What is SAGA Pattern?
The SAGA pattern, also known as distributed transaction management, is a design pattern used in distributed systems to manage long-running transactions that involve multiple services or components. In a distributed system, a single transaction may involve multiple microservices, each with its own database or storage system. The SAGA pattern helps to coordinate and manage these transactions across different microservices and ensures that the system remains consistent and reliable.
The SAGA pattern involves breaking a long-running transaction into smaller, more manageable steps, with each step represented as a separate transaction. Each transaction is responsible for either performing an action or undoing the action of a previous transaction. This makes it possible to coordinate and manage complex transactions that span multiple services and components.
For example, in an e-commerce system, a single transaction may involve creating an order, processing a payment, updating inventory, and shipping the order. If any of these steps fail, the entire transaction needs to be rolled back. The SAGA pattern can be used to coordinate and manage these steps across different microservices , ensuring that the transaction is completed successfully or rolled back if necessary.
An example order workflow might be:
Each step can be written as a Java class or function. For example, the “Prepare order” step might look like this:
This step includes a method named “prepareOrder” in a class named “OrderPreparationService” and performs the order preparation function.
Now, let’s connect these steps using the Saga design pattern:
Here we have a class named “OrderWorkflowService” and in its constructor we inject objects of other services named “OrderPreparationService”, “PaymentService”, “ShipmentService” and “DeliveryStatusService”. It has a method called “processOrder” which uses these services to call each step in turn. If an error occurs at any step, we call a method called “cancelOrder” to undo the action.
In this example, we can manage a complex workflow using the Saga design pattern, ensuring that customer orders are processed correctly.
The SAGA pattern is often implemented using asynchronous messaging systems such as Apache Kafka or RabbitMQ, which allow services to communicate and coordinate with each other in a distributed system.
Overall, the SAGA pattern is an effective way to manage distributed transactions and ensure the consistency and reliability of a distributed system.
“When you climb a great hill, you will see that there are many more hills to climb.” — Nelson Mandela