "STDIN".
1658 $ mojo get -M PUT mojolicious.org < example.html
1660 Or use the output of another program.
1662 $ echo 'Hello World' | mojo get -M PUT https://mojolicious.org
1664 Submit forms as "application/x-www-form-urlencoded" content.
1666 $ mojo get -M POST -f 'q=Mojo' -f 'size=5' https://metacpan.org/search
1668 And upload files as "multipart/form-data" content.
1670 $ mojo get -M POST -f 'upload=@example.html' mojolicious.org
1672 You can follow redirects and view the headers for all messages.
1674 $ mojo get -r -v http://google.com 'head > title'
1676 Extract just the information you really need from JSON data structures.
1678 $ mojo get https://fastapi.metacpan.org/v1/author/SRI /name
1680 This can be an invaluable tool for testing your applications.
1682 $ ./myapp.pl get /welcome 'head > title'
1684 One-liners
1686 For quick hacks and especially testing, ojo one-liners are also a great
1687 choice.
1688 $ perl -Mojo -E 'say g("mojolicious.org")->dom->at("title")->text'
1690
1692 Fun Mojolicious application hacks for all occasions.
1693 Basic authentication
1695 Basic authentication data will be automatically extracted from the
1696 "Authorization" header.
1697 use Mojolicious::Lite -signatures;
1699 use Mojo::Util qw(secure_compare);
1700 get '/' => sub ($c) {
1702 # Check for username "Bender" and password "rocks"
1704 return $c->render(text => 'Hello Bender!') if secure_compare $c->req->url->to_abs->userinfo, 'Bender:rocks';
1705 # Require authentication
1707 $c->res->headers->www_authenticate('Basic');
1708 $c->render(text => 'Authentication required!', status => 401);
1709 };
1710 app->start;
1712 This can be combined with TLS for a secure authentication mechanism.
1714 $ ./myapp.pl daemon -l 'https://*:3000?cert=./server.crt&key=./server.key'
1716 Adding a configuration file
1718 Adding a configuration file to your application is as easy as adding a
1719 file to its home directory and loading the plugin
1720 Mojolicious::Plugin::Config. The default name is based on the value of
1721 "moniker" in Mojolicious ("myapp"), appended with a ".conf" extension
1722 ("myapp.conf").
1723 $ mkdir myapp
1725 $ cd myapp
1726 $ touch myapp.pl
1727 $ chmod 744 myapp.pl
1728 $ echo '{name => "my Mojolicious application"};' > myapp.conf
1729 Configuration files themselves are just Perl scripts that return a hash
1731 reference with configuration settings of your choice. All those
1732 settings are then available through the method "config" in Mojolicious
1733 and the helper "config" in Mojolicious::Plugin::DefaultHelpers.
1734 use Mojolicious::Lite;
1736 plugin 'Config';
1738 my $name = app->config('name');
1740 app->log->debug("Welcome to $name");
1741 get '/' => 'with_config';
1743 app->start;
1745 __DATA__
1746 @@ with_config.html.ep
1747 <!DOCTYPE html>
1748 <html>
1749 <head><title><%= config 'name' %></title></head>
1750 <body>Welcome to <%= config 'name' %></body>
1751 </html>
1752 Alternatively you can also use configuration files in the JSON format
1754 with Mojolicious::Plugin::JSONConfig.
1755 Adding a plugin to your application
1757 To organize your code better and to prevent helpers from cluttering
1758 your application, you can use application specific plugins.
1759 $ mkdir -p lib/MyApp/Plugin
1761 $ touch lib/MyApp/Plugin/MyHelpers.pm
1762 They work just like normal plugins and are also subclasses of
1764 Mojolicious::Plugin. Nested helpers with a prefix based on the plugin
1765 name are an easy way to avoid conflicts.
1766 package MyApp::Plugin::MyHelpers;
1768 use Mojo::Base 'Mojolicious::Plugin', -signatures;
1769 sub register ($self, $app, $conf) {
1771 $app->helper('my_helpers.render_with_header' => sub ($c, @args) {
1772 $c->res->headers->header('X-Mojo' => 'I <3 Mojolicious!');
1773 $c->render(@args);
1774 });
1775 }
1776 1;
1778 You can have as many application specific plugins as you like, the only
1780 difference to normal plugins is that you load them using their full
1781 class name.
