Method _refresh

lib/control-connection.js:455–510

* Acquires a new connection and refreshes topology and keyspace metadata. * When it fails obtaining a connection and there aren't any more hosts, it schedules reconnection. * When it fails obtaining the metadata, it marks connection and/or host unusable and retries using the same

(hostIterator)

   * @param {Iterator<Host>} [hostIterator]
   */
  async _refresh(hostIterator) {
    if (this._isShuttingDown) {
      this.log('info', 'The ControlConnection will not be refreshed as the Client is being shutdown');
      return;
    }

    // Reset host and connection
    this.host = null;
    this.connection = null;

    try {
      if (!hostIterator) {
        this.log('info', 'Trying to acquire a connection to a new host');
        this._triedHosts = {};
        hostIterator = await promiseUtils.newQueryPlan(this._profileManager.getDefaultLoadBalancing(), null, null);
      }

      await this._refreshControlConnection(hostIterator);
    } catch (err) {
      // There was a failure obtaining a connection or during metadata retrieval
      this.log('error', 'ControlConnection failed to acquire a connection', err);

      if (!this._isShuttingDown) {
        const delay = this._reconnectionSchedule.next().value;
        this.log('warning', `ControlConnection could not reconnect, scheduling reconnection in ${delay}ms`);
        setTimeout(() => this._refresh(), delay);
        this.emit('newConnection', err);
      }

      return;
    }

    this.log('info',`ControlConnection connected to ${this.connection.endpointFriendlyName}`);

    try {
      await this._refreshHosts(false, true);

      await this._registerToConnectionEvents();
    } catch (err) {
      this.log('error', 'ControlConnection failed to retrieve topology and keyspaces information', err);
      this._triedHosts[this.connection.endpoint] = err;

      if (err.isSocketError && this.host) {
        this.host.removeFromPool(this.connection);
      }

      // Retry the whole thing with the same query plan
      return await this._refresh(hostIterator);
    }

    this._reconnectionSchedule = this._reconnectionPolicy.newSchedule();
    this._setHealthListeners(this.host, this.connection);
    this.emit('newConnection', null, this.connection, this.host);

    this.log('info', `ControlConnection connected to ${this.connection.endpointFriendlyName} and up to date`);
  }

  /**