https://github.com/discord/semaphore

Fast semaphore using ETS.
https://github.com/discord/semaphore

elixir erlang locks semaphore

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Fast semaphore using ETS.

• Host: GitHub
• URL: https://github.com/discord/semaphore
• Owner: discord
• License: mit
• Created: 2017-02-15T20:59:33.000Z (almost 8 years ago)
• Default Branch: master
• Last Pushed: 2024-06-07T09:10:33.000Z (8 months ago)
• Last Synced: 2025-01-15T14:21:27.016Z (7 days ago)
• Topics: elixir, erlang, locks, semaphore
• Language: Elixir
• Homepage:
• Size: 12.7 KB
• Stars: 745
• Watchers: 191
• Forks: 49
• Open Issues: 5
• Metadata Files:
  • Readme: README.md
  • License: LICENSE

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README

        
# Semaphore

[![Master](https://travis-ci.org/discordapp/semaphore.svg?branch=master)](https://travis-ci.org/discordapp/semaphore)

[![Hex.pm Version](http://img.shields.io/hexpm/v/semaphore.svg?style=flat)](https://hex.pm/packages/semaphore)

Programming in Erlang and Elixir usually allows for no locking since the VM essentially handles it for you when

communicating between processes. However, what about the situation when you have thousands of processes attempting

to interact with a single resource such as a process? Usually they will overload the process and explode the

message queue. ETS is the Swiss Army knife of the Erlang VM and can be applied to this problem. By using `:ets.update_counter`

and `:write_concurrency` we can achieve a **fast** low contention semaphore on ETS.

## Usage

Add it to `mix.exs`

```elixir

defp deps do

  [{:semaphore, "~> 1.3"}]

end

```

Then just use it like a semaphore in any other language.

```elixir

if Semaphore.acquire(:test, 1) do

  IO.puts "acquired"

  Semaphore.release(:test)

end

case Semaphore.call(:test, 1, fn -> :ok end) do

  :ok ->

    IO.puts "success"

  {:error, :max} ->

    IO.puts "too many callers"

end

```

## License

Semaphore is released under [the MIT License](LICENSE).

Check [LICENSE](LICENSE) file for more information.