feat(glossary): Add API Circuit Breaker.mdx (#2683)

apps/www/content/glossary/api-circuit-breaker.mdx

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+---
+title: "API Circuit Breaker: Best Practices Guide"
+description: Unlock API Circuit Breakers power. Learn from implementation examples. Explore Spring Boot and API Gateway integration.
+h1: "API Circuit Breaker: Best Practices"
+term: API Circuit Breaker
+categories: []
+takeaways:
+  tldr: A design pattern that prevents system failure by monitoring and managing service errors.
+  definitionAndStructure:
+    - key: Design Pattern
+      value: Fault Isolation
+    - key: Components
+      value: Monitor, Block, Fallback
+    - key: States
+      value: Closed, Open, Half-Open
+  historicalContext:
+    - key: Introduced
+      value: "2007"
+    - key: Origin
+      value: Distributed Systems (API Circuit Breaker)
+    - key: Evolution
+      value: Microservices API Circuit Breaker
+  usageInAPIs:
+    tags:
+      - Microservices
+      - Fault Tolerance
+      - Resilience
+    description: API Circuit Breaker is used in microservices architecture to prevent cascading failures by isolating faulty services. It monitors service errors, blocks further requests when a failure threshold is reached, and provides fallback responses to maintain system functionality.
+  bestPractices:
+    - Implement real-time monitoring to track service health and error rates.
+    - Configure appropriate thresholds for circuit states to manage transient issues.
+    - Establish fallback strategies to maintain service availability during failures.
+  recommendedReading:
+    - url: https://example.com/best-practices-circuit-breaker
+      title: Best Practices for Implementing Circuit Breaker Pattern in Microservices
+    - url: https://example.com/spring-cloud-circuit-breaker
+      title: "Micro Service Patterns: Best Practices for implementing Circuit Breaker with Spring Cloud"
+    - url: https://example.com/integration-applications-circuit-breaker
+      title: Circuit Breaker Pattern in Integration Applications
+  didYouKnow: The Circuit Breaker pattern was popularized by Michael Nygard's book 'Release It!' in 2007, where it was introduced as a strategy to prevent cascading failures in distributed systems.
+faq:
+  - answer: Implementing a circuit breaker involves several steps. First, initialize the circuit breaker with specific parameters such as timeout, failureThreshold, and retryTimePeriod. The circuit breaker starts in a closed state, allowing calls to pass through. If calls are successful, the state is reset. However, if failures exceed the defined threshold, the circuit breaker transitions to an open state, preventing further calls. This mechanism helps to prevent system overload and allows the failing service time to recover.
+    question: How to implement a circuit breaker?
+  - answer: An API Circuit Breaker is a software design pattern used primarily in distributed systems and microservices architectures. It enhances the reliability and fault tolerance of applications that interact with remote services or components over a network. The circuit breaker monitors the success or failure of requests to these services. If failures exceed a certain threshold, the circuit breaker trips, and further calls are blocked until a specified timeout period has passed, preventing system overload and allowing the failing service to recover.
+    question: What is a circuit breaker in API?
+  - answer: An example of implementing a circuit breaker in a microservice system can be seen in the RegistrationServiceProxy from the Microservices Example application. This component, written in Scala, uses a circuit breaker to handle failures when invoking a remote service. The @HystrixCommand annotation arranges for calls to the registerUser() function to be executed using a circuit breaker. If the remote service fails repeatedly, the circuit breaker trips, preventing further calls and allowing the service to recover.
+    question: What is an example of implementing a circuit breaker in a microservice system?
+  - answer: In the context of APIs, the basic operating principles of a circuit breaker involve monitoring the success or failure of network requests. When the circuit breaker is closed, requests pass through. If a request fails, the failure count increases. If this count exceeds a pre-defined threshold within a certain time period, the circuit breaker 'trips' and moves to the open state, blocking further requests. After a pre-defined timeout period, the circuit breaker enters a half-open state, allowing a limited number of test requests. If these succeed, the circuit breaker closes again; if they fail, it reopens.
+    question: What are the basic operating principles of a circuit breaker?
