Java RPC框架熔断降级机制原理解析

<dependency>
  <groupId>com.netflix.hystrix</groupId>
  <artifactId>hystrix-core</artifactId>
  <version>${hystrix-version}</version>
</dependency>
<dependency>
  <groupId>com.netflix.hystrix</groupId>
  <artifactId>hystrix-metrics-event-stream</artifactId>
  <version>${hystrix-version}</version>
</dependency>

/**
 * 远程目标方法
 */
private Method method;

/**
 * 远程目标接口
 */
private Object obj;

/**
 * 远程方法所需要的参数
 */
private Object[] params;

/**
 * 远程接口客户端引用注解
 */
private RpcReference rpcReference;

/**
 * RPC客户端配置
 */
private ReferenceConfig referenceConfig;

public RpcHystrixCommand(Object obj, Method method, Object[] params, RpcReference rpcReference, ReferenceConfig referenceConfig)

super(Setter.withGroupKey(HystrixCommandGroupKey.Factory.asKey("CircuitBreakerRpcHystrixCommandGroup"))
            .andCommandKey(HystrixCommandKey.Factory.asKey("CircuitBreakerRpcHystrixCommandKey"))
            .andCommandPropertiesDefaults(
                HystrixCommandProperties.Setter()
                    .withCircuitBreakerEnabled(true)
                    .withCircuitBreakerRequestVolumeThreshold(1)
                    .withCircuitBreakerErrorThresholdPercentage(50)
                    .withCircuitBreakerSleepWindowInMilliseconds(5*1000)
                    .withMetricsRollingStatisticalWindowInMilliseconds(10*1000)
            )
            .andThreadPoolKey(HystrixThreadPoolKey.Factory.asKey("CircuitBreakerRpcHystrixCommandPool"))
            .andThreadPoolPropertiesDefaults(
                HystrixThreadPoolProperties.Setter().withCoreSize(100)
        )
    );

@Override
protected Object run() {
 // 执行远程调用
}

public @interface RpcReference {
  /**
   * 服务降级的伪装者类对象
   * @return
   */
  Class<?> fallbackServiceClazz() default Object.class;
}

protected Object getFallback() {

    Method[] methods = this.rpcReference.fallbackServiceClazz().getMethods();
    for (Method methodFallback : methods) {
      if(this.method.getName().equals(methodFallback.getName())){
        try {
          Object fallbackServiceMock= ApplicationContextUtils.getApplicationContext().getBean(this.rpcReference.fallbackServiceClazz());
          return methodFallback.invoke(fallbackServiceMock,this.params);
        } catch (IllegalAccessException e) {
          logger.error("RpcHystrixCommand.getFallback error",e);
        } catch (InvocationTargetException e) {
          logger.error("RpcHystrixCommand.getFallback error",e);
        }
      }
    }
    throw new RpcException("service fallback unimplement");
  }

@Override
public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {

  RpcHystrixCommand rpcHystrixCommand=new RpcHystrixCommand(proxy,method,args,this.reference,this.referenceConfig);
  return rpcHystrixCommand.execute();
}

@FeignClient(value = "JIM-CLOUD-PROVIDER-SERVER",fallback = ProductServiceHystrix.class)
public interface ProductService {
  @RequestMapping(value = "/product/{productId}",method = RequestMethod.GET)
  String getById(@PathVariable("productId") final long productId);

}

public interface ProductCommentMockService {
  Product getById(Long productId);
}

@Service
public class ProductCommentMockServiceImpl implements ProductCommentMockService {
  @Override
  public Product getById(Long productId) {

    Product mockProduct=new Product();
    mockProduct.setId(0L);
    mockProduct.setName("mock product name");

    return mockProduct;
  }
}

@RpcReference(
    maxExecutesCount = 1,
    fallbackServiceClazz = ProductCommentMockService.class
)
private ProductService productService;

{"id":0,"name":"mock product name"}