_onProcessExit() {
    if (!this.pool) {
      return Promise.resolve();
    }

    return this.pool.drain().then(() => {
      debug('connection drain due to process exit');
      return this.pool.clear();
    });
  }
/**
   * Handler which executes on process exit or connection manager shutdown
   *
   * @private
   * @returns {Promise}
   */
Handler which executes on process exit or connection manager shutdown
@private
@returns {Promise}
Handler which executes on process exit or connection manager shutdown @private @returns { Promise }
_onProcessExit() {
    if (!this.pool) {
      return Promise.resolve();
    }
    return this.pool.drain().then(() => {
      debug('connection drain due to process exit');
      return this.pool.clear();
    });
  }
_onProcessExit ( ) { if ( ! this . pool ) { return Promise . resolve ( ) ; } return this . pool . drain ( ) . then ( ( ) => { debug ( 'connection drain due to process exit' ) ; return this . pool . clear ( ) ; } ) ; }
Handler which executes on process exit or connection manager shutdown
 @private
 @returns {Promise}
Handler which executes on process exit or connection manager shutdown @private @returns { Promise }