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https://github.com/lukeed/wrr
A tiny (148B) weighted round robin utility
https://github.com/lukeed/wrr
Last synced: 28 days ago
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A tiny (148B) weighted round robin utility
- Host: GitHub
- URL: https://github.com/lukeed/wrr
- Owner: lukeed
- License: mit
- Created: 2019-10-16T23:40:02.000Z (about 5 years ago)
- Default Branch: master
- Last Pushed: 2019-11-27T00:00:17.000Z (about 5 years ago)
- Last Synced: 2024-10-31T10:37:42.562Z (about 1 month ago)
- Language: JavaScript
- Size: 10.7 KB
- Stars: 164
- Watchers: 5
- Forks: 2
- Open Issues: 0
-
Metadata Files:
- Readme: readme.md
- License: license.md
Awesome Lists containing this project
- awesome-crafted-nodejs - wrr - A tiny (148B) weighted round robin utility (Packages / Others)
- awesome-list - wrr
README
# wrr [](https://github.com/lukeed/wrr/actions) [](https://codecov.io/gh/lukeed/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](https://www.nginx.com/resources/glossary/round-robin-load-balancing/):
> **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
### wrr(items)
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](https://lukeed.com)