Continuous Integration: The Last Mile
Conquering the Last Mile
I went to the London C.I. Meetup recently where Gus Power (how he chose a career in I.T. and not as a pro-wrestler with a name like that I do NOT know) delivered a talk entitled “C.I. The Last Mile”. Gus seems to have a comprehensive and varied background in lean and agile software engineering and delivery, and in this session he talked to us about “Conquering the last mile”, that is, getting working software out of the door.
We’ve all heard (or maybe even said a few times) the oft repeated mantra “but it works fine on my machine!”. This situation is commonplace, a build, for instance, will run just fine on your own PC, but as soon as it runs on the build server, it fails. Gus reminds us that, although this scenario is common, it’s a million miles away from working, releseable software, for a number of reasons, and that the only true definition of “working” software is “running, tested, and in the hands of the customer”.
Continuous Integration – is it Just a “Software” Practice?
Continuous Integration as a practice is traditionally quite a few steps removed from the world of running, tested software in the hands of the customer. In fact, Gus suggested that C.I. is usually associated with automating builds and running unit tests (although I would suggest that this is probably an increasingly naive view in this day and age, but for the sake of his talk it helped to make a point). This is obviously a long way away from delivering working software to a customer. Gus told us of his own company’s realisation that software, in their case, was not the product, and that their “product” included a lot more than just the software that the dev team delivered. He was of course referring to the supporting software and systems, and infrastructure.
Think of a web-based company, for instance Uswitch.com (for whom I used to work). While their core product may be a lot of web pages and associated content, their overall system consists of a lot more – for instance, there’s the IIS configurations, the data in the databases, the load balancers and of course the infrastructure (servers, Operating Systems etc). Note that Continuous Integration, in many cases, doesn’t cover most of this supporting system, only the company’s proprietary software (including the database in the case of Uswitch.com – at least, that was the case a few years ago when i worked there).
Gus pointed out that all these other parts of the system should also be brought under the watchful eye of Continuous Integration, and I agree with him wholeheartedly.
Gus went on to introduce us to the Lean Manufacturing model as used by Toyota.
He said that Toyota enjoy a great deal of success due to their use of a system based on tolerances, rather than rigid specs. He seemed to suggest that this approach could be applied to some of the non-software aspects of a system, such as infrastructure.
Acceptance Criteria for Systems
I think Gus raised a particularly interesting point about the lean manufacturing system, and it made me think about how much attention we usually pay to “acceptance criteria”. In the current agile environment, much attention is focused on what constitutes “acceptance” when it comes to designing and delivering software. Many tools exist, such as Fitnesse and Cucumber, which allow us to capture acceptance criteria in relation to a user story or use case. However, while this practice is now common across many software companies, the focus tends to be on the software that’s being developed, and often doesn’t include the supporting parts of the system, such as the infrastructure (hardware, load balancers, data, etc and so forth).
Of course, there’s an obvious reason for this. Most of the stories come from user requirements, the stories are made into tasks and the tasks are worked on by the software engineers. There’s a disconnect between those responsible for delivering the software (i.e. the software engineers) and those responsible for the supporting systems (who are they anyway???). Also, the customer’s requirements are often agnostic when it comes to the supporting parts of the system – they generally don’t care about the load balancer’s capabilities, or what type of web server you use).
What we’re talking about here is the difference between “software requirements” and “system requirements”, and how the latter are quite often overlooked, or at least overshadowed by the former.
Software Acceptance vs Product Acceptance
Gus finished off his talk by recommending that all parts of your “product” (I prefer the term “system” here, but that’s just me) should be brought under the control of your C.I. system and that there should be some effort to capture and measure system acceptance criteria – here he refers back to the Toyota system of using tolerances.
I raised the subject of Chef & Puppet in the Q&A session at the end. These tools allow you to treat what are traditionally considered “infrastructure” parts of your system as code. With these tools you can easily script up and deploy VMs and Operating Systems along with their configurations, and they also work well in a C.I. environment. Gus said that he has enjoyed some success with Chef.
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