Everybody has probably heard about the much hyped word “Microservices”; the architecture that solves about everything as computers aren’t getting any faster (kind of) and the need for scaling and distribution is getting more important as more and more people are using the internet.
Don’t get me wrong, I love microservices! However, it is important to know that as with most stuff in the world, everything has tradeoffs.
Lessons to be Learned
I’ve been developing systems using microservices for quite a few years now, and there are alot of lessons learnt (and still lessons to be learned). I saw this presentation by Matt Ranney from Uber last year, where he talkes about the almost ridiculous amount of services Uber has, and the insight of all the problems that comes with communicating between all these independent and loosly coupled services. If you have ever developed asynchronous applications, you probably know what kind of complexity it might generate and how hard it can be to understand how everything sticks together. With microservices, this can be even harder.
The World of Computer Systems are Changing
I recognize many of the insights he shares from my experiences of building microservices. I recently did some developing using akka.net experiencing similar insights but on a whole new level. Microservices within microservices. I won’t jump off to that now, maybe I’ll share those thoughts at another occasion. However, microservice architectures today are getting more and more important. One reason is because the stagnation of hardware speed with cpus changing from the traditional one core where the clock frequency is increased between models to today where the cores instead are multiplied without the frequency increasing. But also because it gives you freedom as a developer when facing hugh applications and organisations. Also there is this thing called zero downtime. You might have heard of it. Everything has to work all the time.
Synchronisation
While I do tend to agree with most of what Matt says, I don’t agree with the being “blocked by other teams” statement. If you get “blocked” as a team, you are doing something wrong, especially if you are supposed to be microservice oriented.
Blocked tends to point towards you needing some sort of synchronisation of information, and before you have that you cannot continue. While synchronisation between systems must occur at some point, it does not mean that you cannot develop and release code that cannot be fully utilized until other systems have been developed and deployed. Remember agile, moving fast, autonomous, and everything has to work all the time? The synchronisation part is all about the mutable understanding of the contract between the services. When you have that, it’s just a matter of using different techniques to do parallell development without ever being blocked, like feature toggling. There need to be a “we are finished let’s integrate”-moment at some point, but it’s not a blockage per se. It’s all about continuation, and it is even more important with microservices as integration get’s more complex with more services and functionality being developed in parallel.
Context
Systems developed as microservices are also facing the problem of process context, or the start and end problem. As a user doing something you are usually seeing this doing as from a bubble perspective. You update a piece of information and expect to see a result from that action. But with microservice based systems, there might be alot of things going on at the same time during that action in many systems. The action does not necessary have the cause you think, and the context gets chopped in smaller pieces as your context now spans multiple systems. This leads to the distribution problem. How do you visualize and exaplain what’s happening when alot of things are happening at roughly the same time at different places? People tend to rely on synchronisation to explain things, but synchronisation is really hard to achive if you do not have all the context at the same time and place, which is next to impossible when it comes to parallelism, distribution, scaling, something you often get and want to have with microservices; asynchronicity. You might want to rethink the way you perceive the systems you are working with. Do you really need synchronisation, and why? It’s probably not an easy thing to just move away from as it is deep rooted in many peoples mind. A way to simplify actions happening. But things are seldom synchronous in the world, and as computers and systems are becoming more distributed, it will make less and less sense keeping it that way.
REST
I also think the overhyped use of the word REST might extend the problem. REST implies that model states is important. But many microservices are not always built around the concept of states and models. They want to continuesly change things. Transitions are really hard to represent as states. I’m not talking about what something transitioned TO but how to visualize the transition or the causation, the relationship between cause and effect. Sometimes functionality is best represented as functions and not the states before and after. Back are the days of RPC services. Why not represent an API as a stream of events? Stateless APIs! It’s all about watching things happen. Using commands and events can be a powerful thing.
Anyhow, microservices are great, but they might get you in situations where you feel confused as you try to apply things that used to work great but does not seem to fit anymore. By rethinking the way you percieve computer systems you will soon find new ways and it might give you great new possibilities. Dare to try new angles, and remember that it’s all about trade offs. Simulating the world exactly as is might not be feasible with a computer system, but still, treating it as a bounch of state models within a single process might not be the right way either.
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