apache/beam · error

error reconciling type

Error message

error reconciling type %v

What it means

During reconcileRegistrations, each queued type is registered into the schema registry. If registerType returns an error for a given type, this error wraps it with the offending type name. It means a queued type could not be converted into a schema.

Solutions

1. Read the wrapped cause to find the failing type and fix the specific registration problem (embedded unexported pointer, unsupported kind).
2. Register an explicit custom coder for the type so reconciliation is skipped.
3. Restructure the type to a schema-friendly shape (no embedded unexported pointers, serializable fields only).

Example fix

// before: type with embedded pointer to unexported type
type outer struct { *inner }
// after
schema.RegisterCustomTypeProvider(...) // or restructure:
type outer struct { Inner *exportedInner }

// Pre-check the type registers cleanly
if _, err := schema.ToType(reflect.TypeOf(myType{})); err != nil {
    return fmt.Errorf("type %v not schema-compatible: %w", reflect.TypeOf(myType{}), err)
}

v, err := schema.FromType(t)
if err != nil {
    if strings.Contains(err.Error(), "error reconciling type") {
        // register a custom coder fallback for this type
    }
}

When it happens

Trigger: Calling schema.Registered, schema.FromType, or schema.ToType after RegisterType queued a type whose registerType call fails (bad embedded fields, unregistered logical types, unsupported kinds).

Common situations: First actual use of a lazily-registered type in a schema operation surfaces the deferred registration failure; types with unsupported shapes (interfaces, funcs) mixed with required schema conversion.

Understand the failure class

Background: Schema validation failed / invalid input schema: payload rejected because its shape doesn't match the expected schema — this error's family across 28 libraries.

Related errors

• can't generate row coder for type
• cannot make schema for type
• decoding a *
• decoding a
• panicked

AI-assisted analysis of apache/beam@12126d8942 (2026-09-13). Data as JSON: /api/errors/e916c350f2bb4398. Report an issue: GitHub.

Appendix: source

Thrown at sdks/go/pkg/beam/core/runtime/graphx/schema/schema.go:135

	var ut reflect.Type
	defer func() {
		if r := recover(); r != nil {
			deferedErr = errors.Errorf("panicked: %v", r)
			deferedErr = errors.WithContextf(deferedErr, "reconciling schema registration for type %v", ut)
		}
	}()
	for _, ut := range r.toReconcile {
		check := func(ut reflect.Type) bool {
			return coder.LookupCustomCoder(ut) != nil
		}
		// We could have either a pointer or non pointer here,
		// so we strip pointerness and then check both.
		vT := reflectx.SkipPtr(ut)
		if check(vT) || check(reflect.PtrTo(vT)) {
			continue
		}
		if err := r.registerType(ut, map[reflect.Type]struct{}{}); err != nil {
			return errors.Wrapf(err, "error reconciling type %v", ut)
		}
	}
	r.toReconcile = nil
	return nil
}

func implements(ut, ifacet reflect.Type) bool {
	if ut.Implements(ifacet) {
		return true
	}
	switch ut.Kind() {
	case reflect.Ptr:
		t := ut.Elem()
		if t.Implements(ifacet) {
			return true
		}
		return implements(t, ifacet)
	case reflect.Struct:

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