server: Simplify 'get_number_of_connected'

This code was possibly intended to detect connections that are never
closed. But it is currently unused and is tricky to reason about in the
context of the migration to direct-style.

Author: Julow

src/server/ocsigen_cohttp.ml

@@ -22,29 +22,10 @@ let _print_request fmt request =
 
 let connections = Hashtbl.create 256
 
-let ( get_number_of_connected
-    , incr_connected
-    , decr_connected
-    , _wait_fewer_connected )
-  =
+let get_number_of_connected, incr_connected, decr_connected =
+  (* TODO: Use Atomic once the 4.12 dependency is acceptable. *)
   let connected = ref 0 in
-  let maxr = ref (-1000) in
-  let mvar = Lwt_mvar.create_empty () in
-  ( (fun () -> !connected)
-  , (fun n -> connected := !connected + n)
-  , (fun () ->
-      let c = !connected in
-      connected := c - 1;
-      if !connected < 0 then exit 1;
-      if c = !maxr
-      then (
-        Lwt_log.ign_warning ~section "Number of connections now ok";
-        maxr := -1000;
-        Lwt_mvar.put mvar ())
-      else Lwt.return ())
-  , fun max ->
-      maxr := max;
-      Lwt_mvar.take mvar )
+  (fun () -> !connected), (fun () -> incr connected), fun () -> decr connected
 
 exception Ocsigen_is_dir of (Ocsigen_request.t -> Uri.t)
 
@@ -116,7 +97,7 @@ let handler ~ssl ~address ~port ~connector (flow, conn) request body =
     with Not_found ->
       let ((connection_closed, _) as p) = Lwt.wait () in
       Hashtbl.add connections conn p;
-      incr_connected 1;
+      incr_connected ();
       connection_closed
   in
   let handle_error exn =
@@ -212,7 +193,7 @@ let conn_closed (_flow, conn) =
       (Cohttp.Connection.to_string conn);
     Lwt.wakeup (snd (Hashtbl.find connections conn)) ();
     Hashtbl.remove connections conn;
-    Lwt.async decr_connected
+    decr_connected ()
   with Not_found -> ()
 
 let stop, stop_wakener = Lwt.wait ()