On fragmented layers

In a previous post I described a layered approach to an organization. This time I'd like to extend the model a little and give some areas where it might be a useful decision-making tool. You can see a figure of the stack on the left. The point of the model is that different layers deal with different aspects of how an organization is built and that they are highly interdependent with changes in any of them causing a cascade of changes both upwards and down. It's also worth noting that, almost by definition, all projects impact all of the layers. Usually new pieces are added to the ends so somebody needs to make sure that the picture stays consistent, new pieces fit with existing stuff and do not cause discrepancies with others. All of this is pretty straightforward for the technical architecture but is often disregarded for the other aspects of a business.

How would one use the model in real life? One useful application I have found is explaining people why they should consider other things (like new processes or even teams) besides functionality when they are setting up a project. It also helps to visualize responsibilities (who deals with the functional architecture in your company?).

One use I'd like to focus a little more on, is the fragmentation aspect of the model. In short, the message goes: if you are to crack a layer, you better align it with cracks in neighboring ones.

Consider, for example, a scenario when you have two web applications supported by two different business organizations on two different continents. Which means there's a division in both business and organizational layers. Of course, the crack runs all the way and the applications are not integrated in any way. Now what if somebody up in the management decides, very sensibly, that it really sucks that customers would need to go to two different stores to get their SkypeOut minutes and headsets. Makes perfect sense and just making two systems talk to each other is not a fundamental obstacle. However, could you imagine two teams 4 timezones apart sharing responsibility for what the same piece of code does (i.e. integrating the technical architecture)? Or could you imagine an actual purchase flow (functional architecture) where you buy a SkypeIN number with all of it's details and finesse of all the legal requirements we have there and at the same time compare 4 headsets? Quite difficult, isn't it? Of course all of this could be done actually, but just linking the infrastructure without thinking of the organizational (how is responsibility shared among the teams?), functional (how do the different purchase flows fit together?), business (what about revenues and, say, marketing costs of the banners in the store?) or support (do our, say, release cycles need to be synchronized with the ones of our partner) dependencies are handled makes little sense.

Time to review

There has been yet another case of rebellion in wonderland recently. Basically, a design decision was challenged long after it had been made and also implemented. A year ago, we had designed (and implemented) a system that had a substantial influence to some billing and destination resolution logic in our calling infrastructure. As this coincided with some other changes in the same modules a decision was made to start separating that logic from the actual signaling logic as the later is highly stable (and needs to be very robust) while the former is liable to change much more often.

At the same time, our developers sought to standardize communication (and load balancing, redundancy, configuration management etc. issues that come with it) between separately deployed components and stuck with ICE. So, keen to play around with the new technology, they conducted some tests and a decision was made to use it for the newly created lump of business logic.

Historically, most of our business logic has resided within our databases. Not a bad decision at all given the horizontal and vertical splitting technology plus Postgres know-how we have in-house. However, this also meant that most of the knowledge of billing and routing internals resided with people who knew databases and were not about to start writing C++ code overnight, especially when it usually did not make any sense to ship data to a remote component for decision-making.

As a result, we ended up with a fairly slim layer of logic between the calling infrastructure and the database that, at the first glimpse, did very little but call a bunch of stored procedures. Of course, come time to deploy the thing, our operations people came asking why the heck they needed to support (and make highly available) an additional component that didn't add any value at all. Which was the rebellion at the beginning of the story.

So we discussed. And ended up with an understanding that in terms of design, developers still find value in that layer as the decision _which_ procedures to call is quite significant. Also, the data structures that get passed between it and the calling infrastructure are complex and it would be unwise to build serialization into flat structures required by the database into all of the calling systems. Some of the supportability concerns (but not all) the ops guys had could actually be solved quite easily, too. No major change in the architecture, then.

The reason I'm writing about this event is that there are several very important conclusions to draw from this event

• Your architectural decisions should take into account the organization you operate with. In some other situation, the very idea of moving logic from a middleware layer to a database would have been pure lunacy (most of the organizations struggle to do the opposite) but given the stuff our DBAs pull of on a regular basis it's not that bad
• Challenges are valuable, regular ones are even better. No design decision should be cast to stone, no concept should be considered OK only because "this is the way things are done". Although, most of the cases you still end up retaining the original idea, sometimes you don't. And this is where architectural evolution happens
• Work closely with the operations people. They provide very good reality check. Helps with deployment griefs, too
  

On re-use

Here's a situation for you. You have an information system that runs a substantial internet-based service. That service has web-based interfaces to it for billing and self-service purposes. Now, imagine, that there is a need to branch out, to build the services into different channels. For example, have one application that can fit into the client, one that works on regular browsers, one that is targeted with people with bad eyesight and one that works on handheld devices.

So the question is: how mych of the original web offering can you re-use? It is obvious, that all of the business logic like billing, core provisioning and customer management services need to be re-used, that's a no-brainer. But what about the application and presentation layers? The presentation layer is also quite trivial as the various new versions are meant for different devices and audiences they clearly need a different way to manifest themselves.

The application logic is the one that will cause you trouble. Let's stop pretending that we are talking about a random company here and admit that this is Skype. For example, the purchase flow of purchasing a SkypeIn number, is a very complex beast with tailored integration points for different countries, various ways to pick out the numbers etc. So how would one re-use that?

