Only update litestream_seq if size is below WAL header size

db.go

@@ -629,7 +629,7 @@ func (db *DB) acquireReadLock() error {
 	}
 
 	// Execute read query to obtain read lock.
-	if _, err := tx.ExecContext(db.ctx, `SELECT COUNT(1) FROM _litestream_seq;`); err != nil {
+	if _, err := tx.ExecContext(context.Background(), `SELECT COUNT(1) FROM _litestream_seq;`); err != nil {
 		_ = tx.Rollback()
 		return err
 	}
@@ -649,6 +649,10 @@ func (db *DB) releaseReadLock() error {
 	// Rollback & clear read transaction.
 	err := db.rtx.Rollback()
 	db.rtx = nil
+
+	if errors.Is(err, context.Canceled) {
+		err = nil
+	}
 	return err
 }
 
@@ -693,7 +697,7 @@ func (db *DB) createGeneration() (string, error) {
 
 	// Atomically write generation name as current generation.
 	generationNamePath := db.GenerationNamePath()
-	mode := os.FileMode(0600)
+	mode := os.FileMode(0o600)
 	if db.fileInfo != nil {
 		mode = db.fileInfo.Mode()
 	}
@@ -986,7 +990,7 @@ func (db *DB) initShadowWALFile(filename string) (int64, error) {
 	}
 
 	// Write header to new WAL shadow file.
-	mode := os.FileMode(0600)
+	mode := os.FileMode(0o600)
 	if fi := db.fileInfo; fi != nil {
 		mode = fi.Mode()
 	}
@@ -1022,7 +1026,7 @@ func (db *DB) copyToShadowWAL(filename string) (origWalSize int64, newSize int64
 	}
 	origWalSize = frameAlign(fi.Size(), db.pageSize)
 
-	w, err := os.OpenFile(filename, os.O_RDWR, 0666)
+	w, err := os.OpenFile(filename, os.O_RDWR, 0o666)
 	if err != nil {
 		return 0, 0, err
 	}
@@ -1337,7 +1341,7 @@ func (db *DB) checkpoint(ctx context.Context, generation, mode string) error {
 	// a new page is written.
 	if err := db.execCheckpoint(mode); err != nil {
 		return err
-	} else if _, err = db.db.Exec(`INSERT INTO _litestream_seq (id, seq) VALUES (1, 1) ON CONFLICT (id) DO UPDATE SET seq = seq + 1`); err != nil {
+	} else if err := db.ensureWALExists(); err != nil {
 		return err
 	}
 
@@ -1427,7 +1431,7 @@ func (db *DB) execCheckpoint(mode string) (err error) {
 
 	// Reacquire the read lock immediately after the checkpoint.
 	if err := db.acquireReadLock(); err != nil {
-		return fmt.Errorf("release read lock: %w", err)
+		return fmt.Errorf("acquire read lock: %w", err)
 	}
 
 	return nil

db_test.go

@@ -375,7 +375,7 @@ func TestDB_Sync(t *testing.T) {
 		shadowWALPath := db.ShadowWALPath(pos0.Generation, pos0.Index)
 		if buf, err := os.ReadFile(shadowWALPath); err != nil {
 			t.Fatal(err)
-		} else if err := os.WriteFile(shadowWALPath, append(buf[:litestream.WALHeaderSize-8], 0, 0, 0, 0, 0, 0, 0, 0), 0600); err != nil {
+		} else if err := os.WriteFile(shadowWALPath, append(buf[:litestream.WALHeaderSize-8], 0, 0, 0, 0, 0, 0, 0, 0), 0o600); err != nil {
 			t.Fatal(err)
 		}
 
@@ -552,12 +552,7 @@ func TestDB_Sync(t *testing.T) {
 			t.Fatal(err)
 		}
 
-		// Ensure position is now on the second index.
-		if pos, err := db.Pos(); err != nil {
-			t.Fatal(err)
-		} else if got, want := pos.Index, 1; got != want {
-			t.Fatalf("Index=%v, want %v", got, want)
-		}
+		// NOTE: The minimum checkpoint may only do a PASSIVE checkpoint so we can't guarantee a rollover.
 	})
 
 	// Ensure DB checkpoints after interval.
@@ -581,13 +576,6 @@ func TestDB_Sync(t *testing.T) {
 		} else if err := db.Sync(context.Background()); err != nil {
 			t.Fatal(err)
 		}
-
-		// Ensure position is now on the second index.
-		if pos, err := db.Pos(); err != nil {
-			t.Fatal(err)
-		} else if got, want := pos.Index, 1; got != want {
-			t.Fatalf("Index=%v, want %v", got, want)
-		}
 	})
 }
 

replica_test.go

@@ -50,6 +50,10 @@ func TestReplica_Sync(t *testing.T) {
 		t.Fatal(err)
 	}
 
+	if err := db.Checkpoint(context.Background(), litestream.CheckpointModeTruncate); err != nil {
+		t.Fatal(err)
+	}
+
 	c := file.NewReplicaClient(t.TempDir())
 	r := litestream.NewReplica(db, "")
 	c.Replica, r.Client = r, c
@@ -142,7 +146,7 @@ func TestReplica_Snapshot(t *testing.T) {
 		t.Fatal(err)
 	} else if info, err := r.Snapshot(context.Background()); err != nil {
 		t.Fatal(err)
-	} else if got, want := info.Pos(), nextIndex(pos0); got != want {
+	} else if got, want := info.Pos(), pos0.Truncate(); got != want {
 		t.Fatalf("pos=%s, want %s", got, want)
 	}
 
@@ -166,20 +170,18 @@ func TestReplica_Snapshot(t *testing.T) {
 		t.Fatal(err)
 	} else if info, err := r.Snapshot(context.Background()); err != nil {
 		t.Fatal(err)
-	} else if got, want := info.Pos(), nextIndex(pos1); got != want {
+	} else if got, want := info.Pos(), pos1.Truncate(); got != want {
 		t.Fatalf("pos=%v, want %v", got, want)
 	}
 
-	// Verify three snapshots exist.
+	// Verify snapshots exist.
 	if infos, err := r.Snapshots(context.Background()); err != nil {
 		t.Fatal(err)
-	} else if got, want := len(infos), 3; got != want {
+	} else if got, want := len(infos), 2; got != want {
 		t.Fatalf("len=%v, want %v", got, want)
 	} else if got, want := infos[0].Pos(), pos0.Truncate(); got != want {
 		t.Fatalf("info[0]=%s, want %s", got, want)
-	} else if got, want := infos[1].Pos(), nextIndex(pos0); got != want {
+	} else if got, want := infos[1].Pos(), pos1.Truncate(); got != want {
 		t.Fatalf("info[1]=%s, want %s", got, want)
-	} else if got, want := infos[2].Pos(), nextIndex(pos1); got != want {
-		t.Fatalf("info[2]=%s, want %s", got, want)
 	}
 }