What causes "reconciling for ToType" in apache/beam?

Inspect the wrapped inner error — it names the registration that failed to reconcile

reconciling for ToType

Error message

reconciling for ToType

What it means

Wraps any failure from Registry.reconcileRegistrations() when calling the public Registry.ToType(s). Reconciliation processes pending logical-type registrations into lookup tables; if that internal step fails (duplicate URNs, malformed registered types, conversion errors), ToType cannot proceed and this wrapper is returned.

Source

Thrown at sdks/go/pkg/beam/core/runtime/graphx/schema/schema.go:692

	reflect.Int:     reflectx.Int,
	reflect.Int8:    reflectx.Int8,
	reflect.Int16:   reflectx.Int16,
	reflect.Int32:   reflectx.Int32,
	reflect.Int64:   reflectx.Int64,
	reflect.Float32: reflectx.Float32,
	reflect.Float64: reflectx.Float64,
	reflect.String:  reflectx.String,
	reflect.Bool:    reflectx.Bool,
}

var emptyStructType = reflect.TypeOf((*struct{})(nil)).Elem()

// ToType returns a Go type of the passed in Schema.
// Types returned by ToType are always of Struct kind.
// Returns an error if the Schema cannot be converted to a type.
func (r *Registry) ToType(s *pipepb.Schema) (reflect.Type, error) {
	if err := r.reconcileRegistrations(); err != nil {
		return nil, errors.Wrap(err, "reconciling for ToType")
	}
	r.rwmu.RLock()
	defer r.rwmu.RUnlock()
	return r.toType(s)
}

// toType must only be called while holding the r.rwmu lock (read or write)
func (r *Registry) toType(s *pipepb.Schema) (reflect.Type, error) {
	if t, ok := r.idToType[s.GetId()]; ok {
		return t, nil
	}
	if lID, ok := fromLogicalOption(s.GetOptions()); ok {
		if lt, ok := r.logicalTypes[lID]; ok {
			return lt.GoType(), nil
		}
	}

	fields := make([]reflect.StructField, 0, len(s.GetFields()))

View on GitHub (pinned to 12126d8942)

Solutions

Inspect the wrapped inner error — it names the registration that failed to reconcile
Verify all RegisterLogicalType calls use unique URNs and valid type providers
Ensure registered logical types' metadata schemas can themselves be converted (no unsupported kinds)
Call reconcileRegistrations-triggering APIs early (e.g. in tests) to surface registration bugs at init

Example fix

// before (duplicate URN registered twice)
schema.RegisterLogicalType(myTypeA) // urn "acme:foo"
schema.RegisterLogicalType(myTypeB) // same urn "acme:foo"
// after
schema.RegisterLogicalType(myTypeB) // use a distinct URN "acme:bar"

Defensive patterns

Strategy: try-catch

Validate before calling

func init() {
  // exercise reconciliation early
  if _, err := registry.ToType(&pipepb.Schema{}); err != nil {
    panic("logical type registration broken: " + err.Error())
  }
}

Try / catch

t, err := registry.ToType(s)
if err != nil {
  return nil, fmt.Errorf("ToType failed during registration reconcile: %w", err)
}

Prevention

Register logical types exactly once with unique URNs
Add an init-time smoke test that forces reconcileRegistrations
Avoid registering logical types whose conversion functions themselves fail schema conversion

When it happens

Trigger: Calling registry.ToType(schema) after one or more RegisterLogicalType calls where reconciliation fails — e.g. a registered logical type whose To/From functions reference types that themselves fail schema conversion, or a duplicate URN.

Common situations: Applications registering logical types at init time across multiple packages; an init-order or bad registration surfaces only later when ToType is invoked during pipeline construction or cross-language type translation.

Understand the failure class

Background: "Invalid state transition" errors: "status must be X, actually Y", "already rejected/charging/uninstalled", "cannot ... while running" — what they mean when a library rejects your call — this error's family across 31 libraries.

Related errors

AI-assisted analysis of apache/beam@12126d8942 (2026-09-13). Data as JSON: /api/errors/b8d93a44511c4ed6. Report an issue: GitHub.