+updatedAt: 2024-11-25T19:08:32.000Z
+slug: api-circuit-breaker
+---
+
+API Circuit Breakers are a crucial design pattern in software development, particularly for enhancing system resilience in microservices architectures. They prevent cascading failures when calling remote services or APIs, ensuring that the overall system remains stable even in the face of errors. By detecting failures and encapsulating logic to prevent repeated failures, API Circuit Breakers play a vital role in maintaining the health of distributed systems.
+
+## Understanding API Circuit Breakers
+
+API Circuit Breakers operate similarly to electrical circuit breakers. They "trip" to halt operations when they detect a failure in the system. In the context of APIs, a circuit breaker monitors recent failures, and if they exceed a predefined threshold, it trips. Once tripped, the circuit breaker prevents further interactions with the failing service by returning a predefined response or executing a fallback action until the system recovers.
+
+## Best Practices for API Circuit Breakers
+
+To effectively implement an API Circuit Breaker, consider the following best practices:
+
+1. **Set Realistic Thresholds**: Establish failure rate thresholds based on historical data and anticipated traffic patterns to ensure optimal performance.
+2. **Implement Fallback Mechanisms**: Design effective fallback strategies to maintain functionality when a service is unavailable, enhancing user experience.
+3. **Monitor and Log Failures**: Continuously monitor service health and log failures to adjust thresholds and improve system resilience.
+4. **Test Circuit Breaker Behavior**: Regularly test the circuit breaker implementation under various failure scenarios to ensure it behaves as expected.
+5. **Gradual Recovery**: Utilize techniques like exponential backoff or incremental retry intervals to allow the system to recover gradually.
+
+## Implementing Circuit Breakers in Spring Boot
+
+For Spring Boot developers, implementing a circuit breaker is straightforward using the `resilience4j` library. Below is a practical example of how to integrate a circuit breaker with a RESTful service:
+
+```java
+import org.springframework.web.bind.annotation.GetMapping;
+import org.springframework.web.bind.annotation.RestController;
+import io.github.resilience4j.circuitbreaker.annotation.CircuitBreaker;
+
+@RestController
+public class ExampleController {
+
+    @GetMapping("/example")
+    @CircuitBreaker
+    public String exampleEndpoint() {
+        // Call to external service
+        return "Success Response";
+    }
+}
+```
+
+This example demonstrates how to use the resilience4j circuit breaker in a Spring Boot application, providing a simple yet effective way to manage failures.
+
+## Integrating Circuit Breakers with API Gateways
+
+Integrating circuit breakers at the API Gateway level allows for centralized management of circuit breaking policies, which is particularly beneficial in microservices architectures. This setup protects downstream services by preventing requests to unhealthy services. API Gateways like Kong, AWS API Gateway, or Azure API Management can be configured to include circuit breaker capabilities, ensuring uniform application of these policies across all managed APIs.
+
+## Rate Limiting with Spring Cloud API Gateway
+
+In addition to circuit breakers, Spring Cloud Gateway provides built-in support for rate limiting, which helps prevent API abuse and manage load on backend services. Rate limiting can be configured using various algorithms, with the Token Bucket algorithm being a common choice. Here’s an example of how to configure rate limiting in Spring Cloud API Gateway:
+
+```yaml
+spring:
+  cloud:
+    gateway:
+      routes:
+        - id: example_route
+          uri: http://example.com
+          filters:
+            - name: RequestRateLimiter
+              args:
+                redis-rate-limiter.replenishRate: 10
+                redis-rate-limiter.burstCapacity: 20
+```
+
+This configuration sets a limit of 10 requests per second, with a burst capacity of 20 requests, using Redis to maintain rate limiting counters.
+
+## Conclusion
+
+In summary, API Circuit Breakers are essential for building resilient microservices. By following best practices for implementation and integrating with API Gateways, developers can significantly enhance the stability and reliability of their applications. Whether you're looking for an API Circuit Breaker best practices and implementation example or a Spring Cloud Gateway circuit breaker example, understanding these concepts is vital for any API developer aiming to create robust systems.