apache/beam · error

unable to genereate schema uuid for type

Error message

unable to genereate schema uuid for type %s: %v

What it means

After hashing the typename, getUUID seeds uuid.NewRandomFromReader with the digest to produce a deterministic UUID. If that call errors, the library panics because schema UUID generation is fundamental and cannot meaningfully continue.

Solutions

1. Retry the operation
2. Upgrade the Beam SDK / google/uuid dependency to a fixed version
3. File a bug with a reproducing stack trace if it persists

defer func() { if r := recover(); r != nil { err = fmt.Errorf("schema uuid generation failed: %v", r) } }()

When it happens

Trigger: fromType or structToSchema calling getUUID when uuid.NewRandomFromReader fails — practically only when the reader cannot supply 16 bytes, indicating an internal bug.

Common situations: Effectively unreachable in normal use; would surface as an internal invariant break during schema registration or serialization.

Understand the failure class

Background: "This is a bug, please report it": internal invariant violations, unreachable panics, and SNH errors explained — this error's family across 47 libraries.

Related errors

• unable to generate schema uuid for
• batch: failed to marshal worker UUID
• invalid logical type, bad id
• Logical Types may not be registered with empty interface…
• Logical Types must be registered with interface types.

AI-assisted analysis of apache/beam@12126d8942 (2026-09-13). Data as JSON: /api/errors/d83908c937709d6a. Report an issue: GitHub.

Appendix: source

Thrown at sdks/go/pkg/beam/core/runtime/graphx/schema/schema.go:87

// RegisterType converts the type to it's schema representation, and converts it back to
// a synthetic type so we can map from the synthetic type back to the user type.
// Recursively registers other named struct types in any component parts.
func RegisterType(ut reflect.Type) {
	defaultRegistry.RegisterType(ut)
}

// getUUID generates a UUID using the string form of the type name.
func getUUID(ut reflect.Type) string {
	// String produces non-empty output for pointer and slice types.
	typename := ut.String()
	hasher := fnv.New128a()
	if n, err := hasher.Write([]byte(typename)); err != nil || n != len(typename) {
		panic(fmt.Sprintf("unable to generate schema uuid for %s, wrote out %d bytes, want %d: err %v", typename, n, len(typename), err))
	}
	id, err := uuid.NewRandomFromReader(bytes.NewBuffer(hasher.Sum(nil)))
	if err != nil {
		panic(fmt.Sprintf("unable to genereate schema uuid for type %s: %v", typename, err))
	}
	return id.String()
}

// Registered returns whether the given type has been registered with
// the schema package.
func (r *Registry) Registered(ut reflect.Type) bool {
	r.reconcileRegistrations()
	r.rwmu.RLock()
	defer r.rwmu.RUnlock()
	_, ok := r.syntheticToUser[ut]
	return ok
}

var sdfRtrackerType = reflect.TypeOf((*sdf.RTracker)(nil)).Elem()

// RegisterType converts the type to it's schema representation, and converts it back to
// a synthetic type so we can map from the synthetic type back to the user type.

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