SAGA Pattern using apache camel in Spring Boot

The Saga pattern is a design pattern used for handling distributed transactions that involve multiple microservices. In the Saga pattern, a long-running transaction is broken down into smaller, more manageable transactions that are executed by different microservices. Each transaction in the Saga represents a step in the overall transaction, and if any step fails, the Saga can be rolled back to its previous state.

Apache Camel is a powerful integration framework that provides support for implementing the Saga pattern in Spring Boot applications. Here's an example of how to implement the Saga pattern using Apache Camel in Spring Boot:

1. First, you need to add the Apache Camel and Spring Boot dependencies to your project:

    <dependency>
        <groupId>org.apache.camel</groupId>
        <artifactId>camel-spring-boot-starter</artifactId>
        <version>x.x.x</version>
    </dependency>
    <dependency>
        <groupId>org.apache.camel</groupId>
        <artifactId>camel-saga</artifactId>
        <version>x.x.x</version>
    </dependency>
   

1. Next, you can define your Saga using Camel's Saga DSL. In this example, we will create a Saga that involves three microservices: Order Service, Payment Service, and Shipping Service. Each service is responsible for a single step in the transaction:

    @Component
    public class OrderSaga {
   
        @Autowired
        private OrderService orderService;
   
        @Autowired
        private PaymentService paymentService;
   
        @Autowired
        private ShippingService shippingService;
   
        @Saga
        public void processOrder(String orderId) {
            Order order = orderService.getOrder(orderId);
   
            // Step 1: Reserve the order
            boolean orderReserved = orderService.reserveOrder(orderId);
   
            // Step 2: Process payment
            boolean paymentProcessed = paymentService.processPayment(orderId, order.getTotalAmount());
   
            // Step 3: Ship the order
            boolean orderShipped = shippingService.shipOrder(orderId);
   
            if (!orderReserved || !paymentProcessed || !orderShipped) {
                // If any step fails, roll back the transaction
                throw new RuntimeException("Failed to process order");
            }
        }
    }
   

1. Finally, you can use Camel's RouteBuilder to define the routes that will trigger the Saga:

    @Component
    public class OrderRoute extends RouteBuilder {
   
        @Autowired
        private OrderSaga orderSaga;
   
        @Override
        public void configure() throws Exception {
            from("direct:processOrder")
                .saga()
                .option("orderId", header("orderId"))
                .compensation("direct:cancelOrder")
                .completion("direct:completeOrder")
                .to("bean:orderSaga?method=processOrder");
   
            from("direct:cancelOrder")
                .bean(OrderService.class, "cancelOrder(${header.orderId})");
   
            from("direct:completeOrder")
                .bean(OrderService.class, "completeOrder(${header.orderId})");
        }
    }
   

   In this example, the "direct:processOrder" route triggers the Saga and passes the orderId as a header. The "saga" component is used to wrap the route in a Saga, and the "option" method is used to store the orderId as a Saga option. The "compensation" and "completion" methods are used to define the routes that will be executed in case of a rollback or a successful completion of the Saga, respectively. Finally, the route calls the "processOrder" method of the OrderSaga bean, which executes the three steps of the Saga.

   That's a simple example of how to implement the Saga pattern using Apache Camel in Spring Boot. Of course, in a real-world scenario, you would need to handle more complex transactions and handle exceptions and retries

SAGA Pattern simple example:

Ref https://www.vinsguru.com/orchestration-saga-pattern-with-spring-boot/