diff --git a/hugegraph-api/src/main/java/com/baidu/hugegraph/api/metrics/MetricsAPI.java b/hugegraph-api/src/main/java/com/baidu/hugegraph/api/metrics/MetricsAPI.java
index 2c94c7b6dd..35519cc45e 100644
--- a/hugegraph-api/src/main/java/com/baidu/hugegraph/api/metrics/MetricsAPI.java
+++ b/hugegraph-api/src/main/java/com/baidu/hugegraph/api/metrics/MetricsAPI.java
@@ -76,7 +76,7 @@ public String system() {
     @Timed
     @Path("backend")
     @Produces(APPLICATION_JSON_WITH_CHARSET)
-//    @RolesAllowed({"admin", "$owner= $action=metrics_read"})
+//  @RolesAllowed({"admin", "$owner= $action=metrics_read"})
     public String backend(@Context GraphManager manager) {
         Map<String, Map<String, Object>> results = InsertionOrderUtil.newMap();
         for (String graph : manager.graphs()) {
diff --git a/hugegraph-api/src/main/java/com/baidu/hugegraph/config/ServerOptions.java b/hugegraph-api/src/main/java/com/baidu/hugegraph/config/ServerOptions.java
index 0ba34e8f5a..a384e24d7c 100644
--- a/hugegraph-api/src/main/java/com/baidu/hugegraph/config/ServerOptions.java
+++ b/hugegraph-api/src/main/java/com/baidu/hugegraph/config/ServerOptions.java
@@ -227,8 +227,8 @@ public static synchronized ServerOptions instance() {
                     "auth.remote_url",
                     "If the address is empty, it provide auth service, " +
                     "otherwise it is auth client and also provide auth service " +
-                    "through rpc forwarding. The remote url can set multiple " +
-                    "addresses, which are linked by ','.",
+                    "through rpc forwarding. The remote url can be set to " +
+                    "multiple addresses, which are linked by ','.",
                     null,
                     ""
             );
@@ -280,7 +280,7 @@ public static synchronized ServerOptions instance() {
             new ConfigOption<>(
                     "rpc.client_load_balancer",
                     "The rpc client uses a load-balancing algorithm to " +
-                    "configure the addresses of multiple rpc servers. Default " +
+                    "access multiple rpc servers in one cluster. Default " +
                     "value is 'consistentHash', means forwording by request " +
                     "parameters.",
                     allowValues("random", "localPref", "roundRobin",
diff --git a/hugegraph-api/src/main/java/com/baidu/hugegraph/core/GraphManager.java b/hugegraph-api/src/main/java/com/baidu/hugegraph/core/GraphManager.java
index 8f3bf75d50..a94f0a788e 100644
--- a/hugegraph-api/src/main/java/com/baidu/hugegraph/core/GraphManager.java
+++ b/hugegraph-api/src/main/java/com/baidu/hugegraph/core/GraphManager.java
@@ -174,7 +174,9 @@ private RpcServerProvider startRpcServer(HugeConfig conf) {
     }
 
     private void destoryRpcServer() {
-        this.rpcServerProvider.destroy();
+        if (this.rpcServerProvider != null) {
+            this.rpcServerProvider.destroy();
+        }
     }
 
     private HugeAuthenticator authenticator() {
diff --git a/hugegraph-api/src/main/java/com/baidu/hugegraph/rpc/SofaRpcServer.java b/hugegraph-api/src/main/java/com/baidu/hugegraph/rpc/SofaRpcServer.java
index 56ec856b63..0496ff8a5d 100644
--- a/hugegraph-api/src/main/java/com/baidu/hugegraph/rpc/SofaRpcServer.java
+++ b/hugegraph-api/src/main/java/com/baidu/hugegraph/rpc/SofaRpcServer.java
@@ -58,8 +58,8 @@ public SofaRpcServer(HugeConfig conf, RpcProviderConfig providerConfig) {
 
     public void exportAll() {
         if (MapUtils.isEmpty(this.providerConfigs)) {
-            throw new RpcException("The server provider config map can't be " +
-                                   "empty");
+            throw new RpcException(
+                      "The server provider config map can't be empty");
         }
         for (ProviderConfig providerConfig : this.providerConfigs.values()) {
             providerConfig.setServer(this.serverConfig);