text: /*
   * Copyright (c) 2020, Oracle and/or its affiliates.
   *
   * This program is free software; you can redistribute it and/or modify
   * it under the terms of the GNU General Public License, version 2.0, as
   * published by the Free Software Foundation.
   *
   * This program is also distributed with certain software (including
   * but not limited to OpenSSL) that is licensed under separate terms,
   * as designated in a particular file or component or in included license
   * documentation.  The authors of MySQL hereby grant you an
   * additional permission to link the program and your derivative works
   * with the separately licensed software that they have included with
   * MySQL.
   *
   * Without limiting anything contained in the foregoing, this file,
   * which is part of MySQL Connector/Node.js, is also subject to the
   * Universal FOSS Exception, version 1.0, a copy of which can be found at
   * http://oss.oracle.com/licenses/universal-foss-exception.
   *
   * This program is distributed in the hope that it will be useful, but
   * WITHOUT ANY WARRANTY; without even the implied warranty of
   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
   * See the GNU General Public License, version 2.0, for more details.
   *
   * You should have received a copy of the GNU General Public License
   * along with this program; if not, write to the Free Software Foundation, Inc.,
   * 51 Franklin St, Fifth Floor, Boston, MA 02110-1301  USA
   */
  
  'use strict';
  
  const mysqlx = require('../../');
  const BACKOFF_INCREASE = 1000; // fixed increased in backoff
  
  /**
   * Delay pinging hosts for a given period of time.
   * @private
   * @param {object[]} [hosts] - the list of hosts to ping
   * @param {number} [waitFor] - time to wait
   * @returns {Promise}
   */
  function pingAfter (hosts, waitFor) {
      return new Promise((resolve, reject) => {
          setTimeout(() => {
              return ping(hosts, waitFor + BACKOFF_INCREASE).then(resolve).catch(reject);
          }, waitFor);
      });
  };
  
  /**
   * Ping a list of hosts until they are available.
   * @private
   * @param {object[]} [hosts] - the list of hosts to ping
   * @param {number} [backoff] - initial backoff
   * @returns {Promise}
   */
  function ping (hosts, backoff) {
      hosts = hosts || [];
      backoff = backoff || 0;
  
      const pipeline = hosts.map(host => mysqlx.getSession({ host: host.trim() }));
  
      return Promise.all(pipeline)
          .then(sessions => {
              return sessions.map(session => session.close());
          })
          .catch(err => {
              // The server is not yet available.
              if ((err.code && err.code === 'ECONNREFUSED')) {
                  return pingAfter(hosts, backoff);
              }
  
              // Altought it is returning an error, the server is available.
              if (err.info && err.info.code) {
                  return;
              }
  
              throw err;
          });
  };
  
  exports.ping = ping;
  