Overview

Notes on what I researched about the Saga pattern.

What is the Saga Pattern

In microservices, distributed transactions (such as 2phase commit) are not recommended
- The Saga pattern is used to ensure consistency while avoiding distributed transactions
Avoids long-term locks and uses eventual consistency
Compensating transactions
- Operations that cancel a series of transactions
- The Saga pattern prohibits simple rollbacks
Not a pattern unique to microservices, it was also used in SOA
Implementation patterns
- Choreography
  - Each service progresses the transaction with its own responsibility
  - Avoids SPOF, but makes overall testing difficult
- Orchestration
  - A central service is prepared to instruct each service to progress the transaction
  - Prone to SPOF, but makes overall testing easier
Software Architecture: The Hard Parts introduces eight types of Saga patterns

Other Patterns

Another pattern to maintain consistency in microservices, similar to the Saga pattern, is the TCC (Try-Confirm/Cancel) pattern, which also uses eventual consistency.

The TCC pattern is similar to 2phase commit, but in the TCC pattern, each service has three steps: preparation, confirmation, and cancellation of the transaction.

The TCC pattern does not perform rollbacks like compensating transactions, but ensures consistency by not performing processes that cause inconsistencies.