Saga Pattern
Manage distributed transactions across multiple microservices using compensating actions to maintain data consistency.
Pattern Overview
The Saga pattern is a sequence of local transactions where each transaction updates data within a single service. Each local transaction publishes an event that triggers the next local transaction in the saga. If a local transaction fails, the saga executes a series of compensating transactions that undo changes made by preceding local transactions.
When to Use
- • Long-running business processes
- • Distributed transactions across services
- • When eventual consistency is acceptable
- • Complex business workflows
When Not to Use
- • When strong consistency is required
- • Simple CRUD operations
- • Single service transactions
- • Real-time financial transactions
System Architecture
The saga pattern orchestrates multiple microservices to complete a business transaction. Each service maintains its own data consistency while the saga coordinator manages the overall flow and handles failures.
Saga Flow
The saga executes steps sequentially, with each step potentially triggering compensation if subsequent steps fail. This ensures that the system can recover from partial failures.
Data Model
The data model tracks saga state, individual step execution, and compensation actions to ensure proper transaction management and recovery.
Implementation Example
A typical implementation includes a saga coordinator that manages the overall flow, step executors for individual services, and compensation handlers for rollback operations.
Benefits
- Maintains data consistency across services
- Handles partial failures gracefully
- Supports long-running transactions
- Enables complex business workflows
Trade-offs
- Complex compensation logic
- Difficult to debug and monitor
- Potential for infinite compensation loops
- Eventual consistency challenges
Best Practices
Design Principles
- • Keep sagas as short as possible
- • Design idempotent operations
- • Use event sourcing for audit trails
- • Implement proper error handling
Implementation Tips
- • Use saga coordinator pattern
- • Implement proper state management
- • Add comprehensive logging
- • Test failure scenarios thoroughly