Spring Cloud Feign重试机制
Feign组件默认使用Ribbon的重试机制并增加了根据状态码判断重试机制，默认情况下是不启用的。Feign使用的是Spring Retry组件，需要引入依赖才能启用。
1、POM引入Spring Retry
org.springframework.retry
spring-retry
2、配置文件
eureka-client:
ribbon:
MaxAutoRetries: 1
MaxAutoRetriesNextServer: 1
retryableStatusCodes: 500,404
OkToRetryOnAllOperations: true
NFLoadBalancerRuleClassName: com.netflix.loadbalancer.AvailabilityFilteringRule #负载均衡规则
eureka-client 是自己的serverId，MaxAutoRetries同一台服务器上的最大重试次数（不包括第一次尝试），MaxAutoRetriesNextServer要重试的下一个服务器的最大数量（不包括第一个服务器），retryableStatusCodes可以根据接口返回的状态码判断是否重试其他服务，OkToRetryOnAllOperations只对所有的超时请求重试
注意： Ribbon的重试机制只有对GET请求或者设置了OkToRetryOnAllOperations生效 详情请查看源码：
public class RibbonLoadBalancedRetryPolicy implements LoadBalancedRetryPolicy {
...
public boolean canRetry(LoadBalancedRetryContext context) {
HttpMethod method = context.getRequest().getMethod();
return HttpMethod.GET == method || lbContext.isOkToRetryOnAllOperations();
}
...
}
Feign对返回状态码做了重试判断RetryableFeignLoadBalancer
public class RetryableFeignLoadBalancer extends FeignLoadBalancer
implements ServiceInstanceChooser {
...
[@Override](https://my.oschina.net/u/1162528)
public RibbonResponse execute(final RibbonRequest request,
IClientConfig configOverride) throws IOException {
...
if (retryPolicy != null
&& retryPolicy.retryableStatusCode(response.status())) {
byte[] byteArray = response.body() == null ? new byte[] {}
: StreamUtils
.copyToByteArray(response.body().asInputStream());
response.close();
throw new RibbonResponseStatusCodeException(
RetryableFeignLoadBalancer.this.clientName, response,
byteArray, request.getUri());
}
...
}
...
}
重试机制用的是Spring Retry组件当抛出异常时进行重试！
GET请求指的是feign client 请求其他client时声明的那个interface中mapping注解类型，RequestMapping不设置method默认为GET请求
@FeignClient("stores")
public interface StoreClient {
@RequestMapping(method = RequestMethod.GET, value = "/stores")
List getStores();
@RequestMapping(method = RequestMethod.POST, value = "/stores/{storeId}", consumes = "application/json")
Store update(@PathVariable("storeId") Long storeId, Store store);
}