kataras/iris · critical

err

Error message

err

What it means

middleware/rewrite.Load loads a rewrite engine from a YAML file and panics on any parser/option error, because it returns only a router wrapper and has no error return. Any invalid rewrite syntax, unreadable file, or schema violation in the YAML surfaces as this generic wrapped error at startup. It is a fail-fast design: the app cannot serve traffic without a valid rewrite table.

Source

Thrown at middleware/rewrite/rewrite.go:90

	redirects []*redirectMatch
	options   Options

	logger          *golog.Logger
	domainValidator func(string) bool
}

// Load decodes the "filename" options
// and returns a new Rewrite Engine Router Wrapper.
// It panics on errors.
// Usage:
// redirects := Load("redirects.yml")
// app.WrapRouter(redirects)
// See `New` too.
func Load(filename string) router.WrapperFunc {
	opts := LoadOptions(filename)
	engine, err := New(opts)
	if err != nil {
		panic(err)
	}
	return engine.Rewrite
}

// New returns a new Rewrite Engine based on "opts".
// It reports any parser error.
// See its `Handler` or `Rewrite` methods. Depending
// on the needs, select one.
func New(opts Options) (*Engine, error) {
	redirects := make([]*redirectMatch, 0, len(opts.RedirectMatch))

	for _, line := range opts.RedirectMatch {
		r, err := parseRedirectMatchLine(line)
		if err != nil {
			return nil, err
		}
		redirects = append(redirects, r)
	}

View on GitHub (pinned to 7bedaf55a0)

Solutions

1. Check the panic text for the parser message and fix the offending line in the rewrite YAML file.
2. Verify the file path passed to Load is correct and the file exists/is readable at runtime.
3. Prefer building with rewrite.New(rewrite.LoadOptions{...}) which returns an error you can handle instead of Load's panic.
4. Add a config-load step at boot that validates the YAML (yaml.Unmarshal into the expected struct) before calling Load.

Example fix

// before
app.WrapRouter(rewrite.Load("redirects.yml")) // panics on parse error
// after
opts := rewrite.LoadOptions{"redirects.yml"}
engine, err := rewrite.New(opts)
if err != nil {
	log.Fatalf("invalid rewrite config: %v", err)
}
app.WrapRouter(engine.Rewrite)

data, err := os.ReadFile("redirects.yml")
if err != nil { log.Fatalf("rewrite config missing: %v", err) }
var check map[string]any
if err := yaml.Unmarshal(data, &check); err != nil { log.Fatalf("invalid rewrite YAML: %v", err) }

defer func() {
	if r := recover(); r != nil {
		log.Fatalf("rewrite.Load failed: %v", r)
	}
}()

When it happens

Trigger: Calling rewrite.Load("redirects.yml") with a file that does not exist, is not valid YAML, or whose keys/values do not match the expected rewrite schema (e.g. a source pattern with invalid syntax).

Common situations: Typos in the redirects file path, manually edited redirect rules with bad regex/anchors, CI deploying an empty or corrupted config file, or a schema change after upgrading iris.

Related errors

• panic(err)
• err
• iris: switch: hosts: invalid target type: %T
• panic(err)
• default configuration file '" + filename + "' does not exist

AI-assisted analysis of kataras/iris@7bedaf55a0 (2026-08-30). Data as JSON: /api/errors/9a69b4f424219a3d. Report an issue: GitHub.