1782 use Mojolicious::Lite -signatures;
1784 use lib qw(lib);
1786 plugin 'MyApp::Plugin::MyHelpers';
1788 get '/' => sub ($c) {
1790 $c->my_helpers->render_with_header(text => 'I ♥ Mojolicious!');
1791 };
1792 app->start;
1794 Of course these plugins can contain more than just helpers, take a look
1796 at "PLUGINS" in Mojolicious::Plugins for a few ideas.
1797 Adding commands to Mojolicious
1799 By now you've probably used many of the built-in commands described in
1800 Mojolicious::Commands, but did you know that you can just add new ones
1801 and that they will be picked up automatically by the command line
1802 interface if they are placed in a directory from @INC?
1803 package Mojolicious::Command::spy;
1805 use Mojo::Base 'Mojolicious::Command', -signatures;
1806 has description => 'Spy on application';
1808 has usage => "Usage: APPLICATION spy [TARGET]\n";
1809 sub run ($self, @args) {
1811 # Leak secret passphrases
1813 if ($args[0] eq 'secrets') { say for @{$self->app->secrets} }
1814 # Leak mode
1816 elsif ($args[0] eq 'mode') { say $self->app->mode }
1817 }
1818 1;
1820 Command line arguments are passed right through and there are many
1822 useful attributes and methods in Mojolicious::Command that you can use
1823 or overload.
1824 $ mojo spy secrets
1826 HelloWorld
1827 $ ./script/myapp spy secrets
1829 secr3t
1830 And to make your commands application specific, just add a custom
1832 namespace to "namespaces" in Mojolicious::Commands and use a class name
1833 like "MyApp::Command::spy" instead of "Mojolicious::Command::spy".
1834 # Application
1836 package MyApp;
1837 use Mojo::Base 'Mojolicious', -signatures;
1838 sub startup ($self) {
1840 # Add another namespace to load commands from
1842 push @{$self->commands->namespaces}, 'MyApp::Command';
1843 }
1844 1;
1846 The options "-h"/"--help", "--home" and "-m"/"--mode" are handled
1848 automatically by Mojolicious::Commands and are shared by all commands.
1849 $ ./script/myapp spy -m production mode
1851 production
1852 For a full list of shared options see "SYNOPSIS" in
1854 Mojolicious::Commands.
1855 Running code against your application
1857 Ever thought about running a quick one-liner against your Mojolicious
1858 application to test something? Thanks to the command
1859 Mojolicious::Command::eval you can do just that, the application object
1860 itself can be accessed via "app".
1861 $ mojo generate lite-app myapp.pl
1863 $ ./myapp.pl eval 'say for @{app->static->paths}'
1864 $ ./myapp.pl eval 'say for sort keys %{app->renderer->helpers}'
1865 The "verbose" options will automatically print the return value or
1867 returned data structure to "STDOUT".
1868 $ ./myapp.pl eval -v 'app->static->paths->[0]'
1870 $ ./myapp.pl eval -V 'app->static->paths'
1871 Making your application installable
1873 Ever thought about releasing your Mojolicious application to CPAN? It's
1874 actually much easier than you might think.
1875 $ mojo generate app MyApp
1877 $ cd my_app
1878 $ mv public lib/MyApp/
1879 $ mv templates lib/MyApp/
1880 The trick is to move the "public" and "templates" directories so they
1882 can get automatically installed with the modules. Additionally author
1883 commands from the "Mojolicious::Command::Author" namespace are not
1884 usually wanted by an installed application so they can be excluded.
1885 # Application
1887 package MyApp;
1888 use Mojo::Base 'Mojolicious', -signatures;
1889 use Mojo::File qw(curfile);
1891 use Mojo::Home;
1892 # Every CPAN module needs a version
1894 our $VERSION = '1.0';
1895 sub startup ($self) {
1897 # Switch to installable home directory
1899 $self->home(Mojo::Home->new(curfile->sibling('MyApp')));
1900 # Switch to installable "public" directory
1902 $self->static->paths->[0] = $self->home->child('public');
1903 # Switch to installable "templates" directory
1905 $self->renderer->paths->[0] = $self->home->child('templates');
1906 # Exclude author commands
1908 $self->commands->namespaces(['Mojolicious::Commands']);
1909 my $r = $self->routes;
1911 $r->get('/welcome')->to('example#welcome');
1912 }
1913 1;
1915 Finally there is just one small change to be made to the application
1917 script. The shebang line becomes the recommended "#!perl", which the
1918 toolchain can rewrite to the proper shebang during installation.
1919 #!perl
1921 use strict;
1923 use warnings;
1924 use Mojo::File qw(curfile);
1926 use lib curfile->dirname->sibling('lib')->to_string;
1927 use Mojolicious::Commands;
1928 # Start command line interface for application
1930 Mojolicious::Commands->start_app('MyApp');
1931 That's really everything, now you can package your application like any
1933 other CPAN module.
