EZ-FIFOs with LWT

Objectives

Read FileDescr FIFOs quickly.

EZ to do, so it should stay EZ to use.

I used LWT because it is cool and compatible with others libs (Async/EIO)

Usage

Background-read

let () =
  Ezfifos_lwt.background_read ~callback:(fun s -> print_endline s; Lwt.return_unit) "/path/to/fifo"

The background_read function will declare a passive thread that will read any content at /path/to/fifo and bind a callback to the read result.

The callback is called to every LINE read in the FIFO.

This is a passive thread, binary can live its life, this is not a server, it will stop if there is nothing else to do.

For a server use listen

Listen-passive server

let stop = ref false
let callback s = print_endline s; Lwt.return_unit

let server () = Ezfifos_lwt.listen ~stop ~callback "/path/to/fifo"

let () =
  Lwt_main.run Lwt.(join [ server (); ... ])

The listen function will declare a non-stopping, non-blockant server that will bind callback to every LINE read in the FIFO.

It will run on the FIFO until it is empty and then wait for more content.

It will be closed at_exit or when calling close path or stop_all ().

You can stop it by switching the stop ref to true, stop is a non mandatory value, if None, server will run for ever

Read once

let () =
  Lwt_main.run
    Ezfifos_lwt.(read_once ~callback:(fun s -> print_endline s; Lwt.return_unit) "/path/to/fifo")

It will empty FIFO once, bind result to callback then stop, similar as Lwt_io.read & FileUtils.rm but slower, but available.

Write

let () =
  Lwt_main.run Ezfifos_lwt.(write ~path:"/path/to/fifo" "datas")

It will write datas to FIFO, similar to Printf.fprintf, doubted to add the fun, but at least it is using cool Lwt_io content.

Good practices

You can find client/server exemple with common Protocol wrapping good practices.

Notes

It scales (tested with millions of R/W in CrossinG® main workload)

BUT I assumed you won't bind hundred thousands of FIFOs so Fifos_database is just a simple List of path/thread retainer,

You may prefer to rewrite Db module with Hmap of Hashtabl if you need to manage a lot of fifos, less memory efficiant but scales

Quickdemo

$ dune exec bin/demo.exe ~/Documents/test_files/test_fifo