[ISSUE #11718] Fix ErrorCode have the same code

api/src/main/java/com/alibaba/nacos/api/model/v2/ErrorCode.java

@@ -178,7 +178,7 @@ public enum ErrorCode {
     /**
      *  node down failure.
      */
-    NODE_DOWN_FAILURE(23001, "node down failure"),
+    NODE_DOWN_FAILURE(23002, "node down failure"),
 
     /**
      *  server error.

api/src/test/java/com/alibaba/nacos/api/model/v2/ErrorCodeTest.java

@@ -0,0 +1,24 @@
+package com.alibaba.nacos.api.model.v2;
+
+import static org.junit.Assert.assertEquals;
+
+import java.util.HashSet;
+import java.util.Set;
+
+import org.junit.Test;
+
+public class ErrorCodeTest {
+	@Test
+    public void testCodeNotSame() {
+        Class<ErrorCode> errorCodeClass = ErrorCode.class;
+
+        ErrorCode[] errorCodes = errorCodeClass.getEnumConstants();
+        Set<Integer> codeSet = new HashSet<Integer>(errorCodes.length);
+
+        for(ErrorCode errorCode : errorCodes) {
+        	codeSet.add(errorCode.getCode());
+        }
+
+        assertEquals(errorCodes.length, codeSet.size());
+    }
+}