what is the difference between distributed computing, microservice and parallel computing
My basic understanding for:
Distributed computing is a model of connected nodes -from hardware perspective they share only network connection- and communicate through messages. each node code be responsible for one part of the business logic as in ERP system there is a node for hr, node for accounting. communication could be HTML, SOA, RCP
Microservice is a service that is responsible for one part of the business logic and communicate with each other usually by http. microservices could share the hardware resources and are accessed by thier api.
Parallel systems are systems which optimize the use of resources. for example multithreaded app running on several thread where sharing memory resources.
I am a little bit confused since microservices are distributed systems, but when running multiple microservices on single hardware resources they are also parallel systems. Am i getting it right here:
Answer
Micro services is one way to do distributed computing. There are many more distributed computing models like Map-Reduce and Bulk Synchronous Parallel.
However, as you pointed out, you don't need to use micro servers for a distributed system. You can put all your services on one machine. It's like using a screw driver to hammer a nail ;). Yeah, you'll have parallel computation on a single multi-core machine, but are micro services the right way to achieve it? They might be if you plan to move those services onto separate machines. However, if those services require co-location, then micro services was the wrong tool.
Distributed systems is one way to do parallel computing. There are many different ways to achieve parallel computation, like grid computing, multi-core machines, etc. Many of them are listed in the article I linked.