aws-kcl/lib/kcl/action_handler.js

Kinesis Client Libray (KCL) in Node.js.

/***
Copyright 2019 Amazon.com, Inc. or its affiliates. All Rights Reserved.
SPDX-License-Identifier: Apache-2.0
***/

'use strict';

/**
 * @fileoverview
 * Marshals and unmarshals actions and delegates them back and forth between the I/O handler
 * that talks to the MultiLangDaemon and the KCL manager.
 */

var EventEmitter = require('events').EventEmitter;
var util = require('util');

/**
 * Creates an instance of the action handler.
 * @class ActionHandler
 * @param {IOHandler} ioHandler - I/O handler instance that communicates with the MultiLangDaemon.
 */
function ActionHandler(ioHandler) {
  this._ioHandler = ioHandler;
  this._onIOLineCallback = this._onIOLine.bind(this);
  this._onIOCloseCallback = this._onIOClose.bind(this);
  this._ioHandler.on('line', this._onIOLineCallback);
  this._ioHandler.on('close', this._onIOCloseCallback);
}

/** @extends EventEmitter */
util.inherits(ActionHandler, EventEmitter);

/**
 * Frees up any resources held by this instance.
 */
ActionHandler.prototype.destroy = function() {
  this._ioHandler.removeListener('line', this._onIOLineCallback);
  this._ioHandler.removeListener('close', this._onIOCloseCallback);
};

/**
 * Sends an action to the MultiLangDaemon.
 * @param {object} action - Action to send to the MultiLangDaemon.
 * @param {callback} callback - Callback that will be invoked when the action is sent to the MultiLangDaemon.
 */
ActionHandler.prototype.sendAction = function(action, callback) {
  this._ioHandler.writeLine(JSON.stringify(action), callback);
};

/**
 * Event handler when a new line is received from the MultiLangDaemon through the I/O handler.
 * @param {string} line - New line received by IO handler.
 * @private
 */
ActionHandler.prototype._onIOLine = function(line) {
  if (line) {
    var action = JSON.parse(line);
    if (!action || !action.action) {
      this._ioHandler.writeError(util.format('Invalid action received: %s', line));
      return;
    }
    this.emit('action', action);
  }
};

/**
 * Event handler for the I/O close event. Following this event, no new lines will be received from the I/O handler.
 * @private
 */
ActionHandler.prototype._onIOClose = function() {
  this.emit('end');
};


/** @exports kcl/ActionHandler */
module.exports = ActionHandler;