benbjohnson/litestream · warning

failed to format response: %w

Error message

failed to format response: %w

What it means

`litestream status -json` failed to json.MarshalIndent the collected DB status slices. Like the sibling start/stop formatter, the status types are JSON-safe structs, so this is a defensive branch that should be unreachable; it guards against future schema changes introducing unmarshalable values.

Source

Thrown at cmd/litestream/status.go:63

	for _, dbConfig := range config.DBs {
		db, err := NewDBFromConfig(dbConfig)
		if err != nil {
			return err
		}

		// Filter if path specified.
		if filterPath != "" && db.Path() != filterPath {
			continue
		}

		statuses = append(statuses, c.getDBStatus(db))
	}

	if *jsonOutput {
		output, err := json.MarshalIndent(statuses, "", "  ")
		if err != nil {
			return fmt.Errorf("failed to format response: %w", err)
		}
		fmt.Println(string(output))
		return nil
	}

	w := tabwriter.NewWriter(os.Stdout, 0, 8, 2, ' ', 0)
	defer w.Flush()

	fmt.Fprintln(w, "database\tstatus\tlocal txid\twal size")
	for _, status := range statuses {
		fmt.Fprintf(w, "%s\t%s\t%s\t%s\n",
			status.Database,
			status.Status,
			status.LocalTXID,
			status.WALSize,
		)
	}

View on GitHub (pinned to 4ed7a308f6)

Solutions

1. No user action needed with stock litestream
2. If you patched the status structs, make every field JSON-encodable (e.g. convert chan/func to strings or omit them)
3. Fall back to the tabular output (omit -json) which doesn't marshal

When it happens

Trigger: Running `litestream status -json` when one or more databases are registered and the marshaled value contains an unsupported type — not reachable with current status struct definitions.

Common situations: Only during development after adding a chan/func/cyclic field to a status struct.

Understand the failure class

Background: json.Marshal / "failed to marshal" errors in Go: why "unsupported type" happens and how to fix it — this error's family across 22 libraries.

Related errors

• failed to format response: %w
• failed to format response: %w
• failed to format response: %w
• failed to marshal request: %w
• failed to format response: %w

AI-assisted analysis of benbjohnson/litestream@4ed7a308f6 (2026-09-06). Data as JSON: /api/errors/138d94d54fd35e0f. Report an issue: GitHub.