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。
------------------------------------------------------------------------------------------
2016-10-18 08:34:00.725 [DubboMonitorSendTimer-thread-1] ERROR - [DUBBO] Unexpected error occur at send statistic, cause: Failed to invoke the method collect in the service . No provider available for the service 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
: Failed to invoke the method collect in the service . No provider available for the service 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 (:246) ~[dubbo-2.8.:2.8.4]
at (:55) ~[dubbo-2.8.:2.8.4]
at (:227) ~[dubbo-2.8.:2.8.4]
at (:72) ~[dubbo-2.8.:2.8.4]
at (:52) ~[dubbo-2.8.:2.8.4]
at .() ~[dubbo-2.8.:2.8.4]
at (:113) ~[dubbo-2.8.:2.8.4]
at $(:70) ~[dubbo-2.8.:2.8.4]
at $(:471) [na:1.7.0_10]
at $(:351) [na:1.7.0_10]
at (:178) [na:1.7.0_10]
at $$301(:178) [na:1.7.0_10]
at $(:293) [na:1.7.0_10]
at (:1110) [na:1.7.0_10]
at $(:603) [na:1.7.0_10]
at (:722) [na:1.7.0_10]
------------------------------------------------------------------------------------------
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=registry去掉。问题解决。