need clarification on microservices

Question

I need some clarifications on microservices. 1) As I understand only choreography needs event sourcing and in choreography we use publish/subscribe pattern. Also we use program likes RabbitMQ to ensure communication between publisher and subscribers.

2) Orchestration does not use event sourcing. It uses observer pattern and directly communicate with observers. So it doesn't need bus/message brokers (like RabbitMQ). And to cooridante all process in orchestration we use mediator pattern.

Is that correct?

Answer 1

In microservice orchestration , a centralized approach is followed for execution of the decisions and control with help of orchestrator. The orchestrator has to communicate directly with respective service , wait for response and decide based on the response from and hence it is tightly coupled. It is more of synchronous approach with business logic predominantly in the orchestrator and it takes ownership for sequencing with respect to business logic. The orchestration approach typically follows a request/response type pattern whereby there are point-to-point connection between the services.

In, microservice choreography , a decentralized approach is followed whereby there is more liberty such that every microservice can execute their function independently , they are self-aware and it does not require any instruction from a centralized entity. It is more of asynchronous approach with business logic spread across the microservices, whereby every microservice shall listen to other service events and make it's own decision to perform an action or not. Accordingly, the choreography approach relies on a message broker (publish/subscribe) for communication between the microservices whereby each service shall be observing the events in the system and act on events autonomously.