This isn’t quite as insane as it might appear. Remember that we have some rather specific non-functional requirements. We [the BBC] need to use Perl, there are restrictions on which libraries can and can’t be installed on the live environment and we needed a framework that could handle significant load. What we’ve built ticks all those boxes. Our benchmarking figures point to significantly better performance than Ruby on Rails (at least for the applications we are building), it can live in the BBC technical ecosystem and it provides a familiar API to our web development and software engineering teams with a nice clean separation of duties with rendering completely separated from models and controllers.
We’ve also adopted an open source approach to its development which is already starting to bear fruit and is personally and professionally hugely rewarding.
In general the BBC’s Software Engineering community is pretty good at sharing code. If one team has something that might be useful elsewhere then there’s no problem in installing it and using it elsewhere. What we’re not so good at is coordinating our effort so that we can all contribute to the same code base – in short we don’t really have an open source mentality between teams – we’re more cathedral and less bazaar even if we freely let each other into our cathedrals.
With the Perl on Rails framework I was keen to adopted a much more open source model – and actively encouraged other teams around the BBC to contribute code – and that’s pretty much what we’ve done. In the few weeks since the programmes beta launch JSON and YAML views have been written – due to go live next month. Integration with the BBC’s centrally managed controlled vocabulary – to provide accurate term extraction and therefore programme aggregation by subject, person or place – is well underway and should be with us in the new year. And finally the iPlayer team are building the next generation iPlayer browse using the framework. All this activity is great news. With multiple teams contributing code (rather than forking it) everyone benefits from faster development cycles, less bureaucracy and enhanced functionality.
We’re releasing the ‘Perl on Rails’ code under an open source license. James has just written about this and about the BBC’s infrastructure over at the BBC’s Internet blog in response to the I am Seb’s post.
Wow! Well this certainly generated quite a lot of interest. I’m not sure that I will be able to address everyone’s issues – especially all the folk over at slashdot but I’ll write another post to address as much as I can, in the meantime I just wanted to pick up on a few of the major themes.
Why didn’t we use Catalyst or something else that already existed? As Duncan indicated the simple answer is because we can’t install Catalyst etc. on the live environment. The BBC’s infrastructure is limited to Perl 5.6 with a limited set of approved modules and there are further limitation on what is allowed (making unmoderated system calls etc.)
Access to the code: I’ll see what I can do. The BBC does open source some of its code at http://www.bbc.co.uk/opensource/, I’m don’t know if we will be able to open source this code but I’ll let you know. However, its worth bearing in mind that we ended up writing this app to work within the BBC’s infrastructure (Perl 5.6, BBC approved modules etc.) so if we did release the code under an OSS license we would still need to maintain this requirement (clearly the code could be forked etc.)
Too many files on a file system: @Viad R. nice solution and yes that solves the seek time issue – unfortunately it doesn’t solve the other problems we needed solving. These include building the sort of interactive products we want to build; nor how to maintain up to date links between pages – when we publish information about a programme we not only need to publish a page for that programme but also update a large number of other pages that should now link to it/ or remove those that shouldn’t – trying to work out what pages to update becomes a nightmare, its much easier to render the pages dynamically.
BBC web infrastructure – not sure were to start with this one. You my find this hard to believe but the vast majority of bbc.co.uk is published statically – people write HTML and FTP those files onto the live servers. This provides a reliable service, if not a dreadfully exciting one. Its also clearly restrictive which is why we needed to build a solution like this in the first place, rather than using an existing framework. Now I’m very aware that this whole endeavor – building ‘Perl on Rails’ – seems bonkers to most people outside the BBC. But what isn’t bonkers is the fact that we have built an elegant application (with a small team) and deployed it within the constraints of the infrastructure and in doing so delivered a new product to our users and helped move the debate on inside the BBC.
Since I posted about this work there’s been quite a lot of chat about why we didn’t simply use an existing framework – like Catalyst for example. The simple answer is we can’t – we are restricted in what can be installed on the live environment (Perl 5.6 etc.) ‘I am Seb’ has some more information on the infrastructure. Believe me if we could have simply used an existing framework then we would have done – we all want to build great audience facing services – unfortunately to get there we sometimes need to do some unusual foundation work first. Still now that we’ve done it we can get on with building some great web apps.