Never reset a connection with client error code

lib/MySQL_HostGroups_Manager.cpp

@@ -3114,10 +3114,15 @@ void MySQL_HostGroups_Manager::destroy_MyConn_from_pool(MySQL_Connection *c, boo
 	if (mysrvc->status==MYSQL_SERVER_STATUS_ONLINE && c->send_quit && queue.size() < __sync_fetch_and_add(&GloMTH->variables.connpoll_reset_queue_length,0)) {
 		if (c->async_state_machine==ASYNC_IDLE) {
 			// overall, the backend seems healthy and so it is the connection. Try to reset it
-			proxy_debug(PROXY_DEBUG_MYSQL_CONNPOOL, 7, "Trying to reset MySQL_Connection %p, server %s:%d\n", c, mysrvc->address, mysrvc->port);
-			to_del=false;
-			//c->userinfo->set(mysql_thread___monitor_username,mysql_thread___monitor_password,mysql_thread___default_schema,NULL);
-			queue.add(c);
+			int myerr=mysql_errno(c->mysql);
+			if (myerr >= 2000 && myerr < 3000) {
+				// client library error . We must not try to save the connection
+				proxy_debug(PROXY_DEBUG_MYSQL_CONNPOOL, 7, "Not trying to reset MySQL_Connection %p, server %s:%d . Error code %d\n", c, mysrvc->address, mysrvc->port, myerr);
+			} else {
+				proxy_debug(PROXY_DEBUG_MYSQL_CONNPOOL, 7, "Trying to reset MySQL_Connection %p, server %s:%d\n", c, mysrvc->address, mysrvc->port);
+				to_del=false;
+				queue.add(c);
+			}
 		} else {
 		// the connection seems health, but we are trying to destroy it
 		// probably because there is a long running query