Method getNextConnection

lib/request-handler.js:74–110

* Gets a connection from the next host according to the query plan or throws a NoHostAvailableError. * @returns {{host, connection}} * @throws {NoHostAvailableError}

()

   * @throws {NoHostAvailableError}
   */
  getNextConnection() {
    let host;
    let connection;
    const iterator = this._hostIterator;

    // Get a host that is UP in a sync loop
    while (true) {
      const item = iterator.next();
      if (item.done) {
        throw new errors.NoHostAvailableError(this.triedHosts);
      }

      host = item.value;

      // Set the distance relative to the client first
      const distance = this.client.profileManager.getDistance(host);
      if (distance === types.distance.ignored) {
        //If its marked as ignore by the load balancing policy, move on.
        continue;
      }

      if (!host.isUp()) {
        this.triedHosts[host.address] = 'Host considered as DOWN';
        continue;
      }

      try {
        connection = host.borrowConnection();
        this.triedHosts[host.address] = null;
        break;
      } catch (err) {
        this.triedHosts[host.address] = err;
      }
    }

    return { connection, host };
  }

  /**
   * Gets an available connection and sends the request