Hammer

A rate-limiter for Elixir, with pluggable storage backends.

New! Hammer-Plug

We've just released a new helper-library to make adding rate-limiting to your Phoenix (or other plug-based) application even easier: Hammer.Plug.

Installation

Hammer is available in Hex, the package can be installed by adding :hammer to your list of dependencies in mix.exs:

def deps do
  [
    {:hammer, "~> 6.1"}
  ]
end

Documentation

On HexDocs: https://hexdocs.pm/hammer/frontpage.html

The Tutorial is an especially good place to start.

Usage

Example:

defmodule MyApp.VideoUpload do

  def upload(video_data, user_id) do
    case Hammer.check_rate("upload_video:#{user_id}", 60_000, 5) do
      {:allow, _count} ->
        # upload the video, somehow
      {:deny, _limit} ->
        # deny the request
    end
  end

end

The Hammer module provides the following functions:

• check_rate(id, scale_ms, limit)
• check_rate_inc(id, scale_ms, limit, increment)
• inspect_bucket(id, scale_ms, limit)
• delete_buckets(id)

Backends are configured via Mix.Config:

config :hammer,
  backend: {Hammer.Backend.ETS, [expiry_ms: 60_000 * 60 * 4,
                                 cleanup_interval_ms: 60_000 * 10]}

See the Tutorial for more.

See the Hammer Testbed app for an example of using Hammer in a Phoenix application.

Available Backends

• Hammer.Backend.ETS (provided with Hammer for testing and dev purposes, not very good for production use)
• Hammer.Backend.Redis
• Hammer.Backend.Mnesia (beta)

Getting Help

If you're having trouble, either open an issue on this repo, or reach out to the maintainers (@shanekilkelly) on Twitter.

Acknowledgements

Hammer was inspired by the ExRated library, by grempe.

License

Copyright (c) 2017 Shane Kilkelly

This library is MIT licensed. See the LICENSE for details.