[TODO]com.alibaba.dubbo.rpc.RpcException: Failed to invoke the method

异常信息如下：

2018-10-30 20:00:50.230 ERROR 
java.util.concurrent.ExecutionException: com.alibaba.dubbo.rpc.RpcException: Failed to invoke the method query in the service cn.fraudmetrix.skuld.api.client.intf.IListValueService. Tried 1 times of the providers [192.168.72.95:20880] (1/10) from the registry 192.168.47.83:2181 on the consumer 192.168.127.80 using the dubbo version 2.5.3. Last error is: null
        at java.util.concurrent.FutureTask.report(FutureTask.java:122) ~[na:1.8.0_60]
        at java.util.concurrent.FutureTask.get(FutureTask.java:192) ~[na:1.8.0_60]
        at cn.fraudmetrix.alliance.service.MobilPhoneRuleService.getMobilPhoneRuleObj(MobilPhoneRuleService.java:73) ~[alliance-biz-service-1.0.0.jar:na]
        at cn.fraudmetrix.alliance.service.impl.MobilPhoneInfoServiceImpl.lambda$getMobilPhoneRule$1(MobilPhoneInfoServiceImpl.java:143) [alliance-biz-service-1.0.0.jar:na]
        at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142) ~[na:1.8.0_60]
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617) ~[na:1.8.0_60]
        at java.lang.Thread.run(Thread.java:745) ~[na:1.8.0_60]
Caused by: com.alibaba.dubbo.rpc.RpcException: Failed to invoke the method query in the service cn.fraudmetrix.skuld.api.client.intf.IListValueService. Tried 1 times of the providers [192.168.72.95:20880] (1/10) from the registry 192.168.47.83:2181 on the consumer 192.168.127.80 using the dubbo version 2.5.3. Last error is: null
        at com.alibaba.dubbo.rpc.cluster.support.FailoverClusterInvoker.doInvoke(FailoverClusterInvoker.java:101) ~[dubbo-2.5.3.jar:2.5.3]
        at com.alibaba.dubbo.rpc.cluster.support.AbstractClusterInvoker.invoke(AbstractClusterInvoker.java:227) ~[dubbo-2.5.3.jar:2.5.3]
        at com.alibaba.dubbo.rpc.cluster.support.wrapper.MockClusterInvoker.invoke(MockClusterInvoker.java:72) ~[dubbo-2.5.3.jar:2.5.3]
        at com.alibaba.dubbo.rpc.proxy.InvokerInvocationHandler.invoke(InvokerInvocationHandler.java:52) ~[dubbo-2.5.3.jar:2.5.3]
        at com.alibaba.dubbo.common.bytecode.proxy1.query(proxy1.java) ~[na:2.5.3]
        at cn.fraudmetrix.alliance.service.processor.BadAttributeProcessor.execute(BadAttributeProcessor.java:55) ~[alliance-biz-service-1.0.0.jar:na]
        at cn.fraudmetrix.alliance.service.processor.BadAttributeProcessor.execute(BadAttributeProcessor.java:22) ~[alliance-biz-service-1.0.0.jar:na]
        at cn.fraudmetrix.alliance.service.processor.AbstractProcessor.process(AbstractProcessor.java:17) ~[alliance-biz-service-1.0.0.jar:na]
        at cn.fraudmetrix.alliance.service.processor.AbstractProcessor$$FastClassBySpringCGLIB$$a202aaec.invoke(<generated>) ~[alliance-biz-service-1.0.0.jar:na]
        at org.springframework.cglib.proxy.MethodProxy.invoke(MethodProxy.java:204) ~[spring-core-4.3.0.RELEASE.jar:4.3.0.RELEASE]
        at org.springframework.aop.framework.CglibAopProxy$CglibMethodInvocation.invokeJoinpoint(CglibAopProxy.java:720) ~[spring-aop-4.3.0.RELEASE.jar:4.3.0.RELEASE]
        at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:157) ~[spring-aop-4.3.0.RELEASE.jar:4.3.0.RELEASE]
        at org.springframework.aop.aspectj.MethodInvocationProceedingJoinPoint.proceed(MethodInvocationProceedingJoinPoint.java:85) ~[spring-aop-4.3.0.RELEASE.jar:4.3.0.RELEASE]
        at cn.fraudmetrix.alliance.service.aop.MetricsAop.execute(MetricsAop.java:27) ~[alliance-biz-service-1.0.0.jar:na]
        at sun.reflect.GeneratedMethodAccessor41.invoke(Unknown Source) ~[na:na]
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:1.8.0_60]
        at java.lang.reflect.Method.invoke(Method.java:497) ~[na:1.8.0_60]
        at org.springframework.aop.aspectj.AbstractAspectJAdvice.invokeAdviceMethodWithGivenArgs(AbstractAspectJAdvice.java:629) ~[spring-aop-4.3.0.RELEASE.jar:4.3.0.RELEASE]
        at org.springframework.aop.aspectj.AbstractAspectJAdvice.invokeAdviceMethod(AbstractAspectJAdvice.java:618) ~[spring-aop-4.3.0.RELEASE.jar:4.3.0.RELEASE]
        at org.springframework.aop.aspectj.AspectJAroundAdvice.invoke(AspectJAroundAdvice.java:70) ~[spring-aop-4.3.0.RELEASE.jar:4.3.0.RELEASE]
        at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179) ~[spring-aop-4.3.0.RELEASE.jar:4.3.0.RELEASE]
        at org.springframework.aop.interceptor.ExposeInvocationInterceptor.invoke(ExposeInvocationInterceptor.java:92) ~[spring-aop-4.3.0.RELEASE.jar:4.3.0.RELEASE]
        at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179) ~[spring-aop-4.3.0.RELEASE.jar:4.3.0.RELEASE]
        at org.springframework.aop.framework.CglibAopProxy$DynamicAdvisedInterceptor.intercept(CglibAopProxy.java:655) ~[spring-aop-4.3.0.RELEASE.jar:4.3.0.RELEASE]
        at cn.fraudmetrix.alliance.service.processor.BadAttributeProcessor$$EnhancerBySpringCGLIB$$2f8bd77e.process(<generated>) ~[alliance-biz-service-1.0.0.jar:na]
        at cn.fraudmetrix.alliance.service.MobilPhoneRuleService.lambda$getMobilPhoneRuleObj$5(MobilPhoneRuleService.java:54) ~[alliance-biz-service-1.0.0.jar:na]
        at java.util.concurrent.FutureTask.run(FutureTask.java:266) ~[na:1.8.0_60]
        ... 3 common frames omitted
java.lang.NullPointerException: null

