Failed to invoke the method subscribe in the service com.alibaba.dubbo.registry.RegistryService

1 异常信息

今天在写 dubbo 文章的时候遇到一个问题，倒是折腾了几分钟，百思不得其解，最后终于发现了。异常信息如下：

com.alibaba.dubbo.rpc.RpcException: Failed to invoke the method subscribe in the service com.alibaba.dubbo.registry.RegistryService. Tried 3 times of the providers [localhost:2181, localhost:2182, localhost:2183] (3/3) from the registry localhost:2182 on the consumer 192.168.234.1 using the dubbo version 2.6.6. Last error is: Invoke remote method timeout. method: subscribe, provider: dubbo://localhost:2181/com.alibaba.dubbo.registry.RegistryService?application=provider&backup=localhost:2183,localhost:2181&callbacks=10000&check=false&connect.timeout=10000&dubbo=2.0.2&interface=com.alibaba.dubbo.registry.RegistryService&lazy=true&methods=lookup,subscribe,unsubscribe,unregister,register&owner=sihai&pid=2872&qos.accept.foreign.ip=false&qos.enable=true&qos.port=55555&reconnect=false&remote.timestamp=1564280535444&sticky=true&subscribe.1.callback=true&timeout=10000&timestamp=1564280535444&unsubscribe.1.callback=false, cause: Waiting server-side response timeout by scan timer. start time: 2019-07-28 10:22:38.380, end time: 2019-07-28 10:22:48.401, client elapsed: 9 ms, server elapsed: 10011 ms, timeout: 10000 ms, request: Request [id=2, version=2.0.2, twoway=true, event=false, broken=false, data=RpcInvocation [methodName=subscribe, parameterTypes=[class com.alibaba.dubbo.common.URL, interface com.alibaba.dubbo.registry.NotifyListener], arguments=[consumer://192.168.234.1/com.alibaba.dubbo.registry.RegistryService?application=provider&backup=localhost:2183,localhost:2181&callbacks=10000&connect.timeout=10000&dubbo=2.0.2&interface=com.alibaba.dubbo.registry.RegistryService&lazy=true&methods=lookup,subscribe,unsubscribe,unregister,register&owner=sihai&pid=2872&qos.accept.foreign.ip=false&qos.enable=true&qos.port=55555&reconnect=false&sticky=true&subscribe.1.callback=true&timeout=10000&timestamp=1564280535444&unsubscribe.1.callback=false, com.alibaba.dubbo.registry.integration.RegistryDirectory@353352b6], attachments={path=com.alibaba.dubbo.registry.RegistryService, sys_callback_arg-1=892555958, interface=com.alibaba.dubbo.registry.RegistryService, version=0.0.0, timeout=10000}]], channel: 192.168.234.1:0 -> localhost/127.0.0.1:2181
	at com.alibaba.dubbo.rpc.cluster.support.FailoverClusterInvoker.doInvoke(FailoverClusterInvoker.java:102)
	at com.alibaba.dubbo.rpc.cluster.support.AbstractClusterInvoker.invoke(AbstractClusterInvoker.java:244)
	at com.alibaba.dubbo.rpc.cluster.support.wrapper.MockClusterInvoker.invoke(MockClusterInvoker.java:75)
	at com.alibaba.dubbo.rpc.proxy.InvokerInvocationHandler.invoke(InvokerInvocationHandler.java:52)
	at com.alibaba.dubbo.common.bytecode.proxy0.subscribe(proxy0.java)
	at com.alibaba.dubbo.registry.dubbo.DubboRegistry.doSubscribe(DubboRegistry.java:151)
	at com.alibaba.dubbo.registry.support.FailbackRegistry.subscribe(FailbackRegistry.java:196)

其中，可以发现最重要异常信息就是：

com.alibaba.dubbo.rpc.RpcException: Failed to invoke the method subscribe in the service com.alibaba.dubbo.registry.RegistryService

如果你了解 dubbo 的架构的话，其实你很快就能发现，这就是注册中心的问题。后来排查发现，确实是注册中心出了问题。

2 解决问题

知道是注册中心出现了问题，刚刚开始以为是我设置了只订阅的模式，但是，检查配置发现，并不是这种模式出现了问题。

后来，再仔细看了一下之前的配置发现，是我没有指明注册中心是哪个？（以前用的是zookeeper）。

所以，到这里就很简单了，在下面的代码中指明注册中心即可。

<dubbo:registry timeout="10000" address="localhost:2182,localhost:2183,localhost:2181"></dubbo:registry>

改为

<dubbo:registry protocol="zookeeper" timeout="10000" address="localhost:2182,localhost:2183,localhost:2181"></dubbo:registry>

这样问题就解决了。