50 lines
1.9 KiB
Markdown
50 lines
1.9 KiB
Markdown
---
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layout: pattern
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title: Saga
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folder: saga
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permalink: /patterns/saga/
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categories: Concurrency
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tags:
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- Cloud distributed
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---
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## Also known as
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This pattern has a similar goal with two-phase commit (XA transaction)
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## Intent
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This pattern is used in distributed services to perform a group of operations atomically.
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This is an analog of transaction in a database but in terms of microservices architecture this is executed
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in a distributed environment
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## Explanation
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A saga is a sequence of local transactions in a certain context. If one transaction fails for some reason,
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the saga executes compensating transactions(rollbacks) to undo the impact of the preceding transactions.
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There are two types of Saga:
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- Choreography-Based Saga.
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In this approach, there is no central orchestrator.
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Each service participating in the Saga performs their transaction and publish events.
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The other services act upon those events and perform their transactions.
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Also, they may or not publish other events based on the situation.
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- Orchestration-Based Saga
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In this approach, there is a Saga orchestrator that manages all the transactions and directs
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the participant services to execute local transactions based on events.
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This orchestrator can also be though of as a Saga Manager.
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## Class diagram
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## Applicability
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Use the Saga pattern, if:
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- you need to perform a group of operations related to different microservices atomically
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- you need to rollback changes in different places in case of failure one of the operation
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- you need to take care of data consistency in different places including different databases
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- you can not use 2PC(two phase commit)
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## Credits
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- [Pattern: Saga](https://microservices.io/patterns/data/saga.html)
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- [Saga distributed transactions pattern](https://docs.microsoft.com/en-us/azure/architecture/reference-architectures/saga/saga)
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