feat(db): 控制面 PG 定时备份、迁移前快照与原子恢复

cmd/felis/migrate.go

@@ -7,15 +7,24 @@ import (
 	"io"
 
 	"felis.lolicon.best/internal/config"
+	"felis.lolicon.best/internal/dbbackup"
 	"felis.lolicon.best/internal/store"
 )
 
 // cmdMigrate implements `felis migrate up`: load config, open the database, and
 // apply every pending embedded migration under the advisory lock (spec §6).
+//
+// Migrations only roll forward, and some drop data (0017_drop_password), so a
+// database that already holds a schema and has migrations pending is bundled
+// first (internal/dbbackup, label pre-migrate). A failed snapshot stops the
+// upgrade; -no-backup is the explicit way past it, e.g. for an external
+// database whose server is newer than the host's pg_dump.
 func cmdMigrate(args []string, stdout, stderr io.Writer) int {
 	fs := flag.NewFlagSet("migrate", flag.ContinueOnError)
 	fs.SetOutput(stderr)
 	cfgPath := fs.String("config", "/etc/felis/felis.toml", "path to felis.toml")
+	backupDir := fs.String("backup-dir", dbbackup.DefaultDir, "where the pre-migration snapshot goes")
+	noBackup := fs.Bool("no-backup", false, "apply pending migrations without snapshotting the database first")
 	// The "up" verb precedes any flags (felis migrate up -config path). Go's
 	// flag.Parse stops at the first non-flag token and would never see a flag
 	// placed after "up", silently falling back to the default -config. Pull the
@@ -48,6 +57,18 @@ func cmdMigrate(args []string, stdout, stderr io.Writer) int {
 		return 1
 	}
 
+	if !*noBackup {
+		path, err := preMigrateBackup(ctx, drv, migrations, cfg.Database.URL, *backupDir, stderr)
+		if err != nil {
+			fmt.Fprintf(stderr, "felis migrate: pre-migration backup failed, nothing applied: %v\n", err)
+			fmt.Fprintln(stderr, "  fix the backup, or re-run with -no-backup to migrate without one")
+			return 1
+		}
+		if path != "" {
+			fmt.Fprintf(stdout, "felis migrate: database snapshot %s\n", path)
+		}
+	}
+
 	applied, err := store.Up(ctx, drv, migrations)
 	if err != nil {
 		fmt.Fprintf(stderr, "felis migrate: %v\n", err)
@@ -60,3 +81,33 @@ func cmdMigrate(args []string, stdout, stderr io.Writer) int {
 	}
 	return 0
 }
+
+// preMigrateBackup bundles the database when it already carries a schema and
+// some of migrations are not applied yet, and returns the bundle's path ("" when
+// there was nothing to protect: a fresh database, or nothing pending).
+func preMigrateBackup(ctx context.Context, drv store.Driver, migrations []store.Migration, dbURL, dir string, log io.Writer) (string, error) {
+	if err := drv.EnsureVersionTable(ctx); err != nil {
+		return "", fmt.Errorf("ensure version table: %w", err)
+	}
+	done, err := drv.AppliedVersions(ctx)
+	if err != nil {
+		return "", fmt.Errorf("read applied versions: %w", err)
+	}
+	if len(done) == 0 || !hasPending(done, migrations) {
+		return "", nil
+	}
+	return dbbackup.Backup(ctx, dbbackup.BackupOptions{
+		DatabaseURL: dbURL, Dir: dir, Label: dbbackup.LabelPreMigrate,
+		Keep: defaultKeep[dbbackup.LabelPreMigrate], StateDir: dbbackup.DefaultStateDir,
+		Version: resolvedVersion(), Log: log, Record: true,
+	})
+}
+
+func hasPending(done map[int]struct{}, migrations []store.Migration) bool {
+	for _, m := range migrations {
+		if _, ok := done[m.Version]; !ok {
+			return true
+		}
+	}
+	return false
+}