| 1 | package topicstate |
| 2 | |
| 3 | import ( |
| 4 | "context" |
| 5 | "database/sql" |
| 6 | "fmt" |
| 7 | "net/url" |
| 8 | "os" |
| 9 | "path/filepath" |
| 10 | |
| 11 | "reasonix/internal/sqliteuri" |
| 12 | ) |
| 13 | |
| 14 | // BackupExisting reads an existing database without running schema migrations. |
| 15 | // VACUUM INTO captures a consistent SQLite snapshot including committed WAL |
| 16 | // pages and unknown tables/columns. The destination must not already exist. |
| 17 | func BackupExisting(ctx context.Context, path, destination string) error { |
| 18 | info, err := os.Lstat(path) |
| 19 | if err != nil { |
| 20 | return err |
| 21 | } |
| 22 | if !info.Mode().IsRegular() { |
| 23 | return fmt.Errorf("topic state is not a regular file") |
| 24 | } |
| 25 | if _, err := os.Lstat(destination); err == nil { |
| 26 | return &os.PathError{Op: "backup", Path: destination, Err: os.ErrExist} |
| 27 | } else if !os.IsNotExist(err) { |
| 28 | return err |
| 29 | } |
| 30 | q := url.Values{} |
| 31 | q.Set("mode", "ro") |
| 32 | q.Add("_pragma", "busy_timeout(5000)") |
| 33 | dsn, err := sqliteuri.Disk(path, q) |
| 34 | if err != nil { |
| 35 | return err |
| 36 | } |
| 37 | db, err := sql.Open("sqlite", dsn) |
| 38 | if err != nil { |
| 39 | return err |
| 40 | } |
| 41 | defer db.Close() |
| 42 | // Build the snapshot privately and publish it without replacement. VACUUM |
| 43 | // itself accepts existing empty files, and a preflight existence check alone |
| 44 | // cannot protect a destination created while the snapshot is being built. |
| 45 | parent, err := filepath.Abs(filepath.Dir(destination)) |
| 46 | if err != nil { |
| 47 | return err |
| 48 | } |
| 49 | tmp, err := os.MkdirTemp(parent, ".topic-backup-") |
| 50 | if err != nil { |
| 51 | return err |
| 52 | } |
| 53 | defer os.RemoveAll(tmp) |
| 54 | snapshot := filepath.Join(tmp, "snapshot.sqlite") |
| 55 | if _, err := db.ExecContext(ctx, "VACUUM INTO ?", snapshot); err != nil { |
| 56 | return err |
| 57 | } |
| 58 | if err := os.Chmod(snapshot, 0o600); err != nil { |
| 59 | return err |
| 60 | } |
| 61 | return os.Link(snapshot, destination) |
| 62 | } |
| 63 |