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All about Mojolicious – interview of Sebastian Riedel part 1

2014 November 26
by Nikos Vaggalis






Our journey into the world of Perl’s Web frameworks would not be complete without Mojolicious, therefore we talked to Sebastian Riedel, Mojolicious’ mastermind and Catalyst’s original founder.

We looked at Mojolicious’ history: why Sebastian left Catalyst for Mojolicious, present: what does the framework actually do, the project’s future: Sebastian’s long-term plans, and whether Perl6 will have an effect on the project. We also get more technical with questions like why not opt for a DSL like Dancer does, what is meant by ‘real time web framework’, whether the framework is dependency free and much more.

NV: Do you think that now with Mojolicious, Catalyst and Dancer we are experiencing Perl’s newest and most successful Web revolution since the 90’s?

SR: It’s certainly a great time for web development with Perl, and it has been a lot of fun seeing Catalyst and Mojolicious take the Perl community by storm.

But for a real revolution, along the lines of in the late 90s, I think we have to get a lot better at reaching people outside the echo chamber, which is not really a technical, but a public relations problem.

NV: Why did you leave Catalyst for Mojolicious?

SR: Creative differences. At the time I was still experimenting a lot with new ideas for Catalyst, many of which are now part of Mojolicious, but what the majority of core team members really wanted was stability.

So rather than risk harming Catalyst with a drawn-out fight, I decided to leave for a fresh start.
It was very disappointing at the time, but the right decision in retrospect.

NV: Is Mojolicious a MVC framework and if so how does it implement the MVC pattern?

Yes, it is very similar to Catalyst in that regard. But we don’t highlight the fact very much, Model-View-Controller is just one of many design patterns we use.

Out of the box, Mojolicious is Model layer agnostic, and we consider web applications simply frontends to existing business logic. Controllers are plain old Perl classes, connecting this existing business logic to a View, which would usually be EP (Embedded Perl), or one of the many other template systems we support.

NV: There are many web frameworks out there each one targeting various areas of web development. Which ones does Mojolicious address and how does it compare to Dancer and Catalyst?

SR: There was a time when I would jump at every opportunity to learn more about all the different web frameworks out there, searching for inspiration.

But these days there’s actually very little innovation happening, almost all server-side frameworks follow the same basic formula.Some are trying to optimize for projects of a certain size, but it’s mostly just programming languages competing now.

So I only really pay attention to a very small number that is still experimenting with different architectures and technologies, usually written in languages other than Perl. Some recent examples would be Meteor (JavaScript) and Play Framework (Scala).

What’s really important to me with Mojolicious, and what I believe really differentiates it from everything else in Perl, is that we are always trying new things. Like we’ve done with tight integration of WebSockets and event loops, or the ability to grow from single-file prototypes to well structured web applications.

NV: What is the term ‘real time web framework’ referring to? To the capability of doing WebSockets, non-blocking I/O and event loops? Can you walk us through these concepts? Do such features make Mojolicious a prime platform for building Web APIs?

SR: The real-time web is simply a collection of technologies that allow content to be pushed to consumers with long-lived connections, as soon as it is generated. One of these technologies is the WebSocket protocol, offering full bi-directional low-latency communication channels between the browser and your web server.

I’m not actually a big fan of non-blocking I/O and event loops, but they are the tools that allow us to scale.So a single WebSocket server process can handle thousands of connections concurrently.

Sounds rather complicated, doesn’t it? But with Mojolicious all you need are these 9 lines of Perl code, and you have a fully functioning real-time web application :

   use Mojolicious::Lite;
    use 5.20.0;
    use experimental 'signatures';

    websocket '/echo' => sub ($c) {
      $c->on(message => sub ($c, $msg) {
        $c->send("echo: $msg");


You tell me if this makes Mojolicious a “prime platform for building Web APIs”. :)

NV: How easy is to extend the framework with plugins and what are some of the most useful one?

Mojolicious has 415 reverse dependencies on MetaCPAN, so i’d say it is pretty easy to extend. While there are many many good ones, I have a weak spot for Mojolicious::Plugin::AssetPack, which takes care of all those annoying little asset management tasks, like minifying JavaScript and CSS files.

Mojolicious::Plugin::I18N and Mojolicious::Plugin::Mail are also very commonly used, and I guess I should mention my own Mojolicious::Plugin::Minion, which is a job queue designed specifically for Mojolicious.

In the next and final part, Sebastian shares his views on DSL’s, the project’s dependability and the upcoming release of Perl 6 for production use among others.

Nikos Vaggalis has a BSc in Computer Science and a MSc in Interactive Multimedia. He works as a Database Developer with Linux and Ingres, and programs in both Perl and C#. As a journalist he writes articles, conducts interviews and reviews technical IT books

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