The Future of Catalyst, or the Fifty Year Framework


Wrap up of Advent 2014, musings on the future.

Ten Years of Catalyst

From the Changes file:

    2.99_12  2005-01-28 22:00:00 2005
            - first development release

Well, its been a fast ten years hasn't it? I've been lucky enough to have now several jobs where Catalyst played an important part of the technology stack and I've been grateful for the career opportunities and work life stability that has given me. As I am sure many of you also feel. And I am pleased that I've been able to spend so much time with this framework, which I consider a seminal Modern Perl project. From my outlook nearly everything is better now than ten years ago.

But I think this is not a great time to think about all the past things. For sure Catalyst still evolves and has managed to change itself over time to meet new developer needs. That is a task that is ongoing and probably is always behind schedule. And although we did a lot I can't help but feel slightly sad that we did not manage to achieve more notoriety beyond our circle, as compared to similar frameworks in other languages that date from around the same time. However the question I often find myself thinking lately is what can I do to make sure the next ten years of Catalyst are as at least successful as the first ten, if not more so. Which leads me to think about what in Catalyst is changing, and how we make decisions about change.

Catalyst change management process

In general there are two rules I use when thinking about changing Catalyst. The first is technical merit of the idea. If there is a bug, then its obvious it needs to be fixed. Less obvious is the types of refactoring that went into giving Catalyst modern features like websocket support, interoperability with event loops and to expose more and more of Catalyst's PSGI underpinnings.

When an idea has strong technical merit, it recommends itself. The only thing to consider is the needs of backward compatibility, and to offer people upgrading at least some sort of path forward when features change (such as to have plugins or configuration options to replace or replicate something that is no longer available).

Then there is a second and more difficult type of change consideration, which is the general will of the community. Like technical merit, this needs to balance against our commitment to not leave existing users high and dry with changes that break code and offer no path forward that does not involve significant code rewrites. Unlike technical merit, the will of the community can be hard to figure. In general we don't get a lot of bug reports or conversation around Catalyst future evolution. I wish I could find a way to get more involvement, but I also understand this is not very unusual issue for open source projects. I personally don't believe that "silence is consent" either. I think choices need to have broad acceptability or the choosers lose respect and authority. Typical that results in people just drifting away.

Without direct involvement the only other way to measure the will of the community is to look at what other choices people are making and what other projects have received the acceptance of a broad number of people. Since Plack is clearly accepted and important it leads me to feel the choice to make Catalyst expose more of its Plack nature and to better play with the larger Plack ecosystem are correct ones. One can also pay attention to the kinds of problems that get reported on IRC, at conferences and the problems that I see having looked at how Catalyst has been used in the wild. For example its clear that Chaining actions could use a tweak in some way since it seems to trip up people a lot. The same goes with $c->forward and $c->go, which tend to lead to confusing code (and combined with the stash is a particularly toxic brew).

Going further, if we allow ourselves to look hard at projects outside of Perl we can get lots of great ideas about what has worked for other projects in other languages. When we see certain features and approaches have excited programmers using frameworks like Ruby on Rails, Django, Scala Play, etc. then it should provide us with with help in thinking about how those features might influence the evolution of Catalyst as well.


Given all that, what could 2015 look like? I fully expect to see us stabilize all the great new UTF8 and encoding fixes and to start building some community practices to help people solve complex encoding problems. I also expect to see us continue to move more features into the middleware layer, such that over time most of what we think of as the Catalyst context would be mostly an interface over the Plack $env.

Thinking bigger, I've been asked when if ever will we have a version of Catalyst that does more to discard the technical debt of the past. I am very committed to offering people a path forward, even if Catalyst Six is built on a newer, cleaner codebase, you should be able to run your existing applications. I believe that we can do this because now that Catalyst exposes so much of its Plack roots it is possible to think that we could have a version of Catalyst Six which could mount over the PSGI interface a "Catalyst 5 VM" so to speak. So in a similar way that Apple migrated from OS9 to OSX, Catalyst 5 can migrate to a Catalyst Six. It would be work but it would be possible to think you could have Catalyst 5 and Six controllers and models side by side, and the application would automatically do all the needed piping. That way you could migration code as it needed and as you had time and will.

So that is the way we could do it, yet I think in 2015 we really need to answer the questions "What are we changing, and why, and how is it going to make it better?" Otherwise there's no point in taking the risk of alienating those who have spend many years learning and building applications on top of the Catalyst core we all know and use everyday.

Towards that end I initiated a documentation project a few months back with the intention of summarizing core Catalyst code and concepts. The idea is we we fully understand what we are today, we can more easily generate a diff to tomorrow. The project is currently an outline and you can see it (and send pull requests to)

My hope is that the community can help me at least ask the correct questions, so please take a look and send a PR or open an issue with your thoughts. I've also considered making a request for a grant from the Perl Foundation in order to work on these docs, and wonder what you all think of that :)

Until we can correctly answer all these questions, I will continue to push to change Catalyst in ways that technical merit themselves, and to do what I can do to make a transition as I've outlined above more possible.


Like all open source projects Catalyst needs community involvement at all levels in order to continue to evolve in a direction that maintains relevance for today and the future. As we begin the tenth year of Catalyst it will be that involvement which determines if our usefulness will fade or if we continue to meet our ever changing needs for a Modern Perl web framework.


John Napiorkowski