Feign 和 Hytrix 在微服务上下游的请求头信息传递丢失问题

今天药忘吃喽~ 2022-12-25 06:55 187阅读 0赞

在 Spring Cloud 中 微服务之间的调用会用到Feign，但是在默认情况下，Feign 调用远程服务存在Header请求头丢失问题。

## 解决方案 ##

首先需要写一个 Feign请求拦截器，通过实现RequestInterceptor接口,完成对所有的Feign请求,传递请求头和请求参数。

### Feign 请求拦截器 ###

public class FeignBasicAuthRequestInterceptor implements RequestInterceptor { 
    
        private static final Logger logger = LoggerFactory.getLogger(FeignBasicAuthRequestInterceptor.class);
    
        @Override
        public void apply(RequestTemplate requestTemplate) { 
            ServletRequestAttributes attributes = (ServletRequestAttributes) RequestContextHolder
                    .getRequestAttributes();
            HttpServletRequest request = attributes.getRequest();
            Enumeration<String> headerNames = request.getHeaderNames();
            if (headerNames != null) { 
                while (headerNames.hasMoreElements()) { 
                    String name = headerNames.nextElement();
                    String values = request.getHeader(name);
                    requestTemplate.header(name, values);
                }
            }
            Enumeration<String> bodyNames = request.getParameterNames();
            StringBuffer body =new StringBuffer();
            if (bodyNames != null) { 
                while (bodyNames.hasMoreElements()) { 
                    String name = bodyNames.nextElement();
                    String values = request.getParameter(name);
                    body.append(name).append("=").append(values).append("&");
                }
            }
            if(body.length()!=0) { 
                body.deleteCharAt(body.length()-1);
                requestTemplate.body(body.toString());
                logger.info("feign interceptor body:{}",body.toString());
            }
        }
    }

配置 让所有 `FeignClient`，使用 `FeignBasicAuthRequestInterceptor`

feign:
      client:
        config:
          default:
            connectTimeout: 5000
            readTimeout: 5000
            loggerLevel: basic
            requestInterceptors: com.leparts.config.FeignBasicAuthRequestInterceptor

也可以配置让 某个 `FeignClient` 使用这个 `FeignBasicAuthRequestInterceptor`

feign:
      client:
        config:
          xxxx: # 远程服务名
            connectTimeout: 5000
            readTimeout: 5000
            loggerLevel: basic
            requestInterceptors: com.leparts.config.FeignBasicAuthRequestInterceptor

经过测试，上面的解决方案可以正常的使用；但是出现了新的问题。

在转发Feign的请求头的时候, 如果开启了Hystrix, Hystrix的默认隔离策略是Thread(线程隔离策略), 因此转发拦截器内是无法获取到请求的请求头信息的。

可以修改默认隔离策略为信号量模式：

hystrix.command.default.execution.isolation.strategy=SEMAPHORE

但信号量模式不是官方推荐的隔离策略;另一个解决方法就是自定义Hystrix的隔离策略。

### 自定义策略 ###

HystrixConcurrencyStrategy 是提供给开发者去自定义hystrix内部线程池及其队列，还提供了包装callable的方法，以及传递上下文变量的方法。所以可以继承了HystrixConcurrencyStrategy，用来实现了自己的并发策略。

@Component
    public class FeignHystrixConcurrencyStrategy extends HystrixConcurrencyStrategy { 
    
        private static final Logger log = LoggerFactory.getLogger(FeignHystrixConcurrencyStrategy.class);
    
        private HystrixConcurrencyStrategy delegate;
    
        public FeignHystrixConcurrencyStrategy() { 
            try { 
                this.delegate = HystrixPlugins.getInstance().getConcurrencyStrategy();
                if (this.delegate instanceof FeignHystrixConcurrencyStrategy) { 
                    // Welcome to singleton hell...
                    return;
                }
    
