diff --git a/lib/client/connection_mgr.js b/lib/client/connection_mgr.js
index 68e136e..286fe12 100644
--- a/lib/client/connection_mgr.js
+++ b/lib/client/connection_mgr.js
@@ -46,13 +46,25 @@ class ConnectionManager extends Base {
    * @return {Connection} 连接对象
    */
   get(address) {
-    const conn = this._connections.get(address.host);
+    const conn = this.doGetConn(address);
     if (conn && conn.isConnected) {
       return conn;
     }
     return null;
   }
 
+  doGetConn(address) {
+    return this._connections.get(address.host);
+  }
+
+  doSetConn(address, conn) {
+    return this._connections.set(address.host, conn);
+  }
+
+  doDeleteConn(address) {
+    this._connections.delete(address.host);
+  }
+
   /**
    * 若不存在，则创建新的连接
    *
@@ -63,14 +75,14 @@ class ConnectionManager extends Base {
    */
   async createAndGet(address, options, connectionClass) {
     connectionClass = connectionClass || this.options.connectionClass;
-    let conn = this._connections.get(address.host);
+    let conn = this.doGetConn(address);
     if (!conn) {
       conn = new connectionClass(Object.assign({
         address,
         logger: this.logger,
       }, options));
-      this._connections.set(address.host, conn);
-      conn.once('close', () => { this._connections.delete(address.host); });
+      this.doSetConn(address, conn);
+      conn.once('close', () => { this.doDeleteConn(address); });
       conn.once('error', err => { this.emit('error', err); });
     }
     if (!conn.isConnected) {
@@ -84,7 +96,7 @@ class ConnectionManager extends Base {
         }
       } catch (err) {
         this.logger.warn('[ConnectionManager] create connection: ' + address.href + ' failed, caused by ' + err.message);
-        this._connections.delete(address.host);
+        this.doDeleteConn(address);
         return null;
       }
     }