Developing webapps with Mojolicious is a lot of fun! Using the morbo server for development, every change to my webapp causes a restart to load my changes. This way the next request I make has all my new code!

So, I change my code, the webapp restarts, and I go back to my browser window. Wait... Where's my new code? Why isn't the bug fixed? Did... Did I forget to reload my browser window again? Ugh! Of course!

Does this happen to you? Probably not. But, it's still annoying to reload the browser window after every backend code change. It'd be nice if my browser window automatically reloaded every time the web server restarted!

AutoReload Plugin

Like every problem in Perl, there's a CPAN module for this: Mojolicious::Plugin::AutoReload. Adding this plugin to our application will automatically reload any browser windows connected to our app, making it even easier to develop Mojolicious applications!

To use the plugin, we add it to our application using the plugin method. Then, we add the auto_reload helper to our layout template

use Mojolicious::Lite;

plugin 'AutoReload';
get '/' => 'index';


@@ layouts/default.html.ep
%= auto_reload
%= content

@@ index.html.ep
% layout 'default';
<h1>Hello, World!</h1>

Download the code here. Now while we have our application open in our browser, if the server is restarted, our browser will reload the page to see the new app!

How It Works

This plugin is sheer elegance in its simplicity: When the browser loads the page, it connects to a WebSocket located at /auto_reload. When the server restarts, the WebSocket connection is broken. The client sees the broken connection, waits a second for the server to start listening for connections again, and then reloads the page.

Disable In Production

Once we switch from morbo to hypnotoad, we don't want the automatic reload anymore. So, the plugin doesn't send the browser the JavaScript to build the websocket. This is controlled with the mode attribute. When the mode is development (the default for morbo), the browser is told to make the WebSocket. When the mode is anything else, no WebSocket is made.

Part of what makes Mojolicious so much fun is how easy it is. The entire plugin is only 40 lines of code.

And now, with Mojolicious::Plugin::AutoReload, developing in Mojolicious is just a little easier, and a little more fun!

Original artwork by Doug Bell, released under CC-BY-SA 4.0. It includes a screenshot of the website (fair use), the Mojolicious logo (CC-BY-SA 4.0), and a "reload" icon from Wikimedia Commons (CC0: Public domain)

Tagged in : advent, development

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Doug Bell

Doug (preaction) is a long time Perl user. He is the current maintainer of CPAN Testers and the author of many CPAN modules including the Statocles blog engine that powers this site.