                HystrixCommandExecutionHook commandExecutionHook =
                        HystrixPlugins.getInstance().getCommandExecutionHook();
    
                HystrixEventNotifier eventNotifier = HystrixPlugins.getInstance().getEventNotifier();
                HystrixMetricsPublisher metricsPublisher = HystrixPlugins.getInstance().getMetricsPublisher();
                HystrixPropertiesStrategy propertiesStrategy =
                        HystrixPlugins.getInstance().getPropertiesStrategy();
                this.logCurrentStateOfHystrixPlugins(eventNotifier, metricsPublisher, propertiesStrategy);
    
                HystrixPlugins.reset();
                HystrixPlugins instance = HystrixPlugins.getInstance();
                instance.registerConcurrencyStrategy(this);
                instance.registerCommandExecutionHook(commandExecutionHook);
                instance.registerEventNotifier(eventNotifier);
                instance.registerMetricsPublisher(metricsPublisher);
                instance.registerPropertiesStrategy(propertiesStrategy);
            } catch (Exception e) { 
                log.error("Failed to register Sleuth Hystrix Concurrency Strategy", e);
            }
        }
    
        private void logCurrentStateOfHystrixPlugins(HystrixEventNotifier eventNotifier,
                                                     HystrixMetricsPublisher metricsPublisher,
                                                     HystrixPropertiesStrategy propertiesStrategy) { 
            if (log.isDebugEnabled()) { 
                log.debug("Current Hystrix plugins configuration is [" + "concurrencyStrategy ["
                        + this.delegate + "]," + "eventNotifier [" + eventNotifier + "]," + "metricPublisher ["
                        + metricsPublisher + "]," + "propertiesStrategy [" + propertiesStrategy + "]," + "]");
                log.debug("Registering Sleuth Hystrix Concurrency Strategy.");
            }
        }
    
        @Override
        public <T> Callable<T> wrapCallable(Callable<T> callable) { 
            RequestAttributes requestAttributes = RequestContextHolder.getRequestAttributes();
            return new WrappedCallable<>(callable, requestAttributes);
        }
    
        @Override
        public ThreadPoolExecutor getThreadPool(HystrixThreadPoolKey threadPoolKey,
                                                HystrixProperty<Integer> corePoolSize,
                                                HystrixProperty<Integer> maximumPoolSize,
                                                HystrixProperty<Integer> keepAliveTime,
                                                TimeUnit unit, BlockingQueue<Runnable> workQueue) { 
            return this.delegate.getThreadPool(threadPoolKey, corePoolSize, maximumPoolSize, keepAliveTime,
                    unit, workQueue);
        }
    
        @Override
        public ThreadPoolExecutor getThreadPool(HystrixThreadPoolKey threadPoolKey,
                                                HystrixThreadPoolProperties threadPoolProperties) { 
            return this.delegate.getThreadPool(threadPoolKey, threadPoolProperties);
        }
    
        @Override
        public BlockingQueue<Runnable> getBlockingQueue(int maxQueueSize) { 
            return this.delegate.getBlockingQueue(maxQueueSize);
        }
    
        @Override
        public <T> HystrixRequestVariable<T> getRequestVariable(HystrixRequestVariableLifecycle<T> rv) { 
            return this.delegate.getRequestVariable(rv);
        }
    
        static class WrappedCallable<T> implements Callable<T> { 
            private final Callable<T> target;
            private final RequestAttributes requestAttributes;
    
            WrappedCallable(Callable<T> target, RequestAttributes requestAttributes) { 
                this.target = target;
                this.requestAttributes = requestAttributes;
            }
    
            @Override
            public T call() throws Exception { 
                try { 
                    RequestContextHolder.setRequestAttributes(requestAttributes);
                    return target.call();
                } finally { 
                    RequestContextHolder.resetRequestAttributes();
                }
            }
        }
    }

致此，Feign调用丢失请求头的问题就解决的了 。