One way to do it was to use the same application logic everywhere and just re-skin it into WAP or slightly more compact HTML for various distribution channels. This, however, does not work, because different devices tend to have different requirements towards the page flow (which is a manifestation of the application logic), too. For WAP for example, you probably want to generate most of the pages into a deck from one requrest so you don't have to go back to the server every time user clicks "next". For the client-based version you probably want to ignore several corner cases and make the flow a couple of pages shorter. And so forth.

The other would be to re-write the whole thing and build a semi-intelligent fourth tier in place that can handle the workflow, decide when and how to talk to integration partners, give out number pools etc. This would work, but it adds additional layer of complexity, the existing stuff has to be re-written (re-writing something for technical reasons is always a bad idea) and there is no guarantee that this thing would actually contain any useful logic after you are done. Close, but no cigar.

Instead of these options, I'd say just take a deep breath and do not re-use. Lot's of people will not go "no, no, no! You will get yourself into a world of pain every time a common piece of logic changes as you need to go and make a change in all of those flows and you will surely forget something". In my mind, it is much worse to make a major business logic change without explicitly going over all the places that use it. And if you are already doing that, you might as well implement the change right there. Application logic is a combination of delivery channel requirements and business logic so any change to the latter is going to have an impact on the application logic that is specific to the channel. Meaning, that you would most probably go and tweak all the flows anyway. And if you forget any, you will be in trouble either way.

In summary: do not break your head about re-use. In case of the application logic, you sometimes need to gather your courage and not re-use at all.

Metaphor: drawing a horse

I found myself amid of a major discussion the other day. When defining the scope of a project, should one also state things that are _out_ of the scope? Some people said that this would lead to wishful thinking and describing the whole world in the "out of scope" section. The others said that everything _in_ scope could never be described in adequate detail anyway so describing the outer world is the only way to go. So I got into thinking (considering I also had to present on the issue), ended up with an analogy:

Say you wanted to draw a horse and did something like this (art lovers, look away now):
It ain't pretty, isn't it? One could also use a different approach:

Isn't going to win any prizes also. But combine the two:

And you get something that is still ugly but at least gives a sort of holistic view of the animal. So the point is that you need both the inside-out and outside-in perspectives on a project to get a sufficient understanding of its scope.

Go or nogo?

Whenever people make decisions on whether to go ahead with a project, they think if it makes business sense. Of course they do. What happens much more rarely is people thinking about how much sense it makes in terms of other architecture layers. The organizational architecture gets some attention but below that, it's all forgotten.

However, most of project/product failures come from the new stuff not fitting with the existing things in terms of functional, technical or support architecture. Of course, discrepancies there will mean changes to the original plan and can ultimately translated into dollars that end up in the business case, but wouldn't it be much cheaper to consider this in the beginning rather than all the way through the project?

This issue is also tied to the "10-minute-crap" problem: whenever people come up with an idea that is really easy to implement and makes some business sense they go "well, it does not bring massive business benefits but it's easy to do so let's just build it". Wrong. Because this is how you end up distorting all underlaying layers. Why would one do something stupid just because it takes very little effort?

To recap: go/no go decisions should be made by considering all the aspects of the project, not just the business top line.

Aspects of an Architect

My friend and colleague Sergei made a comment the other day after listening to a job interview that an architect should really have either some managerial experience or possess the potential to become one.

This is entirely true, I think. Being a leader or having the potential to become one would be even better. Drawing UML diagrams of Things to Be is just a tiny piece of the work an architect has to do. He or she also has to make sure people actually understand the drawings, has to tackle resistance in build or buy situations, guarantee preservation of knowledge if the project is put on hold or team members change and so on. All of this requires some managerial pedigree to be successful at. The thing is, that, believe it or not, the organizations are made of people and the computers are just there to help.

So next time at a job interview when you are asked how to choose between two major technologies, you better mention the skills of people around you in the answer.

Metaphor: Dripping water

It is said that the best way for a leader to communicate his or her vision, values and beliefs is through telling stories. This is also true for architects who, being engineers and pragmatic and all, tend to cut the stories short and turn them into metaphors that help to explain complex concepts to fellow engineers and also customers. XP is big on metaphors and I have found them useful, too. This is why this series is created: every now and then I stumble upon one that seems to work and convey an idea particularly well. Which means that it just might be worth sharing. Let's see how many of those I can come up with.

We had a team at Skype that struggled with incoming feature requests. They were short on resources and their importance in the business was growing rapidly. So everybody was busy throwing business ideas, feature requests, project proposals, bug reports at them to a point where most of the key people spent most of their time reviewing, estimating and designing solutions for them. Which, clearly, had to stop. This is not an uncommon problem and the obvious solution was to introduce a quantization mechanism that would allow to split the constant flow into manageable chunks. the only problem was that the customer did not want to wait, they wanted their thing to happen yesterday. Enter the Dripping Water Torture metaphor. Everybody has probably heard that at medieval times people were tortured with water dripping on their sculls for lengthy periods of time. Even the Mythbusers did an episode on it. This is how it feels being constantly bombarded with all sorts of functional requests.
Now imagine that instead of water dripping on your forehead and slowly driving you bonkers, a man with would turn up once a day and threw a bucket of cold water at you. Unpleasant as that might be, it's not much of a torture. The message was heard loud and clear and now there is at least an understanding of what we are trying to solve with the recent process changes.