No provider available for the service com.alibaba.dubbo.monitor.MonitorService
dubbo消费端一直报如下错误：
该错误对功能没有任何影响，但反复的报错也是必须要解决的。
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2016-10-18 08:34:00.725 [DubboMonitorSendTimer-thread-1] ERROR c.a.dubbo.monitor.dubbo.DubboMonitor - [DUBBO] Unexpected error occur at send statistic, cause: Failed to invoke the method collect in the service com.alibaba.dubbo.monitor.MonitorService. No provider available for the service com.alibaba.dubbo.monitor.MonitorService from registry 192.168.0.45:2181 on the consumer 192.168.0.180 using the dubbo version 2.8.4. Please check if the providers have been started and registered., dubbo version: 2.8.4, current host: 192.168.0.180
com.alibaba.dubbo.rpc.RpcException: Failed to invoke the method collect in the service com.alibaba.dubbo.monitor.MonitorService. No provider available for the service com.alibaba.dubbo.monitor.MonitorService from registry 192.168.0.45:2181 on the consumer 192.168.0.180 using the dubbo version 2.8.4. Please check if the providers have been started and registered.
at com.alibaba.dubbo.rpc.cluster.support.AbstractClusterInvoker.checkInvokers(AbstractClusterInvoker.java:246) ~[dubbo-2.8.4.jar:2.8.4]
at com.alibaba.dubbo.rpc.cluster.support.FailoverClusterInvoker.doInvoke(FailoverClusterInvoker.java:55) ~[dubbo-2.8.4.jar:2.8.4]
at com.alibaba.dubbo.rpc.cluster.support.AbstractClusterInvoker.invoke(AbstractClusterInvoker.java:227) ~[dubbo-2.8.4.jar:2.8.4]
at com.alibaba.dubbo.rpc.cluster.support.wrapper.MockClusterInvoker.invoke(MockClusterInvoker.java:72) ~[dubbo-2.8.4.jar:2.8.4]
at com.alibaba.dubbo.rpc.proxy.InvokerInvocationHandler.invoke(InvokerInvocationHandler.java:52) ~[dubbo-2.8.4.jar:2.8.4]
at com.alibaba.dubbo.common.bytecode.proxy23.collect(proxy23.java) ~[dubbo-2.8.4.jar:2.8.4]
at com.alibaba.dubbo.monitor.dubbo.DubboMonitor.send(DubboMonitor.java:113) ~[dubbo-2.8.4.jar:2.8.4]
at com.alibaba.dubbo.monitor.dubbo.DubboMonitor$1.run(DubboMonitor.java:70) ~[dubbo-2.8.4.jar:2.8.4]
at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:471) [na:1.7.0_10]
at java.util.concurrent.FutureTask$Sync.innerRunAndReset(FutureTask.java:351) [na:1.7.0_10]
at java.util.concurrent.FutureTask.runAndReset(FutureTask.java:178) [na:1.7.0_10]
at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$301(ScheduledThreadPoolExecutor.java:178) [na:1.7.0_10]
at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:293) [na:1.7.0_10]
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1110) [na:1.7.0_10]
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:603) [na:1.7.0_10]
at java.lang.Thread.run(Thread.java:722) [na:1.7.0_10]
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这是因为没有启动监控中心，却配了监控地址，把监控中心启动，或者把xml配置中的<dubbo:monitor protocol="registry">或properties配置中的dubbo.monitor.protocol=registry去掉。问题解决。