Friday, April 17, 2009

Some thoughts on Kanban in Software Development

I recently watched a presentation given by David Anderson at QCon 2008 on his experience and observations of a kanban system applied in a software engineering environment. I found some of the observations very interesting, particularly the approach that optimising the system for lowest cost didn't actually result in the most efficient system in terms of optimal throughput. As with many great ideas, kanban appears to be a very simple concept; however clearly there is more to it than just a simple approach at managing a flow of post-it notes on a whiteboard.

I was keen to understand more about kanban and how it might be applied in various project scenarios. At the SPA2009 conference, there was a session presented by Karl Scotland on his take on kanban (Kanban, Flow and Cadence) together with a very interactive BoF session on Lean and Kanban. Whilst the comparison of lean, based on a model, originally promoted by Toyota, of optimising production, against kanban, which limits the work in progress was a  simple and very understandable comparison of the two approaches, it was when the debate moved to seeing how both lean and kanban could be applied to software developments that the debate got really interesting. 

Clearly software developments come in all shapes and sizes and the audience clearly represented a good cross section of developments and associated practices. Both approaches are clearly well suited to an agile approach in which features are developed to provide a flow of (increasing) value to the end user. This works particularly well in an iterative development where frequent delivery is encouraged, especially where the features are being evolved based on user feedback. This also requires a tolerant customer who can accommodate some failures. An interesting statement of 'get it right second time' was  promoted as acceptable provided you learn from mistakes. I find that hard to accept as the 'norm' because it is completely ignoring any recognition of embedding quality in a delivered product. It might be acceptable in a prototype development but not in a production environment. Clearly there was something missing. There was! The integration step. Now I consider integration to be a very important (and potentially very expensive) stage, which is often squeezed in terms of time (how do you know you have finished?), and can't be omitted.

So could kanban work in a more traditional waterfall development approach? Maybe. In a traditional approach, the requirements are analysed before design, implementation and testing are performed. Using a kanban system, a flow of features could be pushed through the separate stages of design, implementation and testing before handing over to integration, with limits being imposed at each stage. This would probably require that the 3 life cycle stages are performed by different team members, a not unreasonable expectation in a traditional development. Provided the requirements are relatively stable and the ordering and independence of features is organised to support a sensible integration approach in order to deliver increasing value (or functionality) then this could be an interesting approach. Managing the queues at each stage of the life cycle needs to be carefully managed since the costs of managing each queue must be proportional to the size of the queue otherwise the process becomes very inefficient. 

Now for the challenge. How likely is it that each feature will be take approximately the same time through the life cycle? - probably not. In my experience, it is highly unlikely that each requirement (or feature) will be equivalent in terms of effort expended, particularly when the software forms part of a complex system. This will result in some initial  inefficiency as it would take some time for the queues to become populated with tasks. There is the temptation to process easy requirements first as a way of seeding the work queues quickly. However, from a project management perspective this is probably not what is required as it leaves the difficult tasks (and hence risks) to the end (and most difficult tasks will probably impinge on the easier tasks in some form resulting in some additional unplanned work).

Looking back at the David Anderson presentation, it is clear why a kanban approach worked well in one of the case studies since the approach was only applied to bug fixing rather than  in a new development. I believe that looking at kanban in a multiple life cycle development needs a different approach for development with the queues being placed at different points in the system life cycle (as distinct from the software life cycle) to avoid bottlenecks building up. I would advocate that the same developer should be responsible for design, implementation and testing of each feature so that the queue limits are placed on the exit from analysis (or requirements definition) and entry into integration rather than within the different stages of software development. In a lean or agile development this approach is normal since the developers are performing all stages of the life cycle; in waterfall developments, and particularly large systems, this is not the norm. 

Adopting kanban in waterfall certainly isn't new (see Kenji Hiranbe's article) but there is little evidence currently to demonstrate if it can deliver tangible benefits for all types of project approaches. Are there any case studies to prove or disprove my hypothesis?

Monday, April 13, 2009

Web Security - an eyeopener

An impromptu Birds of a Feather (BoF) session given by Dave Misell at the SPA Conference admirally demonstrated what happens behind your back when you visit a website. Key to the demonstration was showing (very simply) how much data is passed between sites using cookies and how much data is retained (for considerable length of time in some cases) between site visits.

The session used the Paros proxy server with Firefox which easily showed the web transactions when entering a simple URL (I won't disclose the URLs used in the demonstration, suffice to say that the sites were well-known). Using Paros, it is easy to see how much information is passed via cookies. Stopping cookies results in the same information being passed via URL (although this is more obvious since the data appears in some form in the address bar). In many cases the same data is passed to a number if websites regardless of whether the data is appropriate or useful to the receiving website.

Although it is possible to see the information being sent to a website, it is not possible to determine what is done with the data by the receiving site. In most cases the data is used to trace a journey through website (so that the 'user experience' can be improved) which is totally transparent to the user since these are performed server side.

So is it possible to stop the information being transferred? Not easily, but choose your sites carefully. There is some legislation in the EU which has tightened up the exchange of information through websites, particulalry to third parties, without the express permission of the user. Unfortunatley this legislation is dependent on where the website is hosted, which isn't always obvious from a simple URL. There is always 'education' which applies to both the end user and also to the developers of the site, and there are some good courses now which can help (e.g. ethical hacking and MSc in Information Security at Royal Holloway College in London) increase awareness.

Thursday, April 9, 2009

Can you scrum on your own?

An interesting question posed by Peter Bell at this year's SPA conference. His premise was that some of the lean and agile approaches can be equally applicable when you are THE team. He called his approach Solo Scrum.

Peter identified a couple of scenarios where he felt that 'Solo Scrum' could be appropriate:
  • A full time developer doing open source development part-time
  • A solo consultant developing applications for non-technical clients
  • A 'work at home' contractor managing multiple clients
Clearly working on your own brings a number of challenges (note that I didn't say problems!) which need to be considered when working on your own. I think that probably one of the biggest challenges to overcome, (and this is based on personal experience), is to try and avoid too many distractions within the 'home' work area. The second challenge is that of loneliness! In the many (professional) development projects that I have worked, talking to colleagues has been a great way of confirming your thoughts for a solution or helping to find a way through a problem. When you are on your own, this isn't possible, or is it? However the use of technology can certainly help (think of IM, email, VOIP (with video)) and it can certainly be seen as 'virtual' pair programming. This isn't a new idea (see here); however, there is still the problem of finding a suitable 'pair' to link up with.

The traditional problems of planning don't go away when working on your own (as I said at the session 'Fail to plan, plan to fail'). Working on your own necessitates an efficient process for planning and managing the plan (a bit more than the 'back of an envelope' note). There are a number of Eclipse plugins (e.g. mylyn) which offer the right balance in terms of monitoring the work activity without distracting from the task-at-hand.

Some interesting ideas were discussed, including the observation that many team collaboration software packages often includes a free version for a small team (where small can be up to 5). This can overcome a often heard comment which was that I don't have the time/experience/etc to set up a 'professional' development environment (the minimum being a source control system, an IDE and a bug tracking system) from scratch.

Peter has now started a Google group to further the debate. I will watch with interest.


Having attended last year's conference and thoroughly enjoyed it, I was disappointed that my work commitments meant that I could only attend a single day of this year's conference. Attending a single day meant that I was keen to catch as much of the buzz as possible as well as catching up with some friends. I managed to attend 2 sessions, on AJAX web testing using Selenium and Solo Scrum, together with 2 BoF sessions on Web security (or lack of it) and Lean/Kanban in a stimulating day. I will summarise my notes over the next few days.