code_orgnization_for_interservice_communication.md

Code Orgnization for Interservice Communication

• Command
  • Logic
  • Core Classes
• Event
  • Logic
  • Core Classes

Command

Logic

• Command is more like one service asks another service to do something.
• Each command channel belongs to a specific service for all the incoming command to that service (each command channel has only one consumer).
• Multiple services uses their proxy class to send command messages to a specific command channel (each command channel has one or more producer).

Core Classes

Class	Description	Example
Service	Defines the core operations for the service.	OrderService
Saga	Defines the Saga process for a specific operation. Each Saga process consists of multiples steps. Each step consists of a command and the info of which service to execute that command.	CreateOrderSaga
Commands Handler	Defines how to handle each command. Defines mapping relationship between the commands and the command handlers. Each command handler defines the operations need to be executed after receiving a specific command.	OrderServiceCommandHandlers

Event

Logic

• Event is more like one service notifies one or more other services about a change.
• Aggregate means the core entity of a specific service, like Order entity for the order service, Ticket entity for the kitchen service.
• One aggregate has one or more events belongs to the aggregate, like TicketCreatedEvent and TicketAcceptedEvent belong to Ticket aggregate.
• Each event channel belongs to a specific aggregate (each event channel has only one producer).
• Multiple services may listen to the same event channel (each event channel has one ore more consumer).
• One event may trigger multiple operations among multiple services simultaneously.

Core Classes

Class	Description	Example
Service	Defines the core operations for the service.	KitchenService
Domain Event Publisher	Publish all the events belongs to a specific aggregate.	TicketDomainEventPublisher
Event Consumer	Defines how to handle each event for a specific aggregate. Defines which aggregate it is listening. Defines mapping relationship between the events and the event handlers. Each event handler defines the operations need to be executed after getting a specific event.	KitchenServiceEventConsumer