Spring Cloud Hystrix: circuit breaker and downgrade mechanism, protecting the cornerstone of application stability

php editor Youzi introduces to you Spring Cloud Hystrix, which is a circuit breaker and downgrade mechanism and is an important cornerstone to ensure application stability. Through Hystrix, applications can be effectively prevented from crashing due to external service failures, improving the flexibility and reliability of the system. Understanding and properly using Hystrix can help developers build more stable and reliable distributed systems and improve user experience.

Circuit breaker mechanism:

The circuit breaker mechanism is a fault-tolerant strategy. When a dependent service experiences a persistent failure, Hystrix will quickly disconnect and stop sending requests to the service. The advantage of doing this is:

• Avoid fault spread: Prevent faulty services from affecting other microservices.
• Protect resources: Release network connections and computing resources to the failed service.

Hystrix provides an annotation called Circuit Breaker, which can be applied to service methods. The sample code is as follows:

@CircuitBreaker(
commandKey = "UserService", // 命令键，用于标识熔断器实例
fallbackMethod = "getUserFallback" // 熔断时执行的降级方法
)
public User getUser(Long id) { ... }

Downgrade mechanism:

The downgrade mechanism is a fault-tolerant strategy. When the circuit breaker is open or a service exception occurs, Hystrix will perform a downgrade method and provide a simplified or backup service to ensure system availability.

Hystrix provides an annotation called Fallback, which can be applied to the downgrade method. The sample code is as follows:

public User getUserFallback(Long id) {
// 提供简化或备用的服务
return User.builder().name("Unknown").build();
}

Hystrix configuration:

Hystrix provides a series of configuration options that allow users to customize circuit breakers and degradation behaviors, including:

• Timeout: Request timeout. If this time is exceeded, the request is considered failed.
• Failure threshold: The threshold for the percentage of failed requests that the circuit breaker opens.
• Sleep time: The sleep time after the fuse is opened, during which no request will be sent.

These configurations can be set through properties files, Java code, or annotations.

Hystrix Monitoring:

Hystrix provides a wealth of monitoring indicators, including:

• Number of requests: The number of requests sent to dependent services.
• Request success rate: Percentage of successful requests.
• Failure rate: Percentage of failed requests.
• Fuse status: The current status of the fuse (closed, open, half-open).

These indicators can be visualized through monitoring tools such as Hystrix Dashboard or prometheus.

Applications:

Hystrix has a wide range of application scenarios in microservice architecture, such as:

• Database access: Prevent database failure from affecting other services.
• Remote service call: Response to slow response or unavailability of remote services.
• API Gateway: Cut down and downgrade external requests to ensure the stability of api.

By effectively applying spring Cloud Hystrix, the stability and availability of the microservice architecture can be significantly improved, providing users with a more reliable and consistent service experience.

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