CP-28369: Remove Unixext.daemonize (#6026)

Last usage of `Unixext.daemonize` was in `cdrommon`, drop it and move
the daemon to be fully handled by systemd (instead of `type=forking`).

`cdrommon` service is only started by storage scripts, and I'm not sure
if it's tested at all, but these changes pass BST+BVT.

ocaml/cdrommon/cdrommon.ml

@@ -63,6 +63,5 @@ let () =
     Printf.eprintf "usage: %s <cdrompath>\n" Sys.argv.(0) ;
     exit 1
   ) ;
-  Xapi_stdext_unix.Unixext.daemonize () ;
   (* check every 2 seconds *)
   check 2 Sys.argv.(1)

ocaml/libs/xapi-stdext/lib/xapi-stdext-unix/unixext.ml

@@ -94,27 +94,6 @@ let with_file file mode perms f =
     (fun () -> f fd)
     (fun () -> Unix.close fd)
 
-(* !! Must call this before spawning any threads !! *)
-
-(** daemonize a process *)
-let daemonize () =
-  match Unix.fork () with
-  | 0 -> (
-      if Unix.setsid () == -1 then
-        failwith "Unix.setsid failed" ;
-      match Unix.fork () with
-      | 0 ->
-          with_file "/dev/null" [Unix.O_WRONLY] 0 (fun nullfd ->
-              Unix.close Unix.stdin ;
-              Unix.dup2 nullfd Unix.stdout ;
-              Unix.dup2 nullfd Unix.stderr
-          )
-      | _ ->
-          exit 0
-    )
-  | _ ->
-      exit 0
-
 exception Break
 
 let lines_fold f start input =

ocaml/libs/xapi-stdext/lib/xapi-stdext-unix/unixext.mli

@@ -30,8 +30,6 @@ val pidfile_write : string -> unit
 
 val pidfile_read : string -> int option
 
-val daemonize : unit -> unit
-
 val with_file :
      string
   -> Unix.open_flag list
@@ -262,7 +260,7 @@ val test_open : int -> unit
   to [Xapi_stdext_unix.Unixext.select] that use file descriptors, because such calls will then immediately fail.
 
   This assumes that [ulimit -n] has been suitably increased in the test environment.
-  
+
   Can only be called once in a program, and will raise an exception otherwise.
 
   The file descriptors will stay open until the program exits.

ocaml/networkd/bin/networkd.ml

@@ -224,15 +224,11 @@ let () =
       ~rpc_fn:(Idl.Exn.server Network_server.S.implementation)
       ()
   in
-  Xcp_service.maybe_daemonize
-    ~start_fn:(fun () ->
-      Debug.set_facility Syslog.Local5 ;
-      (* We should make the following configurable *)
-      Debug.disable "http" ;
-      handle_shutdown () ;
-      Debug.with_thread_associated "main" start server
-    )
-    () ;
+  Debug.set_facility Syslog.Local5 ;
+  (* We should make the following configurable *)
+  Debug.disable "http" ;
+  handle_shutdown () ;
+  Debug.with_thread_associated "main" start server ;
   let module Daemon = Xapi_stdext_unix.Unixext.Daemon in
   if Daemon.systemd_notify Daemon.State.Ready then
     ()

ocaml/squeezed/src/squeezed.ml

@@ -110,9 +110,6 @@ let _ =
       ~rpc_fn:(Idl.Exn.server S.implementation)
       ()
   in
-  maybe_daemonize () ;
-  (* NB Initialise the xenstore connection after daemonising, otherwise we lose
-     our connection *)
   let _ = Thread.create Memory_server.record_boot_time_host_free_memory () in
   let rpc_server = Thread.create Xcp_service.serve_forever server in
   Memory_server.start_balance_thread balance_check_interval ;

ocaml/xapi-idl/lib/xcp_service.ml

@@ -31,10 +31,6 @@ let log_destination = ref "syslog:daemon"
 
 let log_level = ref Syslog.Debug
 
-let daemon = ref false
-
-let have_daemonized () = Unix.getppid () = 1
-
 let common_prefix = "org.xen.xapi."
 
 let finally f g =
@@ -196,11 +192,6 @@ let common_options =
     , (fun () -> !log_destination)
     , "Where to write log messages"
     )
-  ; ( "daemon"
-    , Arg.Bool (fun x -> daemon := x)
-    , (fun () -> string_of_bool !daemon)
-    , "True if we are to daemonise"
-    )
   ; ( "disable-logging-for"
     , Arg.String
         (fun x ->
@@ -552,8 +543,6 @@ let http_handler call_of_string string_of_response process s =
         Response.write (fun _t -> ()) response oc
   )
 
-let ign_int (t : int) = ignore t
-
 let default_raw_fn rpc_fn s =
   http_handler Xmlrpc.call_of_string Xmlrpc.string_of_response rpc_fn s
 
@@ -635,52 +624,6 @@ let serve_forever = function
       let rec forever () = Thread.delay 3600. ; forever () in
       forever ()
 
