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
$ npm install --save wrr
Related to the NGINX example above
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'Returns: Function
Returns the function that should be used to select from your items.
You should only call wrr when your items change.
Type: Array
The candidates for selection, each of which must be an object of Weighted shape:
interface Weighted<T> {
/** 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.
MIT © Luke Edwards