concept Create Order Saga in category microservice

This is an excerpt from Manning's book Microservices Patterns. Login to get full access to this book.

The example saga used throughout this chapter is the Create Order Saga, which is shown in figure 4.2. The Order Service implements the createOrder() operation using this saga. The saga’s first local transaction is initiated by the external request to create an order. The other five local transactions are each triggered by completion of the previous one.

Figure 4.6 shows the design of the orchestration-based version of the Create Order Saga. The saga is orchestrated by the CreateOrderSaga class, which invokes the saga participants using asynchronous request/response. This class keeps track of the process and sends command messages to saga participants, such as Kitchen Service and Consumer Service. The CreateOrderSaga class reads reply messages from its reply channel and then determines the next step, if any, in the saga.

Figure 4.6. Implementing the Create Order Saga using orchestration. Order Service implements a saga orchestrator, which invokes the saga participants using asynchronous request/response.

Order Service first creates an Order and a Create Order Saga orchestrator. After that, the flow for the happy path is as follows: