Add support for PERSIST journal mode

.github/workflows/push.yml

@@ -32,7 +32,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        journal_mode: [delete, wal]
+        journal_mode: [delete, persist, wal]
     steps:
       - uses: actions/checkout@v3
 
@@ -66,7 +66,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        journal_mode: [delete, wal]
+        journal_mode: [delete, persist, wal]
     steps:
       - uses: actions/checkout@v3
 

cmd/litefs/main_test.go

@@ -144,14 +144,21 @@ func TestSingleNode_DatabaseChecksumMismatch(t *testing.T) {
 		t.Fatal(err)
 	}
 
-	if testingutil.IsWALMode() {
-		if err := m0.Run(context.Background()); err == nil || err.Error() != `cannot open store: open databases: open database("db"): verify database file: database checksum (a9e884061ea4e488) does not match latest LTX checksum (fa337f5ece449f39)` {
+	switch mode := testingutil.JournalMode(); mode {
+	case "delete":
+		if err := m0.Run(context.Background()); err == nil || err.Error() != `cannot open store: open databases: open database("db"): verify database file: database checksum (9d81a60d39fb4760) does not match latest LTX checksum (ce5a5d55e91b3cd1)` {
 			t.Fatalf("unexpected error: %s", err)
 		}
-	} else {
-		if err := m0.Run(context.Background()); err == nil || err.Error() != `cannot open store: open databases: open database("db"): verify database file: database checksum (9d81a60d39fb4760) does not match latest LTX checksum (ce5a5d55e91b3cd1)` {
+	case "persist":
+		if err := m0.Run(context.Background()); err == nil || err.Error() != `cannot open store: open databases: open database("db"): verify database file: database checksum (ff2d4d6d60fd80cd) does not match latest LTX checksum (ce5a5d55e91b3cd1)` {
+			t.Fatalf("unexpected error: %s", err)
+		}
+	case "wal":
+		if err := m0.Run(context.Background()); err == nil || err.Error() != `cannot open store: open databases: open database("db"): verify database file: database checksum (a9e884061ea4e488) does not match latest LTX checksum (fa337f5ece449f39)` {
 			t.Fatalf("unexpected error: %s", err)
 		}
+	default:
+		t.Fatalf("invalid journal mode: %q", mode)
 	}
 }
 

db.go

@@ -815,11 +815,29 @@ func (db *DB) WriteJournal(f *os.File, data []byte, offset int64) error {
 	if !db.store.IsPrimary() {
 		return ErrReadOnlyReplica
 	}
+
+	// Assume this is a PERSIST commit if the initial header bytes are cleared.
+	if offset == 0 && len(data) == SQLITE_DATABASE_SIZE_OFFSET && isByteSliceZero(data) {
+		if err := db.CommitJournal(JournalModePersist); err != nil {
+			return fmt.Errorf("commit journal (PERSIST): %w", err)
+		}
+	}
+
 	_, err := f.WriteAt(data, offset)
 	dbJournalWriteCountMetricVec.WithLabelValues(db.name).Inc()
 	return err
 }
 
+// isByteSliceZero returns true if b only contains NULL bytes.
+func isByteSliceZero(b []byte) bool {
+	for _, v := range b {
+		if v != 0 {
+			return false
+		}
+	}
+	return true
+}
+
 // CommitJournal deletes the journal file which commits or rolls back the transaction.
 func (db *DB) CommitJournal(mode JournalMode) error {
 	db.mu.Lock()
@@ -1050,7 +1068,19 @@ func (db *DB) invalidateJournal(mode JournalMode) error {
 		}
 
 	case JournalModePersist:
-		return fmt.Errorf("journal mode not implemented: PERSIST")
+		f, err := os.OpenFile(db.JournalPath(), os.O_RDWR, 0666)
+		if err != nil && !os.IsNotExist(err) {
+			return fmt.Errorf("open journal: %w", err)
+		}
+		defer func() { _ = f.Close() }()
+
+		if _, err := f.Write(make([]byte, SQLITE_JOURNAL_HEADER_SIZE)); err != nil {
+			return fmt.Errorf("clear journal header: %w", err)
+		} else if err := f.Sync(); err != nil {
+			return fmt.Errorf("sync journal: %w", err)
+		} else if err := f.Close(); err != nil {
+			return fmt.Errorf("close journal: %w", err)
+		}
 
 	default:
 		return fmt.Errorf("invalid journal: %q", mode)
@@ -1604,12 +1634,15 @@ func TrimName(name string) string {
 const (
 	SQLITE_DATABASE_HEADER_STRING = "SQLite format 3\x00"
 
+	// Location of the database size, in pages, in the main database file.
+	SQLITE_DATABASE_SIZE_OFFSET = 28
+
 	/// Magic header string that identifies a SQLite journal header.
 	/// https://www.sqlite.org/fileformat.html#the_rollback_journal
 	SQLITE_JOURNAL_HEADER_STRING = "\xd9\xd5\x05\xf9\x20\xa1\x63\xd7"
 
-	// Location of the database size, in pages, in the main database file.
-	SQLITE_DATABASE_SIZE_OFFSET = 28
+	// Size of the journal header, in bytes.
+	SQLITE_JOURNAL_HEADER_SIZE = 28
 )
 
 // LockType represents a SQLite lock type.

fuse/file_system_test.go

@@ -253,10 +253,6 @@ func TestFileSystem_MultipleJournalSegments(t *testing.T) {
 }
 
 func TestFileSystem_ReadOnly(t *testing.T) {
-	if testingutil.IsWALMode() {
-		t.Skip("SQLITE_READONLY not yet supported in WAL mode")
-	}
-
 	dir := t.TempDir()
 	fs := newOpenFileSystem(t, dir, litefs.NewStaticLeaser(true, "localhost", "http://localhost:20202"))
 	dsn := filepath.Join(fs.Path(), "db")
@@ -280,10 +276,26 @@ func TestFileSystem_ReadOnly(t *testing.T) {
 
 	// Attempt to write to read-only database.
 	db = testingutil.OpenSQLDB(t, dsn)
-	var e sqlite3.Error
-	if _, err := db.Exec(`INSERT INTO t VALUES (100)`); !errors.As(err, &e) || e.Code != sqlite3.ErrReadonly {
-		t.Fatalf("unexpected error: %s", err)
+	_, err := db.Exec(`INSERT INTO t VALUES (100)`)
+
+	switch mode := testingutil.JournalMode(); mode {
+	case "delete":
+		var e sqlite3.Error
+		if !errors.As(err, &e) || e.Code != sqlite3.ErrReadonly {
+			t.Fatalf("unexpected error: %s", err)
+		}
+	case "persist":
+		if err == nil || err.Error() != `disk I/O error: permission denied` {
+			t.Fatalf("unexpected error: %s", err)
+		}
+	case "wal":
+		if err == nil || err.Error() != `disk I/O error` {
+			t.Fatalf("unexpected error: %s", err)
+		}
+	default:
+		t.Fatalf("invalid journal mode: %q", mode)
 	}
+
 	if err := db.Close(); err != nil {
 		t.Fatal(err)
 	}

fuse/journal_node.go

@@ -136,7 +136,7 @@ func (h *JournalHandle) Read(ctx context.Context, req *fuse.ReadRequest, resp *f
 func (h *JournalHandle) Write(ctx context.Context, req *fuse.WriteRequest, resp *fuse.WriteResponse) error {
 	if err := h.node.db.WriteJournal(h.file, req.Data, req.Offset); err != nil {
 		log.Printf("fuse: write(): journal error: %s", err)
-		return err
+		return ToError(err)
 	}
 	resp.Size = len(req.Data)
 	return nil