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type status =
| Started of
{ daemon_info : string
; pid : Pid.t
}
| Already_running of
{ daemon_info : string
; pid : Pid.t
}
| Finished
let retry ?message ?(count = 100) f =
let rec loop = function
| x when x >= count ->
Result.Error
(Printf.sprintf "too many retries (%i)" x
^
match message with
| None -> ""
| Some msg -> ": " ^ msg)
| x -> (
match f () with
| Some v -> Result.Ok v
| None ->
Unix.sleepf 0.1;
loop (x + 1))
in
loop 0
let make_beacon path =
Option.iter ~f:Path.mkdir_p (Path.parent path);
let p = Path.to_string path in
let fd = Unix.openfile p [ Unix.O_RDWR; Unix.O_CREAT ] 0o600 in
if Fcntl.lock_try fd Fcntl.Write then
Result.Ok fd
else
Result.Error "already running"
let seal_beacon path fd contents =
let p = Path.to_string path
and length = String.length contents in
if Unix.write fd (Bytes.of_string contents) 0 length <> length then (
Unix.close fd;
Result.Error
(Printf.sprintf "couldn't write whole endpoint to port file \"%s\"" p)
) else (
Fcntl.lock fd Fcntl.Read;
Result.Ok fd
)
let check_beacon ?(close = true) p =
match Result.try_with (fun () -> Unix.openfile p [ Unix.O_RDONLY ] 0o600) with
| Result.Ok fd ->
let f () =
let open Result.O in
retry (fun () ->
match Fcntl.lock_get fd Fcntl.Write with
| None -> Some None
| Some (Fcntl.Read, pid) -> Some (Some pid)
| Some (Fcntl.Write, _) -> None)
>>| Option.map ~f:(fun pid ->
(Io.read_all (Unix.in_channel_of_descr fd), pid, fd))
and finally () = if close then Unix.close fd in
Exn.protect ~f ~finally
| Result.Error (Unix.Unix_error (Unix.ENOENT, _, _)) -> Result.Ok None
| Result.Error (Unix.Unix_error (c, _, _)) ->
Result.Error
(Printf.sprintf "unable to open %s: %s" p (Unix.error_message c))
| Result.Error _ -> Result.Error (Printf.sprintf "unable to open %s" p)
let daemonize ?workdir ?(foreground = false) beacon
(f : (daemon_info:string -> unit) -> unit) =
let f fd =
let f () =
f (fun ~daemon_info -> ignore (seal_beacon beacon fd daemon_info))
and finally () = Unix.truncate (Path.to_string beacon) 0 in
Exn.protect ~f ~finally
in
let path = Path.to_string beacon in
let path =
match workdir with
| Some workdir when Filename.is_relative path ->
Filename.concat (Path.to_string workdir) path
| _ -> path
in
let open Result.O in
check_beacon path >>= function
| None ->
if foreground then (
let+ fd = make_beacon beacon in
f fd;
Finished
) else if Unix.fork () = 0 then (
ignore (Unix.setsid ());
Sys.set_signal Sys.sighup Sys.Signal_ignore;
Sys.set_signal Sys.sigpipe Sys.Signal_ignore;
if Unix.fork () = 0 then (
Option.iter
~f:(fun p ->
Path.mkdir_p p;
Unix.chdir (Path.to_string p))
workdir;
let null = open_in "/dev/null"
and out = open_out "stdout"
and err = open_out "stderr" in
Unix.dup2
(Unix.descr_of_in_channel null)
(Unix.descr_of_in_channel stdin);
Unix.dup2
(Unix.descr_of_out_channel out)
(Unix.descr_of_out_channel stdout);
Unix.dup2
(Unix.descr_of_out_channel err)
(Unix.descr_of_out_channel stderr);
close_in null;
close_out out;
close_out err;
ignore (Unix.umask 0);
ignore
(let+ fd = make_beacon beacon in
f fd)
);
exit 0
) else
let open Result.O in
let* fd =
retry
~message:
(Printf.sprintf "waiting for beacon file \"%s\" to be created" path)
(fun () ->
try Some (Unix.openfile path [ Unix.O_RDONLY ] 0o600) with
| Unix.Unix_error (Unix.ENOENT, _, _) -> None)
in
let+ daemon_info, pid =
retry
~message:
(Printf.sprintf "waiting for beacon file \"%s\" to be locked" path)
(fun () ->
match Fcntl.lock_get fd Fcntl.Write with
| Some (Fcntl.Read, pid) ->
Some (Io.read_all (Unix.in_channel_of_descr fd), pid)
| _ -> None)
in
Started { daemon_info; pid = Pid.of_int pid }
| Some (daemon_info, pid, _) ->
Result.Ok (Already_running { daemon_info; pid = Pid.of_int pid })
let stop beacon =
let open Result.O in
check_beacon ~close:false (Path.to_string beacon) >>= function
| None -> Result.Error "not running"
| Some (_, pid, fd) -> (
let kill signal =
Unix.kill pid signal;
retry ~message:(Printf.sprintf "waiting for daemon to stop (PID %i)" pid)
(fun () -> Option.some_if (Fcntl.lock_get fd Fcntl.Write = None) ())
in
match kill Sys.sigterm with
| Error _ ->
kill Sys.sigkill
| ok -> ok)