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+
+## NameNode客户端协议详解
+
+协议的定义主要在类NamenodeProtocols中。如下：
+
+```java
+public interface NamenodeProtocols
+  extends ClientProtocol,
+          DatanodeProtocol,
+          DatanodeLifelineProtocol,
+          NamenodeProtocol,
+          RefreshAuthorizationPolicyProtocol,
+          ReconfigurationProtocol,
+          RefreshUserMappingsProtocol,
+          RefreshCallQueueProtocol,
+          GenericRefreshProtocol,
+          GetUserMappingsProtocol,
+          HAServiceProtocol {
+}
+```
+其中NameNode相关的大多数在NamenodeProtocol当中。
+
+### NamenodeProtocol 详解
+
+