Round a merge window key's time to live up to a whole second, as the server rounds down (issue 973)

cmd/mesh-controller/merge_window_bus.go

@@ -57,11 +57,13 @@ func windowDeadlines(b inventory.Plan, now time.Time) (quiet, most time.Duration
 	if b.Delivery == nil || b.Delivery.Batch == nil || windowClosed(b, now) {
 		return 0, 0, false
 	}
+	// Rounded up to a whole second, at least one: the server rounds a key's time to live down to whole seconds, so
+	// a fraction would close the key before the record's time and the look would cut nothing.
 	least := func(d time.Duration) time.Duration {
 		if d < time.Second {
 			return time.Second
 		}
-		return d
+		return (d + time.Second - 1) / time.Second * time.Second
 	}
 	w := b.Delivery.Batch
 	return least(w.ClosesAt.Sub(now)), least(w.AtMost.Sub(now)), true

cmd/mesh-controller/merge_window_bus_test.go

@@ -136,3 +136,16 @@ func TestTheDeadlinesOfABatchsKeys(t *testing.T) {
 		}
 	}
 }
+
+// A deadline that is not a whole number of seconds is rounded up, never down: the server rounds a key's time to live
+// down to whole seconds, so 89.999999 s would expire at 89 s, before the window is closed by the record's times, and
+// the look would cut nothing (review of issue 973).
+func TestAFractionalDeadlineIsRoundedUpToTheNextWholeSecond(t *testing.T) {
+	now := time.Date(2026, 10, 17, 12, 0, 0, 0, time.UTC)
+	b := inventory.Plan{State: inventory.PlanAssembling, Delivery: &inventory.PlanDelivery{Batch: &inventory.PlanBatch{
+		ClosesAt: now.Add(89*time.Second + 999999*time.Microsecond), AtMost: now.Add(599*time.Second + time.Nanosecond)}}}
+	quiet, most, armed := windowDeadlines(b, now)
+	if !armed || quiet != 90*time.Second || most != 600*time.Second {
+		t.Errorf("deadlines %v, %v (armed %v); want 1m30s, 10m0s", quiet, most, armed)
+	}
+}