注意以上类，翻开源码：

package com.alibaba.dubbo.rpc.cluster.support;
/**
 * 失败转移，当出现失败，重试其它服务器，通常用于读操作，但重试会带来更长延迟。
 *
 * <a href="http://en.wikipedia.org/wiki/Failover">Failover</a>
 *
 * @author william.liangf
 * @author chao.liuc
 */
public class FailoverClusterInvoker<T> extends AbstractClusterInvoker<T> {

    private static final Logger logger = LoggerFactory.getLogger(FailoverClusterInvoker.class);

    public FailoverClusterInvoker(Directory<T> directory) {
        super(directory);
    }

    @SuppressWarnings({ "unchecked", "rawtypes" })
    public Result doInvoke(Invocation invocation, final List<Invoker<T>> invokers, LoadBalance loadbalance) throws RpcException {
        List<Invoker<T>> copyinvokers = invokers;
        checkInvokers(copyinvokers, invocation);
        int len = getUrl().getMethodParameter(invocation.getMethodName(), Constants.RETRIES_KEY, Constants.DEFAULT_RETRIES) + 1;
        if (len <= 0) {
            len = 1;
        }
        // retry loop.
        RpcException le = null; // last exception.
        List<Invoker<T>> invoked = new ArrayList<Invoker<T>>(copyinvokers.size()); // invoked invokers.
        Set<String> providers = new HashSet<String>(len);
        for (int i = 0; i < len; i++) {
            //重试时，进行重新选择，避免重试时invoker列表已发生变化.
            //注意：如果列表发生了变化，那么invoked判断会失效，因为invoker示例已经改变
            if (i > 0) {
                checkWheatherDestoried();
                copyinvokers = list(invocation);
                //重新检查一下
                checkInvokers(copyinvokers, invocation);
            }
            Invoker<T> invoker = select(loadbalance, invocation, copyinvokers, invoked);
            invoked.add(invoker);
            RpcContext.getContext().setInvokers((List)invoked);
            try {
                Result result = invoker.invoke(invocation);
                if (le != null && logger.isWarnEnabled()) {
                    logger.warn("Although retry the method " + invocation.getMethodName()
                            + " in the service " + getInterface().getName()
                            + " was successful by the provider " + invoker.getUrl().getAddress()
                            + ", but there have been failed providers " + providers
                            + " (" + providers.size() + "/" + copyinvokers.size()
                            + ") from the registry " + directory.getUrl().getAddress()
                            + " on the consumer " + NetUtils.getLocalHost()
                            + " using the dubbo version " + Version.getVersion() + ". Last error is: "
                            + le.getMessage(), le);
                }
                return result;
            } catch (RpcException e) {
                if (e.isBiz()) { // biz exception.
                    throw e;
                }
                le = e;
            } catch (Throwable e) {
                le = new RpcException(e.getMessage(), e);
            } finally {
                providers.add(invoker.getUrl().getAddress());
            }
        }
        throw new RpcException(le != null ? le.getCode() : 0, "Failed to invoke the method "
                + invocation.getMethodName() + " in the service " + getInterface().getName()
                + ". Tried " + len + " times of the providers " + providers
                + " (" + providers.size() + "/" + copyinvokers.size()
                + ") from the registry " + directory.getUrl().getAddress()
                + " on the consumer " + NetUtils.getLocalHost() + " using the dubbo version "
                + Version.getVersion() + ". Last error is: "
                + (le != null ? le.getMessage() : ""), le != null && le.getCause() != null ? le.getCause() : le);
    }

