Description:
The Fallback design pattern is a resiliency pattern used in microservices architecture to handle failures gracefully. It ensures that when a service is unavailable or fails, the system can continue to operate by providing an alternative response or executing a predefined fallback mechanism. This pattern enhances the robustness and reliability of microservices by preventing cascading failures and improving the overall user experience.

Main Elements of the Pattern:

• Service Degradation: Provides a simplified version of the service or a cached response to maintain functionality.
• Fallback Handlers: Defines alternative methods or responses when the primary service call fails.
• Circuit Breaker Integration: Often used in conjunction with the Circuit Breaker pattern to monitor service health and redirect to fallback handlers when necessary.
• Timeout Management: Configures timeouts for service calls to ensure quick fallback execution.
• Resilience and Fault Tolerance: Enhances the system's ability to withstand failures without significant disruption.

References:

1. Microservices Patterns - Fallback
2. Spring Cloud Netflix - Hystrix Fallback
3. Resilient Microservices with Spring Boot and Hystrix
4. Java Design Patterns - Contribution Guidelines
5. Fallback pattern

Acceptance Criteria:

1. Implement a Fallback design pattern in the existing microservices architecture.
2. Ensure the primary service call and fallback handlers are properly defined and integrated.
3. Use a Circuit Breaker pattern to monitor the health of the primary service.
4. Configure timeouts for service calls to trigger fallback mechanisms promptly.
5. Provide unit and integration tests to validate the fallback functionality.
6. Document the implementation details and usage instructions in the project’s README file.