Prevent the staleness of an optimized revision from exceeding the gc …

…window

internal/datastore/revisions/remoteclock.go

@@ -25,6 +25,15 @@ type RemoteClockRevisions struct {
 
 // NewRemoteClockRevisions returns a RemoteClockRevisions for the given configuration
 func NewRemoteClockRevisions(gcWindow, maxRevisionStaleness, followerReadDelay, quantization time.Duration) *RemoteClockRevisions {
+	// Ensure the max revision staleness never exceeds the GC window.
+	if maxRevisionStaleness > gcWindow {
+		log.Warn().
+			Dur("maxRevisionStaleness", maxRevisionStaleness).
+			Dur("gcWindow", gcWindow).
+			Msg("the configured maximum revision staleness exceeds the configured gc window, so capping to gcWindow")
+		maxRevisionStaleness = gcWindow - 1
+	}
+
 	revisions := &RemoteClockRevisions{
 		CachedOptimizedRevisions: NewCachedOptimizedRevisions(
 			maxRevisionStaleness,

internal/datastore/revisions/remoteclock_test.go

@@ -143,3 +143,42 @@ func TestRemoteClockCheckRevisions(t *testing.T) {
 		})
 	}
 }
+
+func TestRemoteClockStalenessBeyondGC(t *testing.T) {
+	// Set a GC window of 1 hour.
+	gcWindow := 1 * time.Hour
+
+	// Set a max revision staleness of 100 hours, well in excess of the GC window.
+	maxRevisionStaleness := 100 * time.Hour
+
+	rcr := NewRemoteClockRevisions(gcWindow, maxRevisionStaleness, 0, 0)
+
+	remoteClock := clock.NewMock()
+	rcr.clockFn = remoteClock
+	rcr.SetNowFunc(func(ctx context.Context) (datastore.Revision, error) {
+		log.Debug().Stringer("now", remoteClock.Now()).Msg("current remote time")
+		return NewForTime(remoteClock.Now()), nil
+	})
+
+	// Set the current time to 1.
+	currentTime := int64(1)
+	remoteClock.Set(time.Unix(currentTime, 0))
+
+	// Call optimized revision.
+	optimized, err := rcr.OptimizedRevision(context.Background())
+	require.NoError(t, err)
+
+	// Ensure the optimized revision is not past the GC window.
+	err = rcr.CheckRevision(context.Background(), optimized)
+	require.NoError(t, err)
+
+	// Set the current time to 100001 to ensure the optimized revision is past the GC window.
+	remoteClock.Set(time.Unix(100001, 0))
+
+	newOptimized, err := rcr.OptimizedRevision(context.Background())
+	require.NoError(t, err)
+
+	// Ensure the new optimized revision is not past the GC window.
+	err = rcr.CheckRevision(context.Background(), newOptimized)
+	require.NoError(t, err)
+}