SmoothWeightedRoundRobin.js

// original article: http://www.cnblogs.com/CodeBear/p/10508880.html
(()=>{
    class Node{
        constructor(name, weight){
            this.name = name;
            this.weight = weight;
            this.runtimeWeight = weight;
        }
    }

    class Pool{
        constructor(nodes){
            this.nodes = nodes;
            this.totalWeight = this.nodes.reduce((a,b)=>a+b.runtimeWeight, 0);
        }

        *selector(){
            while(true){
                // var currentWeight = this.nodes.map(n=>n.runtimeWeight);
                // 1. thoose the node with largest runtimeWeight
                var workingNode = this.nodes.reduce((a, n)=>n.runtimeWeight > a.runtimeWeight ? n : a, this.nodes[0]);
                // 2. update the selected node's runtimeWeight by subtract the total weight (which is a statuc value of sum of all weight of each nodes)
                workingNode.runtimeWeight -= this.totalWeight;
                // var adjustWeight = this.nodes.map(n=>n.runtimeWeight);
                // 3. update runtimeWeight of each node, by add its original weight onto it
                this.nodes.forEach(n=>n.runtimeWeight += n.weight);
                // console.log(`Request assigned to ${workingNode.name}    ${currentWeight}    ${adjustWeight}`);
                yield workingNode.name;
            }
        }
    }

    var p = new Pool([new Node(1, 5), new Node(2, 1), new Node(3, 1)]).selector();
    var counter = [0,0,0];
    for(var i=0;i<7000;i++){
        var id = p.next().value;
        counter[id-1] +=1;
    }
    console.log(counter);
})();