添加@HystrixCommand导致ThreadLocal失效或null

[dengly]

在项目里使用了@HystrixCommand会导致ThreadLocal 为null。而我们使用的是THREAD隔离策略。网上搜索也知道了原因，可以参考这篇博文。

但是最终他的处理办法不推荐，在调试和看spring-security-core的 org.springframework.cloud.netflix.hystrix.security.SecurityContextConcurrencyStrategy和org.springframework.security.concurrent.DelegatingSecurityContextCallable给了我们解决办法。

添加以下类即可解决问题

@Configuration
public class ApiHystrixConfig {

    @Autowired(required = false)
    private HystrixConcurrencyStrategy existingConcurrencyStrategy;


    @PostConstruct
    public void init() {
        // Keeps references of existing Hystrix plugins.   保留现有Hystrix插件。
        HystrixEventNotifier eventNotifier = HystrixPlugins.getInstance()
                .getEventNotifier();
        HystrixMetricsPublisher metricsPublisher = HystrixPlugins.getInstance()
                .getMetricsPublisher();
        HystrixPropertiesStrategy propertiesStrategy = HystrixPlugins.getInstance()
                .getPropertiesStrategy();
        HystrixCommandExecutionHook commandExecutionHook = HystrixPlugins.getInstance()
                .getCommandExecutionHook();

        HystrixPlugins.reset();

        // Registers existing plugins excepts the Concurrent Strategy plugin. 注册除Concurrent Strategy插件之外的现有插件。
        HystrixPlugins.getInstance().registerConcurrencyStrategy(
                new ApiContextConcurrencyStrategy(existingConcurrencyStrategy));
        HystrixPlugins.getInstance().registerEventNotifier(eventNotifier);
        HystrixPlugins.getInstance().registerMetricsPublisher(metricsPublisher);
        HystrixPlugins.getInstance().registerPropertiesStrategy(propertiesStrategy);
        HystrixPlugins.getInstance().registerCommandExecutionHook(commandExecutionHook);
    }

    class ApiContextConcurrencyStrategy extends HystrixConcurrencyStrategy {
        private HystrixConcurrencyStrategy existingConcurrencyStrategy;

        public ApiContextConcurrencyStrategy(HystrixConcurrencyStrategy existingConcurrencyStrategy) {
            this.existingConcurrencyStrategy = existingConcurrencyStrategy;
        }

        @Override
        public BlockingQueue<Runnable> getBlockingQueue(int maxQueueSize) {
            return existingConcurrencyStrategy != null
                    ? existingConcurrencyStrategy.getBlockingQueue(maxQueueSize)
                    : super.getBlockingQueue(maxQueueSize);
        }

        @Override
        public <T> HystrixRequestVariable<T> getRequestVariable(HystrixRequestVariableLifecycle<T> rv) {
            return existingConcurrencyStrategy != null
                    ? existingConcurrencyStrategy.getRequestVariable(rv)
                    : super.getRequestVariable(rv);
        }

        @Override
        public ThreadPoolExecutor getThreadPool(HystrixThreadPoolKey threadPoolKey,
                                                HystrixProperty<Integer> corePoolSize,
                                                HystrixProperty<Integer> maximumPoolSize,
                                                HystrixProperty<Integer> keepAliveTime, TimeUnit unit,
                                                BlockingQueue<Runnable> workQueue) {
            return existingConcurrencyStrategy != null
                    ? existingConcurrencyStrategy.getThreadPool(threadPoolKey, corePoolSize,
                    maximumPoolSize, keepAliveTime, unit, workQueue)
                    : super.getThreadPool(threadPoolKey, corePoolSize, maximumPoolSize,
                    keepAliveTime, unit, workQueue);
        }

        @Override
        public <T> Callable<T> wrapCallable(Callable<T> callable) {
            return existingConcurrencyStrategy != null
                    ? existingConcurrencyStrategy
                    .wrapCallable(new ApiContextCallable<T>(callable))
                    : super.wrapCallable(new ApiContextCallable<T>(callable));
        }
    }

    class ApiContextCallable<V> implements Callable<V> {
        private final Callable<V> delegate;
        private final Object delegateObject;
        private Object originalObject;

        public ApiContextCallable(Callable<V> delegate, Object delegateObject) {
            Assert.notNull(delegate, "delegate cannot be null");
            this.delegate = delegate;
            this.delegateObject = delegateObject;
        }

        public ApiContextCallable(Callable<V> delegate) {
            this(delegate, TokenContext.get());
        }

        public V call() throws Exception {
            try {
                // 重点在这里 TokenContext 是我自己的上下文
                // TokenContext.get() 和 TokenContext.set() 都是对自己的ThreadLocal操作
                this.originalObject = TokenContext.get();
                TokenContext.set(this.delegateObject);
                V reV = this.delegate.call();
                return reV;
            } finally {
                TokenContext.set(this.originalObject);
                this.originalObject = null;
            }

        }

        public String toString() {
            return this.delegate.toString();
        }
    }
}

[dengly]

另使用了@HystrixCommand后，会涉及到并发问题，需要根据具体情况设置以下配置

hystrix:
  threadpool:
    default:
      coreSize: 100 ##并发执行的最大线程数，默认10
      maxQueueSize: 200 ##BlockingQueue的最大队列数
      queueSizeRejectionThreshold: 200 ##即使maxQueueSize没有达到，达到queueSizeRejectionThreshold该值后，请求也会被拒绝

[jinkunaier]

你这种做法当与spring security一起使用的时候不会覆盖org.springframework.cloud.netflix.hystrix.security.SecurityContextConcurrencyStrategy里面的配置吗？