Microservices.. yes, nowadays they are everywhere! In my previous post I’ve shared my thoughts that sometimes just a monolith can do the required task without being cut into microservices. But it is wonderful if microservices are the most suitable solution! This is definitely lovely!
First, we’ve got a lot of benefit it provides to us, second, we’ve got a great technology support to implement them – there are a lot of frameworks and platforms helping us develop some really good microservices.
The most of the conference talks I have recently seen are basically “Hello world” talks. The main message is “Hey, look how easy it is to create a microservice!”, “Just few annotations, and you are up and running!”. How great this is!
But when it comes to real life, most usually between start of the project till the first really useful microservice there is at least one sprint. More often three sprints. You’ll say – “That is ok! We are serious people doing serious enterprise!”. I still ask myself – “What can be so huge in one microservice, that it may require several weeks to be created?”. “Why then this service is called MICRO?”
I’m not sure if there is an official definition of a microservice, but a well-established idea is that it is a piece of software which is designed to perform only one single function, but in the best possible way. It should communicate with the rest of the world with the most lightweight protocol possible, like REST. So, if we have a login functionality, a microservice should be able to login a user in the most fast, easy, reliable, secure way. Only login and nothing else. For logout there should be another service. The size and complexity of such a service are not in scope of micro, they can be of any scale. Technically, there should be only one function exposed, but what happens under the curtains are just implementation detalils.
This is why, the most of such services become really complicated, often even overengineered. From my experience, at the end of the day, each microservice in enterprise webapps becomes a usual three-tier application. It has its “UI” simplified to REST endpoints, it has its business layer with several services interfaces and their implementations, an infrastructure layer to talk to DB and other services. The interlayer communication is done via value objects. As a result, a usual call of a function of this microservice ends up with several data coping from one value object to another (in one of such microservices I’ve seen up to 14 of such hops). Why would you do this? The typical answer is if some part of the service changes, we will change only this part of it. Fair enough. If in return I ask, how many times in your life have you ever changed one of the tiers without affecting the others? Тhe answer is usually – never.
Once again, nothing wrong here. The complexity of the implementation of a microservice is orthogonal to the interface it provides.
Another question: how many times have you ever received a fully functional “freezed” interface definition? The spec that never changes? A guaranteed never to change document? In my case – never!
The changes are coming constant or even increasing speed. Even in terms of one API version. You may say: You are doing it wrong! You should plan more carefully, you should rethink your spec versioning policy etc. And you will be completely wright!
But.. there is something called real life! There are business needs that require quick reaction, quick change, quick time to market!
Looks like this constant change is just inevitable. For my 13 years in software development there were practically no projects that had really smooth stable development. A least every sprint there were some “tiny” spec changes, causing all codebase to suddenly go red. I’m sure I’m not the only “lucky” having this.
How should we solve this kind of problems in the microservices world? Its quite time consuming to create beautiful, complex, nicely architectured, (at least) three-tier microservices without frozen spec. As I already said, those spec changes usually require changes in all of the layers. This is hard! Most of us thought that’s just the way it is. Software development is hard.
But this situation kept me bothering. May be there is a way to expedite this change reaction? May be a microservice should be micro in all aspects? I mean really tiny? With as less internal abstractions as possible? Really tight coupled inside? When I’m writing this, I have a feeling I’m breaking the law. It is like I’m cancelling everything I’ve learned from the CS courses in the university. Why don’t we throw away all of the … tiers? Make it a really tiny one-tied micro monolith? A microlith? So that the object or even a direct line with data we receive from the infrastructure we transform to JSON object in one single class? With all the business logic also included in this one and the same class? You are absolutely eligible to say – “are you nuts?” What if the infrastructure changes? What if the Rest API changes? What if the business logic changes? You have to rewrite everything!
And then I suddenly say – “Yes! We will rewrite this service from scratch!”. Luckily, a lot of code in the service can be just generated. So, yes. We will rewrite it from scratch! We copy/paste. We do all the possible anti patterns. Only to make it work according to the spec and pass the tests! “But isn’t it a lot of effort?”. My answer is – “Pretty much the same as changing all of the classes in all of the three (or more) tiers!”. And people usually say – “Hmm…”.
This may sound really strange, but through several last projects, writing some really ugly small one tier microservices with really almost no architecture and no refactoring, then rewriting this from scratch saved me a lot of efforts. I have even created a name for this piece of software – “Throwawayware!”. Try to say it quick!
The next question that usually comes is – “Do you put this ugly thing in production??”.
My answer is: – “Ok, you got me! No, this does not go to production! May be sometimes..”. What actually goes there?
Putting this ugly little thing in production will be just catastrophic. That’s why I’ve tried some mixed approach.
First of all, we usually develop the tests to follow the contract. Yep, although I’m not a big fan of TDD, I think this is a good place to use it. Adjusting the tests to follow the spec and the contract is always the first priority to us!
Then we usually have 4 to 10 iterations on each microservice in this ridiculous “throw away” way. Funny thing is that up to 50% of the services do not even survive through those iterations! At some point the service may come obsolete even before production. This means that we usually save a lot of efforts for not creating something complex for something that will never be used (“Bingo!”).
Then when the service gets through those several iterations, we consider this service as “survivor”. At this time usually, the spec stabiles as well. And we do the same for each API version.
Just like the Garbage collector in JVM.. Haha! Yep, like the GC! Lovely!
For the survivors we usually make some really complex refactoring, or rewriting it completely new. We try to make their code really readable, expandable and maintainable. Quite often from the usage of those “throw away” implementations we can see some before unpredicted usage cases, like for example the pressure it should hold, or security, or fault times etc. This may end in three-tier architecture, but with really nicely designed layers.
Looks like this “two stages approach” works really well! Funny thing is that it fits perfectly in our SCRUM cycle. May be, I’m wrong, but this approach saved us a lot of effots and helped us establish good quality implementations in shorter time. In three projects so far.. We’ll see how it goes!
Any critic is welcome though…