springCloud微服务系列——OAuth2+JWT模式下的feign+hystrix处理

￡神魔★判官ぃ 2022-05-21 04:59 164阅读 0赞

之前的文章说了一下JWT模式下feign调用其他服务的时候，怎么通过一个方法使得http请求头的信息传递到被调服务中。当然也可以用@RequestHeader注解，但是这样并不是太好，因为我们希望有一个全局的处理。这些问题可以参看之前的文章。

[《springCloud微服务系列——OAuth2+JWT模式下的swagger+feign处理》][springCloud_OAuth2_JWT_swagger_feign]

这篇文章将总结的问题是，同样基于feign模式，但是开启了hystrix，那么之前的方式传递http请求头就已经失效了。这里将介绍如何解决这个问题。

一、hystrix源码剖析-追根溯源

为什么开启了hystrix就不能获取到http请求头信息了呢，做了一定的源码分析。最后总结为下图：

![70][]

该图展示了开启hystrix后一些比较重要的执行点，hystrix通过命令模式，通过hystrixCommond.execute()进行调用服务。关键是通过future模式和rxJava开启了一个新线程处理请求，最后调用feign的ribbon负载均衡。我们知道，spring mvc为了我们在controller层以外也能获得到http请求，使用了基于localThread的requestContextHolder，在这里面我们可以拿到所有的http请求信息。但是这里新启了一个线程后，当然在之前实现的拦截器中，无法通过requestContextHolder访问到以前的http请求信息了。

这里回顾一下上篇文章中的拦截器，我们看一下获取http请求的方法

private HttpServletRequest getHttpServletRequest() {
            try {
                return ((ServletRequestAttributes) RequestContextHolder.getRequestAttributes()).getRequest();
            } catch (Exception e) {
                return null;
            }
        }

再来总结一下整个执行过程hystrixCommond.execute()->return queue().get()\[新线程\]->hystixCommond.run()->feign.ribbon.LoadBalancerFeignClient执行http请求->我们实现的拦截器->getHttpServletRequest->((ServletRequestAttributes)) RequestContextHolder.getRequestAttributes()).getRequest()

整个原因一目了然

二、解决方案

怎么解决问题呢？其实spring cloud自身也有很多地方需要这种跨线程的操作，所以它自己有一个类名为HystrixConcurrencyStrategy。我们可以看到它为spring security提供了一个实现SecurityContextConcurrencyStrategy，为sleuth提供了一个实现SleuthHystrixConcurrencyStrategy。我们要做的就是模仿这两个实现类，实现一个我们自己的HystrixConcurrencyStrategy类。这里就直接上代码了

@Component
    public class RequestAttributeHystrixConcurrencyStrategy extends HystrixConcurrencyStrategy {
    
    	private static final Logger logger = LoggerFactory.getLogger(RequestAttributeHystrixConcurrencyStrategy.class);
    	private HystrixConcurrencyStrategy delegate;
    	public RequestAttributeHystrixConcurrencyStrategy() {
    		try {
    			this.delegate = HystrixPlugins.getInstance().getConcurrencyStrategy();
    			if (this.delegate instanceof RequestAttributeHystrixConcurrencyStrategy) {
    				// 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) {
    			logger.error("Failed to register Sleuth Hystrix Concurrency Strategy", e);
    		}
    	}
    	private void logCurrentStateOfHystrixPlugins(HystrixEventNotifier eventNotifier,
    			HystrixMetricsPublisher metricsPublisher,
    			HystrixPropertiesStrategy propertiesStrategy) {
    		if (logger.isDebugEnabled()) {
    			logger.debug("Current Hystrix plugins configuration is ["
    					+ "concurrencyStrategy [" + this.delegate + "]," + "eventNotifier ["
    					+ eventNotifier + "]," + "metricPublisher [" + metricsPublisher + "],"
    					+ "propertiesStrategy [" + propertiesStrategy + "]," + "]");
    			logger.debug("Registering Sleuth Hystrix Concurrency Strategy.");
    		}
    	}
    	@Override
    	public <T> Callable<T> wrapCallable(Callable<T> callable) {
    		if (callable instanceof HttpRequestWrappedCallable) {
    			return callable;
    		}
    		Callable<T> wrappedCallable = this.delegate != null
    				? this.delegate.wrapCallable(callable) : callable;
    		if (wrappedCallable instanceof HttpRequestWrappedCallable) {
    			return wrappedCallable;
    		}
    		RequestAttributes requestAttributes = RequestContextHolder.getRequestAttributes();
    		return new HttpRequestWrappedCallable<>(callable, requestAttributes);
    	}
    	@Override
    	public ThreadPoolExecutor getThreadPool(HystrixThreadPoolKey threadPoolKey,
    			HystrixProperty<Integer> corePoolSize,
    			HystrixProperty<Integer> maximumPoolSize,
    			HystrixProperty<Integer> keepAliveTime, TimeUnit unit,
    			BlockingQueue<Runnable> 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<Runnable> getBlockingQueue(int maxQueueSize) {
    		return this.delegate.getBlockingQueue(maxQueueSize);
    	}
    	@Override
    	public <T> HystrixRequestVariable<T> getRequestVariable(
    			HystrixRequestVariableLifecycle<T> rv) {
    		return this.delegate.getRequestVariable(rv);
    	}
    	static class HttpRequestWrappedCallable<T> implements Callable<T> {
    		private final Callable<T> target;
    		private final RequestAttributes requestAttributes;
    		public HttpRequestWrappedCallable(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();
    			}
    		}
    	}
    	
    }

[springCloud_OAuth2_JWT_swagger_feign]: https://blog.csdn.net/guduyishuai/article/details/80384076
[70]: /images/20220521/b1e6b8cf55e145989ef382b322324976.png