wrr  

> A tiny (148B) weighted round robin utility

At its core, a "weighted round robin" (wrr) will skew a list's random selection towards list items that have more _weight_ given to them.
This is generally seen in load-balancing contexts, but wrr is not at all limited to that scenario.

From the NGINX glossary:

> Weighted round robin – A weight is assigned to each server based on criteria chosen by the site administrator; the most commonly used criterion is the server’s traffic‑handling capacity. The higher the weight, the larger the proportion of client requests the server receives. If, for example, server A is assigned a weight of 3 and server B a weight of 1, the load balancer forwards 3 requests to server A for each 1 it sends to server B.

This module exposes three module definitions:

* ES Module: dist/wrr.mjs
* CommonJS: dist/wrr.js
* UMD: dist/wrr.min.js

Install

``
$ npm install --save wrr
`




Usage

> Related to the NGINX example above

`js
import wrr from 'wrr';

const servers = [
// 3x capacity of B; picked 3x more often than B
{ item: 'Server A', weight: 3 },
// our "base unit" for comparison
{ item: 'Server B', weight: 1 },
// 2x capacity of B; picked 2x more often than B
{ item: 'Server C', weight: 2 },
];

// Create reusable instance
const toPickServer = wrr(servers);

toPickServer(); //=> 'Server A'
toPickServer(); //=> 'Server C'
toPickServer(); //=> 'Server A'
toPickServer(); //=> 'Server A'
toPickServer(); //=> 'Server A'
toPickServer(); //=> 'Server A'
toPickServer(); //=> 'Server C'
toPickServer(); //=> 'Server A'
toPickServer(); //=> 'Server A'
toPickServer(); //=> 'Server B'
toPickServer(); //=> 'Server C'
toPickServer(); //=> 'Server A'
`




API

$3


Returns: Function

Returns the function that should be used to select from your items.
You should only call wrr when your items change.

#### items
Type: Array

The candidates for selection, each of which must be an object of Weighted shape:

`js
interface Weighted {
/* The item's weight (non-decimal) /
weight: number;
/* The array item /
item: T;
}
`

You can use any rubric for your weight value; however, only whole-number integers are allowed.

The item` key can hold _any_ value you'd like. This is what's returned to you directly.

License

MIT © Luke Edwards