reconciler: Prune after initialized even with empty table

Pruning should be performed when the table has initialized even
when the table is empty. Use a 1 second ticker time until table
has initialized and pruned and then switch to normal prune interval.

Signed-off-by: Jussi Maki <[email protected]>

reconciler/reconciler.go

@@ -28,9 +28,18 @@ func (r *reconciler[Obj]) Prune() {
 }
 
 func (r *reconciler[Obj]) reconcileLoop(ctx context.Context, health cell.Health) error {
-	var pruneTickerChan <-chan time.Time
+	var (
+		pruneTickerChan <-chan time.Time
+		pruneTicker     *time.Ticker
+	)
+
+	// If pruning is enabled, start a ticker to initiate the pruning
+	// Since we want to prune soon after the table has initialized even when it is empty,
+	// use a 1 second ticker until we've done the initial pruning after which we switch to
+	// the configured prune interval.
+
 	if r.config.PruneInterval > 0 {
-		pruneTicker := time.NewTicker(r.config.PruneInterval)
+		pruneTicker = time.NewTicker(time.Second)
 		defer pruneTicker.Stop()
 		pruneTickerChan = pruneTicker.C
 	}
@@ -55,15 +64,17 @@ func (r *reconciler[Obj]) reconcileLoop(ctx context.Context, health cell.Health)
 			return err
 		}
 		prune := false
+		retries := false
+		tableChanged := false
 
 		// Wait for trigger
 		select {
 		case <-ctx.Done():
 			return ctx.Err()
 		case <-r.retries.Wait():
-			// Object(s) are ready to be retried
+			retries = true
 		case <-tableWatchChan:
-			// Table has changed
+			tableChanged = true
 		case <-pruneTickerChan:
 			prune = true
 		case <-r.externalPruneTrigger:
@@ -77,7 +88,10 @@ func (r *reconciler[Obj]) reconcileLoop(ctx context.Context, health cell.Health)
 
 		// Perform incremental reconciliation and retries of previously failed
 		// objects.
-		errs := r.incremental(ctx, txn, changes)
+		var errs []error
+		if retries || tableChanged {
+			errs = r.incremental(ctx, txn, changes)
+		}
 
 		if !tableInitialized {
 			if r.config.Table.Initialized(txn) {
@@ -86,6 +100,12 @@ func (r *reconciler[Obj]) reconcileLoop(ctx context.Context, health cell.Health)
 				// Do an immediate pruning now as the table has finished
 				// initializing and pruning is enabled.
 				prune = r.config.PruneInterval != 0
+
+				// Reconfigure the ticker to do the next pruning with the
+				// configured interval.
+				if r.config.PruneInterval > 0 {
+					pruneTicker.Reset(r.config.PruneInterval)
+				}
 			} else {
 				// Table not initialized yet, skip this pruning round.
 				prune = false

reconciler/reconciler_test.go

@@ -241,16 +241,14 @@ func testReconciler(t *testing.T, batchOps bool) {
 		h.triggerPrune()
 		h.expectOp(opUpdate(ID_1))
 		h.expectHealth(cell.StatusOK, "OK, 1 object(s)", "")
-		h.markInitialized()
-
-		// After initialization we expect to see pruning immediately
-		// as soon as something changes. Marking the table initialized
-		// does not yet trigger the reconciler since it's waiting for
-		// objects to change.
 		h.insert(ID_2, NonFaulty, reconciler.StatusPending())
-		h.expectOps(opUpdate(ID_2), opPrune(2))
+		h.expectOp(opUpdate(ID_2))
 		h.expectHealth(cell.StatusOK, "OK, 2 object(s)", "")
 
+		// After initialization we expect to see pruning immediately.
+		h.markInitialized()
+		h.expectOps(opPrune(2))
+
 		// Pruning can be now triggered at will.
 		h.triggerPrune()
 		h.expectOps(opUpdate(ID_2), opPrune(2), opPrune(2))
@@ -304,6 +302,19 @@ func testReconciler(t *testing.T, batchOps bool) {
 		assert.Equal(t, getInt(h.m.PruneCurrentErrorsVar.Get("test")), int64(0), "PruneCurrentErrors")
 	})
 
+	runTest("pruning-empty-table",
+		[]reconciler.Option{
+			reconciler.WithPruning(100 * time.Millisecond),
+		},
+		func(h testHelper) {
+			// Mark the table initialized. This should trigger the pruning
+			// even when there are no objects.
+			h.markInitialized()
+
+			// Expect to see the initial pruning and then periodic pruning.
+			h.expectOps(opPrune(0), opPrune(0))
+		})
+
 	runTest("refreshing",
 		[]reconciler.Option{
 			reconciler.WithPruning(0), // Disable