-let pidfile_write filename =
-  let fd =
-    Unix.openfile filename [Unix.O_WRONLY; Unix.O_CREAT; Unix.O_TRUNC] 0o640
-  in
-  finally
-    (fun () ->
-      let pid = Unix.getpid () in
-      let buf = string_of_int pid ^ "\n" |> Bytes.of_string in
-      let len = Bytes.length buf in
-      if Unix.write fd buf 0 len <> len then
-        failwith "pidfile_write failed"
-    )
-    (fun () -> Unix.close fd)
-
-(* Cf Stevens et al, Advanced Programming in the UNIX Environment,
-   Section 13.3 *)
-let daemonize ?start_fn () =
-  if not (have_daemonized ()) then
-    ign_int (Unix.umask 0) ;
-  match Unix.fork () with
-  | 0 -> (
-      if Unix.setsid () == -1 then failwith "Unix.setsid failed" ;
-      Sys.set_signal Sys.sighup Sys.Signal_ignore ;
-      match Unix.fork () with
-      | 0 ->
-          Option.iter (fun fn -> fn ()) start_fn ;
-          Unix.chdir "/" ;
-          mkdir_rec (Filename.dirname !pidfile) 0o755 ;
-          pidfile_write !pidfile ;
-          let nullfd = Unix.openfile "/dev/null" [Unix.O_RDWR] 0 in
-          Unix.dup2 nullfd Unix.stdin ;
-          Unix.dup2 nullfd Unix.stdout ;
-          Unix.dup2 nullfd Unix.stderr ;
-          Unix.close nullfd
-      | _ ->
-          exit 0
-    )
-  | _ ->
-      exit 0
-
-let maybe_daemonize ?start_fn () =
-  if !daemon then
-    daemonize ?start_fn ()
-  else
-    Option.iter (fun fn -> fn ()) start_fn
-
 let cli ~name ~doc ~version ~cmdline_gen =
   let default = Term.(ret (const (fun _ -> `Help (`Pager, None)) $ const ())) in
   let version =

ocaml/xapi-idl/lib/xcp_service.mli

@@ -54,14 +54,8 @@ val make :
 
 val serve_forever : server -> unit
 
-val daemon : bool ref
-
 val loglevel : unit -> Syslog.level
 
-val daemonize : ?start_fn:(unit -> unit) -> unit -> unit
-
-val maybe_daemonize : ?start_fn:(unit -> unit) -> unit -> unit
-
 val cli :
      name:string
   -> doc:string

ocaml/xapi-storage-script/main.ml

@@ -2043,11 +2043,6 @@ let _ =
   in
   configure2 ~name:"xapi-script-storage" ~version:Xapi_version.version
     ~doc:description ~resources ~options () ;
-  if !Xcp_service.daemon then (
-    Xcp_service.maybe_daemonize () ;
-    use_syslog := true ;
-    info "Daemonisation successful."
-  ) ;
   let run () =
     let ( let* ) = ( >>= ) in
     let* observer_enabled = observer_is_component_enabled () in

ocaml/xapi/xapi_main.ml

@@ -22,8 +22,6 @@ let _ =
   Debug.set_facility Syslog.Local5 ;
   Sys.enable_runtime_warnings true ;
   init_args () ;
-  (* need to read args to find out whether to daemonize or not *)
-  Xcp_service.maybe_daemonize () ;
   (* Disable logging for the module requested in the config *)
   List.iter
     (fun m ->

ocaml/xcp-rrdd/bin/rrdd/xcp_rrdd.ml

@@ -747,7 +747,6 @@ let _ =
   debug "Reading configuration file .." ;
   Xcp_service.configure2 ~name:Sys.argv.(0) ~version:Xapi_version.version ~doc
     ~options () ;
-  Xcp_service.maybe_daemonize () ;
   debug "Starting the HTTP server .." ;
   (* Eventually we should switch over to xcp_service to declare our services,
      but since it doesn't support HTTP GET and PUT we keep the old code for now.

ocaml/xenopsd/lib/xenopsd.ml

@@ -461,7 +461,6 @@ let main backend =
   (* we need to catch this to make sure at_exit handlers are triggered. In
      particuar, triggers for the bisect_ppx coverage profiling *)
   let signal_handler n = debug "caught signal %d" n ; exit 0 in
-  Xcp_service.maybe_daemonize () ;
   Sys.set_signal Sys.sigpipe Sys.Signal_ignore ;
   Sys.set_signal Sys.sigterm (Sys.Signal_handle signal_handler) ;
   Xenops_utils.set_fs_backend

ocaml/xenopsd/xc/xenops_xc_main.ml

@@ -37,13 +37,7 @@ let check_domain0_uuid () =
     ]
   in
   let open Ezxenstore_core.Xenstore in
-  with_xs (fun xs -> List.iter (fun (k, v) -> xs.Xs.write k v) kvs) ;
-  if !Xcp_service.daemon then
-    (* before daemonizing we need to forget the xenstore client because the
-       background thread will be gone after the fork().
-       Note that this leaks a thread.
-    *)
-    forget_client ()
+  with_xs (fun xs -> List.iter (fun (k, v) -> xs.Xs.write k v) kvs)
 
 let make_var_run_xen () =
   Xapi_stdext_unix.Unixext.mkdir_rec Device_common.var_run_xen_path 0o0755

quality-gate.sh

@@ -40,7 +40,7 @@ mli-files () {
 }
 
 structural-equality () {
-  N=11
+  N=9
   EQ=$(git grep -r --count ' == ' -- '**/*.ml' ':!ocaml/sdk-gen/**/*.ml' | cut -d ':' -f 2 | paste -sd+ - | bc)
   if [ "$EQ" -eq "$N" ]; then
     echo "OK counted $EQ usages of ' == '"

scripts/cdrommon@.service

@@ -2,6 +2,4 @@
 Description=Monitor CDROM of %I
 
 [Service]
-Type=forking
-GuessMainPID=no
 ExecStart=/opt/xensource/libexec/cdrommon /dev/xapi/cd/%I