# glimit

[![Package Version](https://img.shields.io/hexpm/v/glimit)](https://hex.pm/packages/glimit)
[![Hex Docs](https://img.shields.io/badge/hex-docs-ffaff3)](https://hexdocs.pm/glimit/glimit.html)
[![test](https://github.com/nootr/glimit/actions/workflows/test.yml/badge.svg)](https://github.com/nootr/glimit/actions/workflows/test.yml)

A simple, framework-agnostic, in-memory rate limiter for Gleam. 💫


## Features

* ✨ Simple and easy to use.
* 📏 Rate limits based on any key (e.g. IP address, or user ID).
* 🪣 Uses a Token Bucket algorithm to rate limit requests.
* 🗄️ No back-end service needed; stores rate limit stats in-memory.


## Usage

A very minimalistic example of how to use `glimit` would be the following snippet:

```gleam
import glimit

let limiter =
  glimit.new()
  |> glimit.per_second(2)
  |> glimit.identifier(fn(x) { x })
  |> glimit.on_limit_exceeded(fn(_) { "Stop!" })

let func =
  fn(_) { "OK" }
  |> glimit.apply(limiter)

func("🚀") // "OK"
func("💫") // "OK"
func("💫") // "OK"
func("💫") // "Stop!"
func("🚀") // "OK"
func("🚀") // "Stop!"
```

More practical examples can be found in the `examples/` directory, such as Wisp and Mist server examples.


## Constraints

While the in-memory rate limiter is simple and easy to use, it does have an important constraint: it is scoped to the BEAM VM cluster it runs in. This means that if your application is running across multiple BEAM VM clusters, the rate limiter will not be shared between them.


## Performance

All rate limiter state is held in a single OTP actor. Each hit is one message to this actor, which performs the token bucket calculation inline.

* **Memory**: One dict entry per unique identifier. Idle identifiers (full token buckets) are automatically swept every 10 seconds.
* **Fail-open**: If the rate limiter actor is unavailable, the request is allowed through rather than rejected.


## Documentation

Further documentation can be found at <https://hexdocs.pm/glimit/glimit.html>.


## Contributing

Contributions like PR's, bug reports or suggestions are more than welcome! ♥️