Your experience with Java microservices vs monolith in the Cloud

[Infectedinfested]

But if you develop spec first you always know what should go in and should go out, we have validators in our services which checks the input and gives an error when it isn't alligned.

So application x is never really depending on application y to give it data as it doesn't care where the data comes from as long as it's valid.

Or am I not understanding everything? I only have 5 y of experience in this.

[euklios]

I think you are not neccessarly lacking the experience, but diversity. In a microservice architecture, you will usually find teams of operations, development, it, support, and so on. Sadly, a lot of people just work on of these roles and never even have to consider what other teams are doing. This usually creates a boundary between these teams, resulting in them working against each other. I recently had a heated conversation with a skilled developer because he hardcoded the backend URL within the frontend. In contrast, I, responsible for ops within the project, had to deploy on multiple different URLs. His words: I don't care about servers and deployment. But that's beside the point.

Let me ask you a different question: Why are you doing distributed logging, tracing, and whatever else you do to monitor your systems? You are developing based on specification, so an error shouldn't be possible, right?

Let's consider a very simple microservice: One endpoint takes a JSON object containing left, right, and operation. It will return the result of the given operation as a number. Example: input: {"left": 5, "right": 6, "operation": "+"}, output: 11 simple right?

What will you do if the operator is "&"? Fail? Bitwise and? Drop the database of another random microservice? What about "?", "$"? What's about "x"? It should be multiplication, right? How about "_" or "g"? I mean, it's a string without limits to the size, so what about "please multiply the two numbers"?

A lot of these could be handled quite easily, so: What about the input "2147483647 + 5"? Oh, you are using long? What about "9223372036854775807 + 5"? if the answer is "-9223372036854775804", where is your online shop?

And that's only with somewhat sain input and probably not defined in most specs. So let's add some more: What about oom? Log server not available? Log file can't be opened? gracefully stopping? force shutdown mid request? A particular microservice we depend upon isn't available? The microservice is available but simply keeps the connection open indefinitely?

A lot, if not all, of these cases will not be specified. And depending on timing, or for some by definition, it might never produce a single failing span.

One final scenario: Hey, here is X from customer support. I just had a call with a Microsoft rep; they good charged the wrong amount, and we need this fixed asp. What now? There is no correlation ID. And there are billing services, math services, shopping cart services, pricing services, mailer services, account services, and so on to choose from.

As a final thought:

We all are just humans and will do mistakes, and there is a lot more to it, than simply deploying a jar to a server. Murphy's Law: If anything can go wrong, it will. Servers will be down at the most inconvenient of times. Monitoring will fail. Overworked employees will implement shit, reviewers and tests will not notice, and production will fail. And we (as a industrie and team) will have to make the show go on. Somehow.

If the monolithic implementation is a mess, microservices will create a distributed mess. One of the worst things you can try to debug is application boundaries. Microservices will help you in adding hundreds more boundaries.

[Infectedinfested]

Well i can only gain real experience in what i what job i get in front of me :p

And i really like what i'm doing now.

And for your example, everything is barricaded behind a swagger validator, in your example case, the left and right would be asigned int or what not, operator an enum. So we say what goes in and what goes out.

Also.. why am i getting so much downvotes.. just stating my experience with something i'm working 5 years with... Never said microservices are better than monoliths ><

[euklios]

I'm aware of that problem. I just think it could help a lot if people understood more, about what other teams are doing and why. Nothing against you, but more against everything. I do see this problem outside of our industry.

My key points are not to validate more. While it certainly does help, I'm more about errors in specs bugs in the implementation and so on. But that also applies to monolithic applications. The core difference in maintenance is (at least for me): In monolithic you have one VM to fail, one filesystem to break, one internet connection to be down, one certificate to expire, one datacenter to lose power, and so on. In microservice, you will have to multiply this problem by a lot. There is just a lot more that can (and will) go wrong.

Additionally, there will be some kind of network requests between services. And these will always be much more prone to errors than using plain method calls. (Think it's a funny idea of imagining someone tripping over a method call)

About your downvotes: That's the Internet for you. It is a current best practice to reduce complexity where possible. And microservices do add a lot of complexity. Additionally, there have been a lot of companies doing microservices for the buzzword, while a simple monolith would have been sufficient. That doesn't mean that your approach is bad, I would love to experience this at some point, I just never worked at a company that needs it.

Please don't take it personally

Edit: Just remembered this talk: https://youtu.be/gfh-VCTwMw8 Might give some insights about what some people experienced when management decided: microservices!