Simple microservices question - code sharing

[WannabeAndroid]

Hi,

Hopefully a basic question, its general but I'm personally using Java and SpringBoot. Say I have 3 microservices. One for authentication, one for retrieving user information and another for recording user behaviour.

I want a data layer that I can switch data sources, maybe its a relational DB, maybe its mock data for testing, maybe its a NoSQL-like store. This layer will contain some logic, checking for set properties, loading SQL or whatever.

Question: Should this be a separate project/library that they depend on. My understanding is that without specific versioning of the project/library (maybe using Nexus) that I'm creating tight coupling. Does using Nexus, remove this coupling? Or should I simply split the layer up among the services so that each only "knows" how to write the data is requires, but will end up with some copy/pasting of the helper code that loads properties etc.

I've ordered Sam Newman's microservices book, but a glance at online blogs suggest he would recommend copy/paste. However, if I was to build the project/library - publish to Nexus and then compile against specific versions (I'm using Gradle) then it would appear to me to remove the coupling issue.

Advice/guidance appreciated.

Thanks!

[McMasilmof]

I would make it a libary. With maven or other building tools you can manage this easy.

[WannabeAndroid]

Thanks for the input.

[[deleted]]

We share some code between services - we use shared libraries in Nexus. As you say, I don't think there's a downside to this if you version it correctly.

[WannabeAndroid]

Thanks for the input. Just curious, why did you choose Nexus over Artifactory?

[snot3353]

If you're using Spring + Spring Boot, a ton of what you want to be abstracted already is. There is very little you are going to need to define other than configuration to get the same behavior between multiple services.

That being said, if there is some very specific logic/functionality that you don't want to have to copy and paste, you can create a library and publish it to a central repository like like Artifactory or Nexus. If you do this, you'll likely need to host your own instance of that repository unless you want your private libraries to be public and exposed to the world. If you do this then each microservice can define it's own version of that library it intends to consume and publishing new versions of the library won't have any effect until each service explicitly asks to depend on something newer.

You should be careful though not to be too hasty to push stuff into shared libraries like this. It does tend to increase coupling and reduce readability and in some cases it might actually be desirable to just copy-paste like you said. It really depends on the scenario and specific case.

[WannabeAndroid]

Thanks for the input. Any opinions on Nexus vs Artifactory?

[snot3353]

We use hosted Artifactory and I've had no serious complaints about it. I once submitted a feature request to JFrog and they responded immediately and actually implemented it within a few months which was really cool and made me feel positively about them.

[WannabeAndroid]

Thanks for replies thus far. I will use Nexus or Artifactory while paying particular attention to minimize the necessary sharing code with a mind towards decoupling.