/*
* Copyright 2016 IBM Corp.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
(function () {
var JavaWrapper = require(EclairJS_Globals.NAMESPACE + '/JavaWrapper');
var Logger = require(EclairJS_Globals.NAMESPACE + '/Logger');
var Utils = require(EclairJS_Globals.NAMESPACE + '/Utils');
var logger = Logger.getLogger("broadcast_Broadcast_js");
/**
* @classdesc
* A broadcast variable. Broadcast variables allow the programmer to keep a read-only variable
* cached on each machine rather than shipping a copy of it with tasks. They can be used, for
* example, to give every node a copy of a large input dataset in an efficient manner. Spark also
* attempts to distribute broadcast variables using efficient broadcast algorithms to reduce
* communication cost.
*
* Broadcast variables are created from a variable `v` by calling
* {@link module:eclairjs.SparkContext#broadcast}.
* The broadcast variable is a wrapper around `v`, and its value can be accessed by calling the
* `value` method. The interpreter session below shows this:
*
* After the broadcast variable is created, it should be used instead of the value `v` in any
* functions run on the cluster so that `v` is not shipped to the nodes more than once.
* In addition, the object `v` should not be modified after it is broadcast in order to ensure
* that all nodes get the same value of the broadcast variable (e.g. if the variable is shipped
* to a new node later).
*
* @example
* var b = sparkContext.broadcast([1,2]);
* var bc = b.value(); // bc = [1,2]
*
* @class
* @memberof module:eclairjs/broadcast
*/
var Broadcast = function (jvmObject) {
JavaWrapper.call(this, jvmObject);
};
Broadcast.prototype = Object.create(JavaWrapper.prototype);
Broadcast.prototype.constructor = Broadcast;
/**
* Get the broadcasted value.
* @returns {object}
*/
Broadcast.prototype.value = function () {
var javaObject = this.getJavaObject().value();
//return Utils.javaToJs(javaObject);
return JSON.parse(javaObject);
};
/**
* Delete cached copies of this broadcast on the executors. If the broadcast is used after
* this is called, it will need to be re-sent to each executor.
* @param {boolean} [blocking] Whether to block until unpersisting has completed
*/
Broadcast.prototype.unpersist = function (blocking) {
if (arguments[0]) {
this.getJavaObject().unpersist(blocking);
} else {
this.getJavaObject().unpersist();
}
};
/**
* Destroy all data and metadata related to this broadcast variable. Use this with caution;
* once a broadcast variable has been destroyed, it cannot be used again.
* This method blocks until destroy has completed
*/
Broadcast.prototype.destroy = function () {
this.getJavaObject().destroy();
};
/**
* @returns {string}
*/
Broadcast.prototype.toString = function () {
return this.getJavaObject().toString();
};
module.exports = Broadcast;
})();