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Feign正确的使用姿势和性能优化注意事项

Feign正确的使用姿势和性能优化注意事项
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1. feign自定义Configuration和root 容器有效隔离。

  • 用@Configuration注解
  • 不能在主@ComponentScan (or @SpringBootApplication)范围内,从其包名上分离
  • 注意避免包扫描重叠,最好的方法是明确的指定包名

2. Spring Cloud Netflix 提供了默认的Bean类型:

  • Decoder feignDecoder: ResponseEntityDecoder (which wraps a SpringDecoder)
  • Encoder feignEncoder: SpringEncoder
  • Logger feignLogger: Slf4jLogger
  • Contract feignContract: SpringMvcContract
  • Feign.Builder feignBuilder: HystrixFeign.Builder

3. Spring Cloud Netflix没有提供默认值,但仍然可以在feign上下文配置中创建:

  • Logger.Level
  • Retryer
  • ErrorDecoder
  • Request.Options
  • Collection<RequestInterceptor>

4. 自定义feign的消息编码解码器:

不要在如下代码中getObject方法内new 对象,外部会频繁调用getObject方法。

    ObjectFactory<HttpMessageConverters> messageConvertersObjectFactory = new ObjectFactory<HttpMessageConverters>() {     @Override     public HttpMessageConverters getObject() throws BeansException {         return httpMessageConverters;     }     };

5. 注意测试环境和生产环境,注意正确使用feign日志级别。

6. apacheHttpclient或者其他client的正确配置:

  • apacheHttpclient自定义配置放在spring root context,不要在FeignContext,否则不会起作用。
  • apacheHttpclient 连接池配置合理地连接和其他参数

7. Feign配置

#Hystrix支持,如果为true,hystrix库必须在classpath中 feign.hystrix.enabled=false  #请求和响应GZIP压缩支持 feign.compression.request.enabled=true feign.compression.response.enabled=true #支持压缩的mime types feign.compression.request.enabled=true feign.compression.request.mime-types=text/xml,application/xml,application/json feign.compression.request.min-request-size=2048  # 日志支持 logging.level.project.user.UserClient: DEBUG

8. Logger.Level支持

必须为每一个Feign Client配置来告诉Feign如何输出日志,可选:

  • NONE, No logging (DEFAULT).
  • BASIC, Log only the request method and URL and the response status code and execution time.
  • HEADERS, Log the basic information along with request and response headers.
  • FULL, Log the headers, body, and metadata for both requests and responses.

9. FeignClient.fallback 正确的使用方法

配置的fallback class也必须在FeignClient Configuration中实例化,否则会报
java.lang.IllegalStateException: No fallback instance of type class异常。

例子:

    @FeignClient(name = "hello", fallback = HystrixClientFallback.class)     public interface HystrixClient {         @RequestMapping(method = RequestMethod.GET, value = "/hello")         Hello iFailSometimes();     }      public class HystrixClientFallback implements HystrixClient {         @Override         public Hello iFailSometimes() {             return new Hello("fallback");         }     }      @Configuration     public class FooConfiguration {         @Bean         @Scope("prototype")         public Feign.Builder feignBuilder() {             return Feign.builder();         }          @Bean         public HystrixClientFallback fb(){             return new HystrixClientFallback();         }      }

10. 使用Feign Client 和@RequestMapping时,注意事项

当前工程中有和Feign Client中一样的Endpoint时,Feign Client的类上不能用@RequestMapping注解否则,当前工程该endpoint http请求且使用accpet时会报404.

下面的例子:

有一个 Controller

@RestController @RequestMapping("/v1/card") public class IndexApi {      @PostMapping("balance")     @ResponseBody     public Info index() {         Info.Builder builder = new Info.Builder();         builder.withDetail("x", 2);         builder.withDetail("y", 2);         return builder.build();     } }

有一个Feign Client

@FeignClient(         name = "card",         url = "http://localhost:7913",         fallback = CardFeignClientFallback.class,         configuration = FeignClientConfiguration.class ) @RequestMapping(value = "/v1/card") public interface CardFeignClient {      @RequestMapping(value = "/balance", method = RequestMethod.POST, produces = MediaType.APPLICATION_JSON_VALUE)     Info info();  }

if @RequestMapping is used on class, when invoke http /v1/card/balance, like this :

如果 @RequestMapping注解被用在FeignClient类上,当像如下代码请求/v1/card/balance时,注意有Accept header:

Content-Type:application/json Accept:application/json  POST http://localhost:7913/v1/card/balance

那么会返回 404。

如果不包含Accept header时请求,则是OK:

Content-Type:application/json POST http://localhost:7913/v1/card/balance

或者像下面不在Feign Client上使用@RequestMapping注解,请求也是ok,无论是否包含Accept:

@FeignClient(         name = "card",         url = "http://localhost:7913",         fallback = CardFeignClientFallback.class,         configuration = FeignClientConfiguration.class )  public interface CardFeignClient {      @RequestMapping(value = "/v1/card/balance", method = RequestMethod.POST, produces = MediaType.APPLICATION_JSON_VALUE)     Info info();  }

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