Close a batch's merge window by the expiry of a key on the bus, heard by a watcher, and drop the five-second cutter (issue 973)

cmd/mesh-controller/batches.go

@@ -63,9 +63,6 @@ var (
 // mergeWindowFileVar names the file the controller's window settings are written to.
 const mergeWindowFileVar = "MESH_MERGE_WINDOW_FILE"
 
-// batchCutEvery is how often the controller looks whether a batch's window closed.
-const batchCutEvery = 5 * time.Second
-
 // batchLateAfter is how long past its maximum a batch may still be assembling, with no walk open, before
 // the controller is said to have failed to cut it (ADR 0276 decision 9).
 const batchLateAfter = time.Minute
@@ -595,7 +592,13 @@ func keepBatchBecause(ctx context.Context, inv *inventory.Inventory, b *inventor
 	if unNoted(*b) == before {
 		return nil
 	}
-	return inv.SavePlan(ctx, b)
+	if err := inv.SavePlan(ctx, b); err != nil {
+		return err
+	}
+	// The window's clock follows the record, only when the record moved: a merge made the quiet key again, a
+	// batch that opened made its most (ADR 0407 decision 1).
+	armWindow(ctx, *b, now)
+	return nil
 }
 
 // windowOf is when a batch's window closes, unless another merge comes, and when at the latest: the last
@@ -748,27 +751,6 @@ func nameMerges(ctx context.Context, inv *inventory.Inventory, p *inventory.Plan
 	return inv.SavePlan(ctx, p)
 }
 
-// batchCutter cuts what is due on a timer, until the context ends: a window closes with no merge to say so.
-func batchCutter(ctx context.Context, open *stores) {
-	tick := time.NewTicker(batchCutEvery)
-	defer tick.Stop()
-	for {
-		select {
-		case <-ctx.Done():
-			return
-		case <-tick.C:
-		}
-		release, err := open.inventory.HoldPlans(ctx, false)
-		if err != nil {
-			continue // whoever holds the plans moves them, and cuts at the end
-		}
-		if err := cutBatchesHeld(ctx, open, time.Now().UTC()); err != nil {
-			fmt.Printf("batches: %v\n", err)
-		}
-		release()
-	}
-}
-
 // cutBatchesHeld takes the step that is due, for a caller holding the plans: after a failed walk, the search
 // for the merge that brought the failure; with no walk open, the next merge of that search walked alone; else
 // each closed batch cut into a walk with the waiting walks it is related to folded in, unless it is related to a
@@ -904,6 +886,9 @@ func cutUnrelated(ctx context.Context, open *stores, batches, started, waiting [
 			return err
 		}
 		waiting = keep
+		if c := windowClockOf(); c != nil {
+			c.Forget(ctx, b.ID) // a batch cut has no window left to close
+		}
 		cut, err := inv.PlanByID(ctx, b.ID)
 		if err != nil {
 			return err