我們都知道，在hystrix默認情況下，采用線程池的熔斷方式，每個openfeign都有自己的線程，而這使得它無法獲取主線程上的變量；現在有個現實的問題就是，當前端登錄后，把token經過gateway傳到服務A，服務A再調用服務B時，B是無法收到請求頭里的token信息的；一種不太好的解決方案就是使用信號量的方式。

使用ThreadLocal存儲變量

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();
	}


}

繼承HystrixConcurrencyStrategy抽象類，實現自己的賦值邏輯

public class RequestContextHystrixConcurrencyStrategy extends HystrixConcurrencyStrategy {

	public <T> Callable<T> wrapCallable(Callable<T> callable) {
		// 先包裝一下要執行的任務，在這里把ThreadLocal的值取出來
		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();
		}

	}

}

注冊

@Configuration
@Slf4j
public class HystrixCircuitBreakerConfiguration {

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

}

發現openFeign請求時，將變量放到請求頭

/**
 * 基于openFeign的攔截器，處理需要向下游傳遞的信息.
 *
 * @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，太靈活，需要不斷的去找那個最優雅，最正確的方法