问题说明：项目中有一个场景需要对界面进行登录验证。 获取请求的head的相关信息并验证当前用户是否已登录。 但是，接口中有调用的下游接口也有类似的验证。 在这种情况下，必须将请求的head信息传递到下游接口。 在网上搜索相关问题可以找到以下方案。
@ componentpublicclassfeignrequestinterceptorimplementsrequestinterceptor { @ overridepublicvoidapply (请求模板请求程序请求程序) butes=(servletrequestattributes ) requestcontextholder.getrequest attributes (； 属性！=null (httpservletrequestrequest=attributes.getrequest )； enumerationstringheadernames=request.get header names (； if(headernames！=null () while (headernames.hasmoreelements ) ) string name=headernames.nextelement )； string values=request.get header (name； requesttemplate.header(name，values )； }}}}}创建从当前请求中获取头部信息并将其放入请求模板的Feign阻止程序。 但是，这样写下来，我们发现attributes无法在空(requestcontextholder.getrequest attributes () )中检索请求。
原因分析：调试程序检查相关代码后，当代码到达拦截器时，当前线程是以“hystrix-”开头的线程名称，而不是http线程池中的线程。 从RequestContextHolder检索request时，从ThreadLocal检索，因此即使线程发生变化，当然也无法取得的线程是以' hystrix-'开头的线程名称，因此已打开熔断尝试在internet上搜索信息时，打开熔断后，feign调用将根据hystrix的默认并发策略在另一个线程池中运行。
解决方案：解决方案有三种。
1、关闭hystrix
更改配置
feign.hystrix.enabled=false直接关闭hystrix当然可以解决，但显然不合适
2、将hystrix并发策略设置为信号模式
添加配置
hy strix.com mand.default.execution.isolation.strategy=semaphore信号是指每个FeignClient，而不是单独为每个FeignClient分配线程池http线程池会影响性能，特别是在下游接口响应较差的情况下。
3、定制hystrix并发战略
继承HystrixConcurrencyStrategy类，编写wrapCallable方法以在callable之外获取RequestContextHolder上下文信息，然后传递给callable以设置相应的上下文环境由于RequestContextHolder中的request可能会被http线程释放，因此建议您创建自己的ContextHolder来单独放置head信息。
这里会出现另一个问题。 因为只有一个HystrixConcurrencyStrategy，所以写一个简单的HystrixConcurrencyStrategy注册到HystrixPlugins后，可能会引入Spring Security等依赖关系进行覆盖因此，我参考Spring Security编写的securitycontextconcurrencystrategy，内部判断目前已经存在的HystrixConcurrencyStrategy，在已经存在的基础上包装，多个hystrixconcurrencystratencystrategy
为我改写的代码：
publicclassrequestheaderhystrixconcurrencystrategyextendshystrixconcurrencystrategyextencystrategy { privatefinalhystrixconcuration publicrequestheaderhystrixconcurrencystrategy (hystrixconcurrencystrategyexistingconcurrencystrategy ) this.existingconcurcuct
c BlockingQueue<Runnable> getBlockingQueue(int maxQueueSize) {return existingConcurrencyStrategy != null ? existingConcurrencyStrategy.getBlockingQueue(maxQueueSize) : super.getBlockingQueue(maxQueueSize);}@Overridepublic <T> HystrixRequestVariable<T> getRequestVariable(HystrixRequestVariableLifecycle<T> rv) {return existingConcurrencyStrategy != null ? existingConcurrencyStrategy.getRequestVariable(rv) : super.getRequestVariable(rv);}@Overridepublic ThreadPoolExecutor getThreadPool(HystrixThreadPoolKey threadPoolKey, HystrixProperty<Integer> corePoolSize, HystrixProperty<Integer> maximumPoolSize,HystrixProperty<Integer> keepAliveTime, TimeUnit unit, BlockingQueue<Runnable> workQueue) {return existingConcurrencyStrategy != null ?existingConcurrencyStrategy.getThreadPool(threadPoolKey, corePoolSize, maximumPoolSize, keepAliveTime, unit, workQueue) :super.getThreadPool(threadPoolKey, corePoolSize, maximumPoolSize, keepAliveTime, unit, workQueue);}@Overridepublic ThreadPoolExecutor getThreadPool(HystrixThreadPoolKey threadPoolKey, HystrixThreadPoolProperties threadPoolProperties) {return existingConcurrencyStrategy != null ?existingConcurrencyStrategy.getThreadPool(threadPoolKey, threadPoolProperties) :super.getThreadPool(threadPoolKey, threadPoolProperties);}@Overridepublic <T> Callable<T> wrapCallable(Callable<T> callable) {Map<String, String> headers = AuthenticationContextHolder.getRequestHeaders();SysUser userInfo = AuthenticationContextHolder.getUserInfo();return existingConcurrencyStrategy != null ?existingConcurrencyStrategy.wrapCallable(new WrappedCallable<T>(callable, headers, userInfo)) :super.wrapCallable(new WrappedCallable<T>(callable, headers, userInfo));}static class WrappedCallable<T> implements Callable<T> {private final Callable<T> callable;private final Map<String, String> headers;private final SysUser userInfo;public WrappedCallable(Callable<T> callable, Map<String, String> headers, SysUser userInfo) {this.callable = callable;this.headers = headers;this.userInfo = userInfo;}@Overridepublic T call() throws Exception {try {AuthenticationContextHolder.setRequestHeaders(headers);AuthenticationContextHolder.setUserInfo(userInfo);return callable.call();} finally {AuthenticationContextHolder.remove();}}}}@Configuration(proxyBeanMethods = false)@ConditionalOnProperty(name = "feign.hystrix.enabled", havingValue = "true")@Slf4jpublic class HystrixConcurrencyStrategyAutoConfiguration {@Autowired(required = false)private HystrixConcurrencyStrategy existingConcurrencyStrategy;@PostConstructpublic void init() {HystrixEventNotifier eventNotifier = HystrixPlugins.getInstance().getEventNotifier();HystrixMetricsPublisher metricsPublisher = HystrixPlugins.getInstance().getMetricsPublisher();HystrixPropertiesStrategy propertiesStrategy = HystrixPlugins.getInstance().getPropertiesStrategy();HystrixCommandExecutionHook commandExecutionHook = HystrixPlugins.getInstance().getCommandExecutionHook();HystrixConcurrencyStrategy concurrencyStrategy = detectRegisteredConcurrencyStrategy();HystrixPlugins.reset();// 注册Hystrix并发策略以外的插件HystrixPlugins.getInstance().registerConcurrencyStrategy(new RequestHeaderHystrixConcurrencyStrategy(concurrencyStrategy));HystrixPlugins.getInstance().registerEventNotifier(eventNotifier);HystrixPlugins.getInstance().registerMetricsPublisher(metricsPublisher);HystrixPlugins.getInstance().registerPropertiesStrategy(propertiesStrategy);HystrixPlugins.getInstance().registerCommandExecutionHook(commandExecutionHook);}private HystrixConcurrencyStrategy detectRegisteredConcurrencyStrategy() {HystrixConcurrencyStrategy registeredStrategy = HystrixPlugins.getInstance().getConcurrencyStrategy();if (existingConcurrencyStrategy == null) {return registeredStrategy;}if (registeredStrategy instanceof HystrixConcurrencyStrategyDefault) {return existingConcurrencyStrategy;}if (!existingConcurrencyStrategy.equals(registeredStrategy)) {log.warn("找到多个 HystrixConcurrencyStrategy， 使用已存在的HystrixConcurrencyStrategy");}return existingConcurrencyStrategy;}}@Componentpublic class FeignRequestInterceptor implements RequestInterceptor {@Overridepublic void apply(RequestTemplate requestTemplate) {ServletRequestAttributes attributes = (ServletRequestAttributes) RequestContextHolder.getRequestAttributes();if (attributes != null) {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);}}} else {// RequestContextHolder中获取不到request时，可能是当前线程在Hystrix线程池中，则需要从AuthenticationontextHolder中获取header信息Map<String, String> headers = AuthenticationContextHolder.getRequestHeaders();if (MapUtils.isNotEmpty(headers)) {headers.forEach(requestTemplate::header);}}}}其中HystrixConcurrencyStrategyAutoConfiguration类中加了条件注解，在关闭hystrix的时候就不需要装配自定义的并发策略了
参考：https://www.codenong.com/cs109642312/