}

跟踪异常栈，可以抛出异常在以下地方：

关注初始报错信息：

java.util.concurrent.ExecutionException: com.alibaba.dubbo.rpc.RpcException: 
Failed to invoke the method query in the service cn.fraudmetrix.skuld.api.client.intf.IListValueService. 
Tried 1 times of the providers [192.168.121.230:20880] (1/10) from the registry 192.168.47.83:2181 on the consumer 192.168.55.67 
using the dubbo version 2.5.3. Last error is: null

注意以上是null, 问题就在这里，网上找了一些资料，也没发现相关的原因，只能本地翻看源码论证可能性：

可能性1： 请求超时：

异常信息：

Failed to invoke the method query in the service cn.fraudmetrix.skuld.api.client.intf.IListValueService. 
Tried 3 times of the providers [10.57.240.10:20880] (1/1) from the registry 192.168.6.55:2181 on the consumer 10.57.240.10 
using the dubbo version 2.5.3. Last error is: 
Invoke remote method timeout. method: query, provider: dubbo://10.57.240.10:20880/....

后面有具体的原因，timeout，一目了然。

可能性2：服务提供者未启动：

异常信息：

om.alibaba.dubbo.rpc.RpcException: Forbid consumer 10.57.240.10 access service cn.fraudmetrix.skuld.api.client.intf.IListValueService from registry 192.168.6.55:2181 use dubbo version 2.5.3, Please check registry access list (whitelist/blacklist).
    at com.alibaba.dubbo.registry.integration.RegistryDirectory.doList(RegistryDirectory.java:579)
    at com.alibaba.dubbo.rpc.cluster.directory.AbstractDirectory.list(AbstractDirectory.java:73)
    at com.alibaba.dubbo.rpc.cluster.support.AbstractClusterInvoker.list(AbstractClusterInvoker.java:260)
    at com.alibaba.dubbo.rpc.cluster.support.AbstractClusterInvoker.invoke(AbstractClusterInvoker.java:219)
    at com.alibaba.dubbo.rpc.cluster.support.wrapper.MockClusterInvoker.invoke(MockClusterInvoker.java:72)
    at com.alibaba.dubbo.rpc.proxy.InvokerInvocationHandler.invoke(InvokerInvocationHandler.java:52)
    at com.alibaba.dubbo.common.bytecode.proxy0.query(proxy0.java)
    at cn.fraudmetrix.skuld.dubbotest.ValueQueryTest.runTest(ValueQueryTest.java:70)
    at cn.fraudmetrix.skuld.dubbotest.App.main(App.java:15)

在AbstractClusterInvoker中有以下代码：

List<Invoker<T>> invokers = doList(invocation);

直接异常了。

可能性3：服务提供者启动，跳过验证后宕机：

异常信息：

Failed to invoke the method query in the service cn.fraudmetrix.skuld.api.client.intf.IListValueService. 
Tried 3 times of the providers [10.57.240.10:20880] (1/1) from the registry 192.168.6.55:2181 on the consumer 10.57.240.10 
using the dubbo version 2.5.3. Last error is: 
Failed to invoke remote method: query, provider: dubbo://10.57.240.10:20880/.....

后面也有相关的原因。

现在报个null还不好找原因啊。