1934 $ ./script/my_app generate makefile
1936 $ perl Makefile.PL
1937 $ make test
1938 $ make manifest
1939 $ make dist
1940 And if you have a PAUSE account (which can be requested at
1942 <http://pause.perl.org>) even upload it.
1943 $ mojo cpanify -u USER -p PASS MyApp-0.01.tar.gz
1945 Proxy
1947 While every Mojolicious application has the built-in user agent "ua" in
1948 Mojolicious::Plugin::DefaultHelpers for you to perform requests to
1949 backend web services, this is not always the most efficient solution.
1950 The specialized proxy helpers "proxy->get_p" in
1951 Mojolicious::Plugin::DefaultHelpers and "proxy->start_p" in
1952 Mojolicious::Plugin::DefaultHelpers can stream response content
1953 straight to the client, as soon as a new chunk of data is received from
1954 the backend web service. Additionally they will take care of removing
1955 hop-by-hop headers and protect you automatically from backpressure
1956 issues. Which can happen in situations where the connection to the
1957 backend web service is faster than the connection to the client and
1958 data forwarding needs to be throttled. And the best of all, everything
1959 happens non-blocking, that means your web server can process other
1960 requestes concurrently while waiting for I/O.
1961 use Mojolicious::Lite -signatures;
1963 # Just forward the response
1965 get '/' => sub ($c) {
1966 $c->proxy->get_p('https://mojolicious.org')->catch(sub ($err) {
1967 $c->log->error("Proxy error: $err");
1968 $c->render(text => 'Could not connect to backend web service!', status => 400);
1969 });
1970 };
1971 # Forward response and customize a few things
1973 get '/*docs' => sub ($c) {
1974 # Custom request
1976 my $tx = $c->ua->build_tx(GET => 'https://docs.mojolicious.org');
1977 my $docs = $c->param('docs');
1978 $tx->req->url->path("/$docs");
1979 $tx->req->headers->user_agent('MojoProxy/1.0');
1980 # Start non-blocking request
1982 $c->proxy->start_p($tx)->catch(sub ($err) {
1983 $c->log->error("Proxy error: $err");
1984 $c->render(text => 'Could not connect to backend web service!', status => 400);
1985 });
1986 # Custom response
1988 $tx->res->content->once(body => sub ($content) {
1989 $c->res->headers->server('MojoProxy/1.0');
1990 });
1991 };
1992 app->start;
1994 All proxy helpers return a Mojo::Promise object, which should be used
1996 to handle connection errors to backend web services gracefully. And if
1997 you ever need to forward all headers from the client to the backend web
1998 service, make sure to use "dehop" in Mojo::Headers to remove all hop-
1999 by-hop headers.
2000 # Clone and modify request headers
2002 my $headers = $c->req->headers->clone->dehop;
2003 $headers->accept('application/json');
2004 my $tx = $c->ua->build_tx(PUT => 'https://mojolicious.org' => $headers->to_hash);
2005 Hello World
2007 If every byte matters this is the smallest "Hello World" application
2008 you can write with Mojolicious::Lite.
2009 use Mojolicious::Lite;
2011 any {text => 'Hello World!'};
2012 app->start;
2013 It works because all routes without a pattern default to "/" and
2015 automatic rendering kicks in even if no actual code gets executed by
2016 the router. The renderer just picks up the "text" value from the stash
2017 and generates a response.
2018 Hello World one-liners
2020 The "Hello World" example above can get even a little bit shorter in an
2021 ojo one-liner.
2022 $ perl -Mojo -E 'a({text => "Hello World!"})->start' daemon
2024 And you can use all the commands from Mojolicious::Commands.
2026 $ perl -Mojo -E 'a({text => "Hello World!"})->start' get -v /
2028
2030 You can continue with Mojolicious::Guides now or take a look at the
2031 Mojolicious wiki <https://github.com/mojolicious/mojo/wiki>, which
2032 contains a lot more documentation and examples by many different
2033 authors.
2034
2036 If you have any questions the documentation might not yet answer, don't
2037 hesitate to ask in the Forum <https://forum.mojolicious.org>, on Matrix
2038 <https://matrix.to/#/#mojo:matrix.org>, or IRC
2039 <https://web.libera.chat/#mojo>.
2040perl v5.36.0 2022-07-22 Mojolicious::Guides::Cookbook(3)