singleflight

Request deduplication for Gleam.

Concurrent requests for the same key are only execute once, all calls share the same result without repeated work.

Install

gleam add singleflight

Usage

import gleam/io
import gleam/erlang/process
import gleam/otp/actor
import singleflight

pub fn main() -> Nil {
  let name = process.new_name("singleflight")
  let config = singleflight.config(1_000, 1_000)

  let assert Ok(actor.Started(data: server, ..)) =
    singleflight.start(config, name)

  let value =
    case singleflight.fetch(server, "key", fn(key) { key <> "-value" }) {
      Ok(value) -> value
      Error(singleflight.Crashed) -> panic as "singleflight worker crashed"
      Error(singleflight.TimedOut) -> panic as "singleflight request timed out"
    }

  io.debug(value)
}

Errors

fetch returns Error(singleflight.Crashed) if the singleflight actor or the worker process exits before producing a value.

fetch returns Error(singleflight.TimedOut) if no reply arrives within fetch_timeout_ms.