informers: don't treat relist same as sync

Background:

Before this change, DeltaFIFO emits the Sync DeltaType on Resync() and
Replace(). Seperately, the SharedInformer will only pass that event
on to handlers that have a ResyncInterval and are due for Resync. This
can cause updates to be lost if an object changes as part of the Replace(),
as it may be incorrectly discarded if the handler does not want a Resync.

What this change does:

Creates a new DeltaType, Replaced, which is emitted by DeltaFIFO on
Replace(). For backwards compatability concerns, the old behavior of
always emitting Sync is preserved unless explicity overridden.

As a result, if an object changes (or is added) on Replace(), now all
SharedInformer handlers will get a correct Add() or Update()
notification.

One additional side-effect is that handlers which do not ever want
Resyncs will now see them for all objects that have not changed during
the Replace.

Kubernetes-commit: ca1eeb99b530a6d76b464dad545abc18d4508c49

tools/cache/delta_fifo_test.go

@@ -288,6 +288,24 @@ func TestDeltaFIFO_ResyncNonExisting(t *testing.T) {
 	}
 }
 
+func TestDeltaFIFO_Resync(t *testing.T) {
+	f := NewDeltaFIFO(
+		testFifoObjectKeyFunc,
+		literalListerGetter(func() []testFifoObject {
+			return []testFifoObject{mkFifoObj("foo", 5)}
+		}),
+	)
+	f.Resync()
+
+	deltas := f.items["foo"]
+	if len(deltas) != 1 {
+		t.Fatalf("unexpected deltas length: %v", deltas)
+	}
+	if deltas[0].Type != Sync {
+		t.Errorf("unexpected delta: %v", deltas[0])
+	}
+}
+
 func TestDeltaFIFO_DeleteExistingNonPropagated(t *testing.T) {
 	f := NewDeltaFIFO(
 		testFifoObjectKeyFunc,
@@ -384,6 +402,60 @@ func TestDeltaFIFO_ReplaceMakesDeletions(t *testing.T) {
 	}
 }
 
+// TestDeltaFIFO_ReplaceMakesDeletionsReplaced is the same as the above test, but
+// ensures that a Replaced DeltaType is emitted.
+func TestDeltaFIFO_ReplaceMakesDeletionsReplaced(t *testing.T) {
+	f := NewDeltaFIFOWithOptions(DeltaFIFOOptions{
+		KeyFunction: testFifoObjectKeyFunc,
+		KnownObjects: literalListerGetter(func() []testFifoObject {
+			return []testFifoObject{mkFifoObj("foo", 5), mkFifoObj("bar", 6), mkFifoObj("baz", 7)}
+		}),
+		EmitDeltaTypeReplaced: true,
+	})
+
+	f.Delete(mkFifoObj("baz", 10))
+	f.Replace([]interface{}{mkFifoObj("foo", 6)}, "0")
+
+	expectedList := []Deltas{
+		{{Deleted, mkFifoObj("baz", 10)}},
+		{{Replaced, mkFifoObj("foo", 6)}},
+		// Since "bar" didn't have a delete event and wasn't in the Replace list
+		// it should get a tombstone key with the right Obj.
+		{{Deleted, DeletedFinalStateUnknown{Key: "bar", Obj: mkFifoObj("bar", 6)}}},
+	}
+
+	for _, expected := range expectedList {
+		cur := Pop(f).(Deltas)
+		if e, a := expected, cur; !reflect.DeepEqual(e, a) {
+			t.Errorf("Expected %#v, got %#v", e, a)
+		}
+	}
+}
+
+// TestDeltaFIFO_ReplaceDeltaType checks that passing EmitDeltaTypeReplaced
+// means that Replaced is correctly emitted.
+func TestDeltaFIFO_ReplaceDeltaType(t *testing.T) {
+	f := NewDeltaFIFOWithOptions(DeltaFIFOOptions{
+		KeyFunction: testFifoObjectKeyFunc,
+		KnownObjects: literalListerGetter(func() []testFifoObject {
+			return []testFifoObject{mkFifoObj("foo", 5)}
+		}),
+		EmitDeltaTypeReplaced: true,
+	})
+	f.Replace([]interface{}{mkFifoObj("foo", 5)}, "0")
+
+	expectedList := []Deltas{
+		{{Replaced, mkFifoObj("foo", 5)}},
+	}
+
+	for _, expected := range expectedList {
+		cur := Pop(f).(Deltas)
+		if e, a := expected, cur; !reflect.DeepEqual(e, a) {
+			t.Errorf("Expected %#v, got %#v", e, a)
+		}
+	}
+}
+
 func TestDeltaFIFO_UpdateResyncRace(t *testing.T) {
 	f := NewDeltaFIFO(
 		testFifoObjectKeyFunc,