解决Hystrix主线程结束，子线程拿不到request

在spring-cloud项目中：

Feign拦截器：

@Component
@Slf4j
public class FeignAccessTokenRequestInterceptor implements RequestInterceptor {
    @Override
    public void apply(RequestTemplate requestTemplate) {
        try {
            HttpSevletRequest request = ((ServletRequestAttributes)RequestContextHolder.currentRequestAttributes()).getRequest();
            requestTemplate.header("REQUEST-SOURCE", request.getHeader("REQUEST-SOURCE"));
        } catch (Exception e) {
            log.info("getRequest fail：{},ignore!", e.getMessage());
        }
    }
}

使用多线程异步调用微服务，在使用 RequestContextHolder.currentRequestAttributes()).getRequest()  来获取request信息，发现异步调用时，主线程结束后，子线程就获取不到request，会报以下错误信息。

getRequest fail：

No thread-bound request found: Are you referring to request attributes outside of an actual web request, or processing a request outside of the originally receiving thread? If you are actually operating within a web request and still receive this message, your code is probably running outside of DispatcherServlet/DispatcherPortlet: In this case, use RequestContextListener or RequestContextFilter to expose the current request。

解决思路：

1.将主线程的request和session信息放进ThreadLocal里，透传到子线程再去获取。

2.在开启新线程之前，将servletRequestAttributes设置为子线程共享
 

继承 HystrixConcurrencyStrategy ：

@Component
@Slf4j
public class RequestAttributeStrategy extends HystrixConcurrencyStrategy {

    public RequestAttributeStrategy() {
        HystrixPlugins.reset();
        HystrixPlugins.getInstance().registerConcurrencyStrategy(this);
    }

    @Override
    public <T> Callable<T> wrapCallable(Callable<T> callable) {
        RequestAttributes requestAttributes = RequestContextHolder.getRequestAttributes();
        return new WrappedCallable<>(callable, requestAttributes);
    }

    static class WrappedCallable<T> implements Callable<T> {

        private final Callable<T> target;
        private final RequestAttributes requestAttributes;

        public 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();
            }
        }
    }
}