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Comment by speedplane | Hacker News Reader

> microservices definitely make a host of issues harder ...

I agree with all the issues you've stated, but I'd like to add one more. Microservices arguably make it much easier to build systems with circulate dependencies leading to weird race conditions and deadlocks.

Consider two units of code A and B. If implemented as classes, modules, or libraries, it's relatively easy to spot and prevent A calling into B which in turn calls back to A. Sometimes the compiler and tools can automatically catch that.

With microservices, catching dangerous dependencies like this are much more difficult as each service, outwardly, seems independent of the other and there are few tools to catch these dependencies.

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There are few options, but what do you need beside a graph data structure?

We had a pipeline consisting of microservices and Kafka topics. Simple if/then logic quickly became problematic so I implemented our flow control as a directed acyclic graph, and it helped tremendously.

It's also easy to render your graph out with any number of visualization tools to quickly understand/validate work flows.

> There are few options, but what do you need beside a graph data structure?

I don't see how graph data structure solves this problem. Suppose you've created a photo sharing app. One microservice, A, has the graph database and stores the photos. One service, B, uploads and downloads photos. And a third service, C, applies filters to photos.

It's pretty easy to architect these services such that the download service B uses the filter service C in some situations, and the filter service C uses the download service B in others. This is obviously a bad design, but with microservices it's easier to make these bad design choices because the folks who wrote one service have little information about the other.

Sure, a graph wouldn't help fix that but it would at least illustrate the cyclic relationships and someone is hopefully recognizing the drawbacks inherent.

A tool to "fix" your example probably doesn't exist, but a graph is an excellent way to represent dependencies, reason about progress in the flow, and enforce constraints in a generic way.

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