我们都知道，在hystrix默认情况下，采用线程池的熔断方式，每个openfeign都有自己的线程，而这使得它无法获取主线程上的变量；现在有个现实的问题就是，当前端登录后，把token经过gateway传到服务A，服务A再调用服务B时，B是无法收到请求头里的token信息的；一种不太好的解决方案就是使用信号量的方式。

使用ThreadLocal存储变量

public class NextHttpHeader {

	static final InheritableThreadLocal<Map<String, String>> inheritableThreadLocal = new InheritableThreadLocal<>();
	public static void set(String key, String val) {
		if (inheritableThreadLocal.get() == null) {
			inheritableThreadLocal.set(MapUtils.<String, String>hashMapBuilder(8).put(key, val).build());
		} else {
			inheritableThreadLocal.get().put(key, val);
		}
	}

	public static String get(String key) {
		if (inheritableThreadLocal.get() == null) {
			return null;
		}
		return inheritableThreadLocal.get().get(key);
	}

	public static Set<String> get() {
		if (inheritableThreadLocal.get() == null) {
			return null;
		}
		return inheritableThreadLocal.get().keySet();
	}


}

继承HystrixConcurrencyStrategy抽象类，实现自己的赋值逻辑

public class RequestContextHystrixConcurrencyStrategy extends HystrixConcurrencyStrategy {

	public <T> Callable<T> wrapCallable(Callable<T> callable) {
		// 先包装一下要执行的任务，在这里把ThreadLocal的值取出来
		return new ThreadLocalCallable<T>(callable);
	}

	public static class ThreadLocalCallable<V> implements Callable<V> {

		private Callable<V> target;

		private Map<String, String> dic = new HashMap<>();

		public ThreadLocalCallable(Callable<V> target) {
			this.target = target;
			NextHttpHeader.get().forEach(o -> {
				this.dic.put(o, NextHttpHeader.get(o));
			});
		}

		@Override
		public V call() throws Exception {
			this.dic.keySet().forEach(o -> {
				NextHttpHeader.set(o, this.dic.get(o));
			});
			return target.call();
		}

	}

}

@Configuration
@Slf4j
public class HystrixCircuitBreakerConfiguration {

	@PostConstruct
	public void init() {
		HystrixPlugins.getInstance().registerConcurrencyStrategy(new RequestContextHystrixConcurrencyStrategy());
	}

}

发现openFeign请求时，将变量放到请求头

/**
 * 基于openFeign的拦截器，处理需要向下游传递的信息.
 *
 * @author lind
 * @date 2023/1/29 11:44
 * @since 1.0.0
 */
@Configuration
public class FeignTraceIdInterceptor implements RequestInterceptor {

	@Override
	public void apply(RequestTemplate template) {

		if (NextHttpHeader.get() != null) {
			NextHttpHeader.get().forEach(o -> {
				template.header(o, NextHttpHeader.get(o));
			});
		}
	}

}

spring中的口子太多，太灵活，需要不断的去找那个最优雅，最正确的方法