https://github.com/juergenhoetzel/ocaml-systemd

OCaml module for native access to the systemd facilities
https://github.com/juergenhoetzel/ocaml-systemd

journald ocaml socket-activation systemd

Last synced: 3 months ago
JSON representation

OCaml module for native access to the systemd facilities

• Host: GitHub
• URL: https://github.com/juergenhoetzel/ocaml-systemd
• Owner: juergenhoetzel
• Created: 2015-04-25T13:19:52.000Z (almost 10 years ago)
• Default Branch: master
• Last Pushed: 2022-11-20T12:08:16.000Z (about 2 years ago)
• Last Synced: 2023-04-23T05:46:48.045Z (almost 2 years ago)
• Topics: journald, ocaml, socket-activation, systemd
• Language: OCaml
• Size: 68.4 KB
• Stars: 23
• Watchers: 3
• Forks: 7
• Open Issues: 2
• Metadata Files:
  • Readme: README.md

Awesome Lists containing this project

README

        
# ocaml-systemd [![Build Status](https://api.travis-ci.org/juergenhoetzel/ocaml-systemd.svg)](https://travis-ci.org/juergenhoetzel/ocaml-systemd/)

OCaml library allowing interaction with systemd and journald

# Journald Usage

```OCaml

open Journald

let () = journal_send_message Priority.INFO "Hello";

	 (* compile and link its compilation units with option -g to get CODE_FILE and CODE_LINE entries*)

	 journal_send_message_loc Priority.INFO "Hello with location";

	 (* compile and link its compilation units with option -g *)

	 journal_send ["CUSTOM_FIELD", "CUSTOM_VALUE"];

	 journal_send_loc ["CUSTOM_FIELD", "CUSTOM_VALUE with location"];

```

## Performance

To get callstack info (required for the implicit

`CODE_FILE` and `CODE_LINE` entries) you need to build your

compilation units with

debugging information.

Getting the callstack at runtime also results in an performance overhead, so there a 2 groups of journal functions:

### Journal functions with location info

```OCaml

val journal_send_message_loc : Priority.t -> string -> unit

val journal_send_loc : (string * string) list -> unit

```

### Journal functions without location info

```OCaml

val journal_send : (string * string) list -> unit

val journal_send_message : Priority.t -> string -> unit

```

# Socket activation

No need for forking the process, binding/listening the sockets.

Also support for systemd watchdog functionality.

## Complete Example: Lwt echo server using socket activation

```Ocaml

open Daemon

open Daemon.State

open Lwt

open Lwt_unix

open Journald

let echo_server conn_fd =

  let in_channel = Lwt_io.of_fd ~mode:Lwt_io.input conn_fd in

  let out_channel = Lwt_io.of_fd ~mode:Lwt_io.output conn_fd in

  finalize (fun () -> Lwt_stream.iter_s (Lwt_io.write_line out_channel) (Lwt_io.read_lines in_channel))

	   (fun () -> close conn_fd)

let rec accept fd =

  Lwt_unix.accept (Lwt_unix.of_unix_file_descr fd)

  >>= (fun (conn_fd, _) ->

       async (fun _ -> echo_server conn_fd);

       accept fd)

let _ =

  (* Notify systemd software watchdog every second *)

  Lwt_engine.on_timer 1.0 true (fun _ -> notify Watchdog|>ignore);

  notify Ready |> ignore;

  match listen_fds () with

  | [] -> journal_send_message Priority.CRIT "No file descriptors passed by the system manager"

  | fd::_ -> journal_send_message Priority.INFO "socket activation succeded";

	     accept fd |> Lwt_main.run

```