FunPool

Limits the number of concurrent executions of anonymous functions.

FunPool is a thin, easy-to-use wrapper around NimblePool. It is designed for scenarios where you need to limit concurrency for arbitrary blocks of code without the overhead of defining custom worker modules.

Installation

Add fun_pool to your list of dependencies in mix.exs:

def deps do
  [
    {:fun_pool, "~> 1.0"}
  ]
end

Usage

1. Start the pool

Start the pool in your supervision tree. You must provide a :name and can optionally provide a :size (defaults to 5).

children = [
  FunPool.child_spec(name: MyPool, size: 10)
]

Supervisor.start_link(children, strategy: :one_for_one)

2. Run functions in the pool

Pass the pool name and an anonymous function to FunPool.run/3.

FunPool.run(MyPool, fn ->
  # This code is execution-limited by the pool size
  :ok = do_some_heavy_lifting()
end)

3. Handling Timeouts

By default, run/3 will wait indefinitely for a worker. You can specify a timeout in milliseconds:

try do
  FunPool.run(MyPool, fn -> :ok end, 5000)
catch
  :exit, {:timeout, _} ->
    IO.puts("Pool was too busy!")
end

How it works

FunPool implements the NimblePool behaviour. Each "worker" in the pool is essentially a placeholder that represents a concurrency slot. When you call run/3, it checks out a worker, executes your function in the calling process, and then checks the worker back in.

This approach is extremely lightweight as it doesn't involve moving large amounts of data between processes; the function runs in the process that calls run/3.

License

MIT License - see the LICENSE file for details.