I’m confused. If a microservice doesn’t call the api of any other microservices, then when is sending the requests to any of them?
A large purpose of service oriented architecture is encapsulation. If no other microservices can make requests to your microservice, then you really haven’t encapsulated much.
I tend to think that the job of invoking the services lies within a gateway. For example, you can have a microservice for recipes, but a web gateway that know all of the various integrations necessary to generate a page. So the web gateway is essentially a monolith.
If and when you need to support mobile devices independently of your web UI, you can have a mobile gateway. Same idea. This gateway is optimized to know how to handle mobile traffic realities like smaller download sizes, etc.
I'm thinking this concept improperly conflates synchronous requests with eventually-consistent asynchrony.
No, you definitely don't want microservices making synchronous requests to other microservices and depending on them that way.
But it still may be necessary for your services to depend on each other, and that's where you can allow that communication through asynchronous eventually consistent communication. Actor communications, queue submission/consumption, caching, etc.
That is nice in theory and I agree it should be done wherever possible but lot of the time business logic will require immediate synchronous response to be returned as a next step in workflow will execute different branch of logic based on condition/result returned from previous microservice and the frontend / consumer / app will need immediate confirmation about whether action succeeded.
Even in such cases you might want to move bulk of processing to asynchronous queue based system but part of the logic might need to be executed synchronously (authorise credit card payment, you can process the payment asynchronously later, perhaps in bulk cron jobs like Apple Itunes does it but initial authorisation which decides whether purchase is successful must be synchronous).
Microservices is a back-end service pattern. MVC (Model View Controller) is a front-end pattern to enforce separation between data, UI and interaction logic.
A large purpose of service oriented architecture is encapsulation. If no other microservices can make requests to your microservice, then you really haven’t encapsulated much.