Saga Pattern in-depth analysis. Convert a monolithic architecture to microservice architecture analysis. Why need orchestration in-depth analysis. Rollback mechanism of SAGA how work. These covered in this slide.

1. Journey of SAGA pattern
in Micro-service
Architecture
Presented by Anisur Rahman
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2. Refactoring Monolith to Micro-services
 Two refactoring strategies:
 Strategy 1: Implement new functionality as services
 Strategy 2: Extract services from the monolith
5 Steps:
 Step 0: Review AS-IS code
 Step 1: Split the code
 Step 2: Split the database
 Step 3: Define a standalone “Delivery service”
 Step 4: Use the standalone “Delivery service”
 Step 5: Remove the delivery management functionality from
the FTGO monolith
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3. Strategy 1: Implement new functionality as services
Story
Micro
Service
Micro
Service
Micro
Service
Database
Database
Database
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4. Strategy 2: Extract services from the monolith
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5. Review codebase, client-
domain interaction, database
Step 0: Review Monolith code
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6. Step 1: Split the code
Convert delivery management into a separate, loosely coupled module within the monolith
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7. Step 2: Split the database
Split the database and define a separate database schema for the Delivery service module
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8. Step 3: Define a standalone “Delivery service”
Just define a standalone service but don’t use it
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9. Step 4: Use the standalone “Delivery service”
Start using that standalone service
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10. Step 5: Remove the delivery management functionality from the FTGO
monolith Remove Delivery related code from Order Management Service
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11. Maintain data consistency in Micro service
Architecture
2PC Event Sourcing SAGA
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12. Need to know ACID transaction before
SAGA (recap)
 Atomicity: Transaction either completes fully or fails
completely.
 Consistency: Maintain the logical consistency, no matter
of its final outcome.
 Isolation: Multiple transactions occur concurrently
without causing inconsistency of database state
 Durability: Durability means that committed transactions
remain committed irrespective of any type of system
failure.
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13. What is SAGA?
 A pattern that maintain data consistency across services
using a sequence of local transactions that are
coordinated using asynchronous messaging.
 Maintain data consistency
 Sequence of local transactions.
 Each local transaction updates data within a single
service using the ACD transactions.
 Asynchronous messaging occur in SAGA
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14. SAGA
Lets see an example to understand the SAGA pattern & its characteristics:
Make
Order
Create
Order
Update
inventory
Regular
shopping
Return
Order Status
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15. SAGA implementation
 2 ways are most popular to implement SAGA:
 SAGA — Choreography
 Event based
 Each service communicate with each other via Message Broker
 SAGA — Orchestration
 Command based
 Orchestrator is own a service
 Each service communicate with Orchestrator
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16. SAGA - Choreography
Order Service
Inventory
Service
Shipping
Service
Inventory DB
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17. SAGA – Choreography - Rollback
Order Service
Inventory
Service
Shipping
Service
Inventory DB
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18. SAGA –
Orchestration
Inventory Service
Inventory DB
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19. Inventory Service
Inventory DB
SAGA –
Orchestration –
Rollback
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20. Really why you need Orchestration?
 3 main reasons I found through my R&D:
 A second transaction willing to change the same target object,
you can easily put it on hold on the orchestrator until the first
transaction ends. (Isolation problem solved)
 Easier rollback management
 Either I use Choreography OR Orchestration, I must have to create
a SEC. So, in Orchestration the Orchestrator act as a SEC. This
gives me more flexibility. SEC will maintain Audit log. If I use SEC
in Choreography then it will create a Event Sourcing Anti Pattern.
How can Choreography maintain Isolation?
 Use Counter measure design pattern: Semantic lock + Saga status
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21. When need to apply Rollback mechanism?
 Two type of error can occur through SAGA pattern:
 Technical Error:
 Reasons to occur: Database Connection Lost, Service down for any reason,
Code level Bug
 Solution: Use Message Broker for RETRY mechanism
 Business Error:
 Reasons to occur: Business rules violation
 Solution: Apply Compensate transactions
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22. Next Topic
Message Broker (RabbitMQ)
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23. Thank you
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