WorkerRPC.js

WorkerRPC is a utility module for node.js which allows to distribute javascript workloads easily across multiple instances (e.g. to make use of multi-core cpus).

Quick Examples

Basic Worker used for examples:

//worker.js START

//pi(num,callback) will create NUM 2D-points in [0;1[
//and count how many have distance of 1 or less to origin.
//Returns that count via callback

function pi(num,callback){
    var insideCircle = 0;
    for(var i=0;i<num;i++) {
        var p = {x:Math.random(),y:Math.random()};
        if (p.x*p.x+p.y*p.y <= 1) {
            insideCircle++;
        }
    }
    console.log("Sample Pi Run finished (" + num + " trials)");
    callback(insideCircle);
}

//add this to worker.js to expose function add
require("workerrpc").wrap({
  pi:pi
});

Variant #1: Combining results via simple callbacks/RPC

//main.js START
var numOfTrials = 1000*1000;
var results = {insideCircle:0,total:0};

var workloads = [];
for(var i = 0;i < 10; i++) {
  workloads.push({
    //filename that will be forked in a child-process with wrapped object
        script: "worker.js",
        action: function(instance,params,finished) {

        //actual remote function to be called ("pi")
            instance.pi(numOfTrials,function(insideCircle) {
                results.insideCircle+=insideCircle;
                results.total+=numOfTrials;
                //call finished to make shure the worker is released from pool
                finished();
            });
        },

        //optional set of params to give worker
        params: {}
    });
}

//combine results once there are no more workers pending
var combineResults = function() {
  var piEstimate = 4*results.insideCircle/results.total;
  console.log("Estimated Pi to",piEstimate);
};

var numCores = require("os").cpus().length;
//create pool with maximum of numCores concurrent workers
var pool = require("workerrpc").pool(numCores, combineResults);

//add workload to pool and start working
pool.add(workloads);
//main.js END

Variant #2: Combine results using map/reduce

//main.js START
var numCores = require("os").cpus().length;

var workloads = require("../lib/workerrpc").createWorkload({
    maxParallel: numCores,
    script: "worker.js"
});

workloads.add(
    [{numOfTrials:1},{numOfTrials:2},{numOfTrials:4},{numOfTrials:8}]
);

workloads.
map(
    function doActualWork(workload,worker,next) {
        worker.pi(workload.numOfTrials,function(insideCircle) {
            next(null,{
                insideCircle:insideCircle,
                total:workload.numOfTrials
            });
        });
    }
).reduce(

    //WE ARE GOING TO SUM THE RESULTS UP, STARTING AT ZERO
    {insideCircle:0,total:0},

    //CODE TO ACTUALLY ADD RESULTS
    function sumSingleWorksResults(sum, current, next) {
        sum.insideCircle+=current.insideCircle;
        sum.total+=current.total;
        next(null,sum);
    },

    //FINISHED ADDING UP, PRINT RESULTS
    function printSumAndEstimate(err,sum) {
      var piEstimate = 4*sum.insideCircle/sum.total;
      console.log("Estimated Pi to be",piEstimate,"using",sum.total,"trials");
    }
);


//YOU CAN ADD WORKLOAD LATER ON
setTimeout(function() {
    workloads.add({numOfTrials:1000000});
},5000);
//main.js END

Download

The source is available for download from GitHub. Alternatively, you can install using Node Package Manager (npm):

npm install workerrpc

Test

Some basic tests are implemented using mocha.

mocha test -R spec

You can use npm test as well:

npm test