Grpc microservice architecture implementation

Question

In a microservice architecture, is it advisable to have a centralized collection of proto files and have them as dependency for clients and servers? or have only 1 proto file per client and server?

Answer 1

If your organization uses a monolithic code base (i.e., all code is stored in one repository), I would strongly recommend to use the same file. The alternative is only to copy the file but then you have to keep all the versions in sync.

If you share protocol buffer file between the sender and the receiver, you can statically check that both the sender and the receiver use the same schema, especially if some new microservices will be written in a statically typed language (e.g., Java).

On the other hand, if you do not have a monolithic code base but instead have multiple repositories (e.g., one per microservice), then it is more cumbersome to share the protocol buffers file. What you can do is to put them in separate repositories that can be added as an dependency to microservices that need them. That is what I have seen in my previous company. We had multiple small API repositories for the schema.

So, if it is easy to use the same file, I would recommend to do so instead of creating copies. There may be situations, however, where it is more practical to copy them. The disadvantage is that you always have to apply a change at all copies. In best case, you know which files to update, then it is just tedious. In the worst case, you do not know which files to update, and your schema will get out of sync. Only when the code is released, you will find out.

Note that monolithic code base does not mean monolithic architecture. You can have microservices and still keep all the source code together in one repository. The famous example is, of course, Google. Google also heavily uses protocol buffers for their internal communication. I have not seen their source code, but I would be surprised if they do not share their protocol buffer files between services.