CP-52821: xapi_periodic_scheduler: use Mtime.span instead of Mtime.t

Avoids dealing with overflow

Signed-off-by: Edwin Török <[email protected]>

ocaml/xapi/ipq.ml

@@ -13,7 +13,7 @@
  *)
 (* Imperative priority queue *)
 
-type 'a event = {ev: 'a; time: Mtime.t}
+type 'a event = {ev: 'a; time: Mtime.span}
 
 type 'a t = {mutable size: int; mutable data: 'a event array}
 
@@ -49,7 +49,7 @@ let add h x =
   (* moving [x] up in the heap *)
   let rec moveup i =
     let fi = (i - 1) / 2 in
-    if i > 0 && Mtime.is_later d.(fi).time ~than:x.time then (
+    if i > 0 && Mtime.Span.is_longer d.(fi).time ~than:x.time then (
       d.(i) <- d.(fi) ;
       moveup fi
     ) else
@@ -76,7 +76,7 @@ let remove h s =
         let j' = j + 1 in
         if j' < n && d.(j').time < d.(j).time then j' else j
       in
-      if Mtime.is_earlier d.(j).time ~than:x.time then (
+      if Mtime.Span.is_shorter d.(j).time ~than:x.time then (
         d.(i) <- d.(j) ;
         movedown j
       ) else

ocaml/xapi/xapi_periodic_scheduler.ml

@@ -29,21 +29,13 @@ let (queue : t Ipq.t) = Ipq.create 50
 
 let lock = Mutex.create ()
 
-let add_span clock span =
-  match Mtime.add_span clock span with
-  | Some t ->
-      t
-  | None ->
-      raise
-        Api_errors.(Server_error (internal_error, ["clock overflow"; __LOC__]))
-
 let add_to_queue_span ?(signal = true) name ty start_span newfunc =
   with_lock lock (fun () ->
-      let ( ++ ) = add_span in
+      let ( ++ ) = Mtime.Span.add in
       Ipq.add queue
         {
           Ipq.ev= {func= newfunc; ty; name}
-        ; Ipq.time= Mtime_clock.now () ++ start_span
+        ; Ipq.time= Mtime_clock.elapsed () ++ start_span
         }
   ) ;
   if signal then Delay.signal delay
@@ -90,8 +82,8 @@ let loop () =
       (* Doesn't happen often - the queue isn't usually empty *)
       else
         let next = with_lock lock (fun () -> Ipq.maximum queue) in
-        let now = Mtime_clock.now () in
-        if Mtime.is_earlier next.Ipq.time ~than:now then (
+        let now = Mtime_clock.elapsed () in
+        if Mtime.Span.is_shorter next.Ipq.time ~than:now then (
           let todo =
             (with_lock lock (fun () -> Ipq.pop_maximum queue)).Ipq.ev
           in
@@ -103,7 +95,7 @@ let loop () =
               add_to_queue ~signal:false todo.name todo.ty timer todo.func
         ) else (* Sleep until next event. *)
           let sleep =
-            Mtime.(span next.Ipq.time now)
+            Mtime.(Span.abs_diff next.Ipq.time now)
             |> Mtime.Span.add Mtime.Span.(1 * ms)
             |> Scheduler.span_to_s
           in