The Saga pattern is a design pattern used to manage and maintain data consistency across microservices in distributed transaction scenarios. It provides transaction management using a sequence of local transactions, where each local transaction updates the database and publishes a message or event to trigger the next local transaction in the saga. If a local transaction fails, the saga executes a series of compensating transactions that undo the changes made by the preceding local transactions. The Saga pattern is particularly useful for long-lived transactions that span multiple services or processes.
Some key features of the Saga pattern include:
- Compensating transactions: These are transactions that undo the changes made by preceding local transactions in the saga.
- Idempotency and retryability: Compensating transactions must be idempotent and retryable to ensure that transactions can be managed without manual intervention.
- Choreography and orchestration: There are two approaches to implementing the Saga pattern: choreography and orchestration. In choreography, each microservice that is part of the transaction publishes an event that is processed by the next microservice. In orchestration, a central coordinator manages the workflow of the transaction.
The Saga pattern is useful when an application needs to maintain data consistency across multiple microservices without tight coupling, and when there are long-lived transactions that could block other microservices if one microservice runs for a long time. However, the pattern is difficult to debug and its complexity increases with the number of microservices involved.
