unified-storage: save previous_resource_version as microsecond timestamp in compat mode (#116179)

* unified-storage: save `previous_resource_version` as microsecond timestamp in compat mode

* debug test

* fix test

* fix typo

* Fix misleading var name.

`ms` is typically the abbreviation for millisecond, not microsecond.

pkg/storage/unified/resource/datastore.go

@@ -14,6 +14,7 @@ import (
 	"github.com/grafana/grafana/pkg/apimachinery/validation"
 	"github.com/grafana/grafana/pkg/storage/unified/sql/db"
 	"github.com/grafana/grafana/pkg/storage/unified/sql/dbutil"
+	"github.com/grafana/grafana/pkg/storage/unified/sql/rvmanager"
 	"github.com/grafana/grafana/pkg/storage/unified/sql/sqltemplate"
 	gocache "github.com/patrickmn/go-cache"
 )
@@ -868,10 +869,18 @@ func (d *dataStore) applyBackwardsCompatibleChanges(ctx context.Context, tx db.T
 	if key.Action == DataActionDeleted {
 		generation = 0
 	}
+
+	// In compatibility mode, the previous RV, when available, is saved as a microsecond
+	// timestamp, as is done in the SQL backend.
+	previousRV := event.PreviousRV
+	if event.PreviousRV > 0 && isSnowflake(event.PreviousRV) {
+		previousRV = rvmanager.RVFromSnowflake(event.PreviousRV)
+	}
+
 	_, err := dbutil.Exec(ctx, tx, sqlKVUpdateLegacyResourceHistory, sqlKVLegacyUpdateHistoryRequest{
 		SQLTemplate: sqltemplate.New(kv.dialect),
 		GUID:        key.GUID,
-		PreviousRV:  event.PreviousRV,
+		PreviousRV:  previousRV,
 		Generation:  generation,
 	})
 
@@ -900,7 +909,7 @@ func (d *dataStore) applyBackwardsCompatibleChanges(ctx context.Context, tx db.T
 			Name:        key.Name,
 			Action:      action,
 			Folder:      key.Folder,
-			PreviousRV:  event.PreviousRV,
+			PreviousRV:  previousRV,
 		})
 
 		if err != nil {
@@ -916,7 +925,7 @@ func (d *dataStore) applyBackwardsCompatibleChanges(ctx context.Context, tx db.T
 			Name:        key.Name,
 			Action:      action,
 			Folder:      key.Folder,
-			PreviousRV:  event.PreviousRV,
+			PreviousRV:  previousRV,
 		})
 
 		if err != nil {
@@ -938,3 +947,15 @@ func (d *dataStore) applyBackwardsCompatibleChanges(ctx context.Context, tx db.T
 
 	return nil
 }
+
+// isSnowflake returns whether the argument passed is a snowflake ID (new) or a microsecond timestamp (old).
+// We try to interpret the number as a microsecond timestamp first. If it represents a time in the past,
+// it is considered a microsecond timestamp. Snowflake IDs are much larger integers and would lead
+// to dates in the future if interpreted as a microsecond timestamp.
+func isSnowflake(rv int64) bool {
+	ts := time.UnixMicro(rv)
+	oneHourFromNow := time.Now().Add(time.Hour)
+	isMicroSecRV := ts.Before(oneHourFromNow)
+
+	return !isMicroSecRV
+}

pkg/storage/unified/resource/notifier_test.go

@@ -456,33 +456,27 @@ func testNotifierWatchMultipleEvents(t *testing.T, ctx context.Context, notifier
 		},
 	}
 
+	errCh := make(chan error)
 	go func() {
 		for _, event := range testEvents {
-			err := eventStore.Save(ctx, event)
-			require.NoError(t, err)
+			errCh <- eventStore.Save(ctx, event)
 		}
 	}()
 
 	// Receive events
-	receivedEvents := make([]Event, 0, len(testEvents))
-	for i := 0; i < len(testEvents); i++ {
+	receivedEvents := make([]string, 0, len(testEvents))
+	for len(receivedEvents) != len(testEvents) {
 		select {
 		case event := <-events:
-			receivedEvents = append(receivedEvents, event)
+			receivedEvents = append(receivedEvents, event.Name)
+		case err := <-errCh:
+			require.NoError(t, err)
 		case <-time.After(1 * time.Second):
-			t.Fatalf("Timed out waiting for event %d", i+1)
+			t.Fatalf("Timed out waiting for event %d", len(receivedEvents)+1)
 		}
 	}
 
-	// Verify all events were received
-	assert.Len(t, receivedEvents, len(testEvents))
-
 	// Verify the events match and ordered by resource version
-	receivedNames := make([]string, len(receivedEvents))
-	for i, event := range receivedEvents {
-		receivedNames[i] = event.Name
-	}
-
 	expectedNames := []string{"test-resource-1", "test-resource-2", "test-resource-3"}
-	assert.ElementsMatch(t, expectedNames, receivedNames)
+	assert.ElementsMatch(t, expectedNames, receivedEvents)
 }

pkg/storage/unified/resource/sqlkv.go

@@ -473,8 +473,6 @@ func (k *sqlKV) Delete(ctx context.Context, section string, key string) error {
 		return ErrNotFound
 	}
 
-	// TODO reflect change to resource table
-
 	return nil
 }
 

pkg/storage/unified/resource/storage_backend.go

@@ -347,7 +347,7 @@ func (k *kvStorageBackend) WriteEvent(ctx context.Context, event WriteEvent) (in
 			return 0, fmt.Errorf("failed to write data: %w", err)
 		}
 
-		rv = rvmanager.SnowflakeFromRv(rv)
+		rv = rvmanager.SnowflakeFromRV(rv)
 		dataKey.ResourceVersion = rv
 	} else {
 		err := k.dataStore.Save(ctx, dataKey, bytes.NewReader(event.Value))