详解feign调用session丢失解决方案

@Configuration 
@EnableFeignClients(basePackages = "com.xxx.xxx.client") 
public class FeignClientsConfigurationCustom implements RequestInterceptor { 
 
 @Override 
 public void apply(RequestTemplate template) { 
 
  RequestAttributes requestAttributes = RequestContextHolder.getRequestAttributes(); 
  if (requestAttributes == null) { 
   return; 
  } 
 
  HttpServletRequest request = ((ServletRequestAttributes) requestAttributes).getRequest(); 
  Enumeration headerNames = request.getHeaderNames(); 
  if (headerNames != null) { 
   while (headerNames.hasMoreElements()) { 
    String name = headerNames.nextElement(); 
    Enumeration values = request.getHeaders(name); 
    while (values.hasMoreElements()) { 
     String value = values.nextElement(); 
     template.header(name, value); 
    } 
   } 
  } 
 
 } 
 
} 

RequestAttributes requestAttributes = RequestContextHolder.getRequestAttributes();

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

/**
 * Abstract class for defining different behavior or implementations for concurrency related aspects of the system with default implementations.
 * 

 * For example, every {@link Callable} executed by {@link HystrixCommand} will call {@link #wrapCallable(Callable)} to give a chance for custom implementations to decorate the {@link Callable} with
 * additional behavior.
 * 

 * When you implement a concrete {@link HystrixConcurrencyStrategy}, you should make the strategy idempotent w.r.t ThreadLocals.
 * Since the usage of threads by Hystrix is internal, Hystrix does not attempt to apply the strategy in an idempotent way.
 * Instead, you should write your strategy to work idempotently. See https://github.com/Netflix/Hystrix/issues/351 for a more detailed discussion.
 * 

 * See {@link HystrixPlugins} or the Hystrix GitHub Wiki for information on configuring plugins: https://github.com/Netflix/Hystrix/wiki/Plugins.
 */
public abstract class HystrixConcurrencyStrategy 

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.getInstance().registerConcurrencyStrategy(this); 
   HystrixPlugins.getInstance().registerCommandExecutionHook(commandExecutionHook); 
   HystrixPlugins.getInstance().registerEventNotifier(eventNotifier); 
   HystrixPlugins.getInstance().registerMetricsPublisher(metricsPublisher); 
   HystrixPlugins.getInstance().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  Callable wrapCallable(Callable callable) { 
  RequestAttributes requestAttributes = RequestContextHolder.getRequestAttributes(); 
  return new WrappedCallable<>(callable, requestAttributes); 
 } 
 
 @Override 
 public ThreadPoolExecutor getThreadPool(HystrixThreadPoolKey threadPoolKey, 
   HystrixProperty corePoolSize, HystrixProperty maximumPoolSize, 
   HystrixProperty keepAliveTime, TimeUnit unit, BlockingQueue 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 getBlockingQueue(int maxQueueSize) { 
  return this.delegate.getBlockingQueue(maxQueueSize); 
 } 
 
 @Override 
 public  HystrixRequestVariable getRequestVariable(HystrixRequestVariableLifecycle rv) { 
  return this.delegate.getRequestVariable(rv); 
 } 
 
 static class WrappedCallable implements Callable { 
  private final Callable target; 
  private final RequestAttributes requestAttributes; 
 
  public WrappedCallable(Callable 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(); 
   } 
  } 
 } 
} 

 @Bean
 public FeignHystrixConcurrencyStrategy feignHystrixConcurrencyStrategy() {
  return new FeignHystrixConcurrencyStrategy();
 }