The Saga Pattern Explained: Managing Distributed Transactions in Microservices

This article was originally published on bmf-tech.com.

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.

References

• www.cs.cornell.edu - SAGAS
• microservices.io - Pattern: Saga
• qiita.com - The Dangers of Distributed Transactions When Migrating to Microservices
• qiita.com - Designing Transaction Management in Microservices (Preliminary Knowledge)
• zenn.dev - Implementing the Saga Pattern with AWS (Choreography Edition)
• learn.microsoft.com - Saga Distributed Transaction Pattern
• docs.aws.amazon.com - Saga Pattern
• wakatchi.dev - Summarizing Microservices Transactions with TCC and Saga Patterns
• eikatou.net - Learning the Distributed Transaction Saga Pattern
• techblog.raksul.com - Verification Using the Saga Pattern in Microservices
• www.techscore.com - Transactions in Microservices [Saga]
• www.12-technology.com - [SAGA Pattern] Advantages and Disadvantages of Choreography and Orchestration
• cloud.google.com - Implementing the Saga Pattern with Workflows
• medium.com - Microservices Saga Pattern on GCP
• www.oracle.com - The Reality of Transaction Management in Microservices Architecture
• speakerdeck.com - Suddenly Realizing It's a Saga Pattern!? Operating a Serverless Backend with a Small Team
• engineering.mercari.com - Distributed Transaction Management in Mercari Coin Payment Infrastructure