apache/beam · error

invalid float encoding for: %v

Error message

invalid float encoding for: %v

What it means

decFloat decodes a byte slice as a zig-zag varuint-encoded, byte-reversed 64-bit float. If the underlying decVarUintZ decode fails (malformed varint: truncated or overlong data), the coder wraps the failure as 'invalid float encoding'. It signals corrupted or mismatched encoded data, not a bad float value.

Source

Thrown at sdks/go/pkg/beam/core/runtime/coderx/float.go:47

func encFloat(v typex.T) []byte {
	var val float64
	switch n := v.(type) {
	case float32:
		val = float64(n)
	case float64:
		val = n
	default:
		panic(fmt.Sprintf("received unknown value type: want a float, got %T", n))
	}

	return encVarUintZ(bits.ReverseBytes64(math.Float64bits(val)))
}

func decFloat(t reflect.Type, data []byte) (typex.T, error) {
	uval, err := decVarUintZ(reflectx.Uint64, data)
	if err != nil {
		return nil, errors.Errorf("invalid float encoding for: %v", data)
	}

	n := math.Float64frombits(bits.ReverseBytes64(uval.(uint64)))
	switch t.Kind() {
	case reflect.Float64:
		return n, nil
	case reflect.Float32:
		return float32(n), nil
	default:
		panic(fmt.Sprintf("unreachable statement: expected a float, got %v", t))
	}
}

// NewFloat returns a coder for the given float type. It uses the same
// encoding scheme as the gob package.
func NewFloat(t reflect.Type) (*coder.CustomCoder, error) {
	switch t.Kind() {
	case reflect.Float32, reflect.Float64:

View on GitHub (pinned to 12126d8942)

Solutions

1. Verify the data was encoded with the same NewFloat coder (encFloat) that is being used to decode.
2. Check for truncation or corruption in the source (file, message queue) before decoding.
3. Log the offending data bytes to confirm they start with a valid uvarint prefix.
4. Re-write the dataset with the current coder if the encoding scheme changed between versions.

// validate a buffer before float decode
func validFloatEncoding(data []byte) bool {
    _, size := binary.Uvarint(data)
    return size > 0 && size <= len(data)
}

func isFloatCoder(c *coder.CustomCoder) bool { return c.Name == "float" }

val, err := customCoder.Decode(data)
if err != nil {
    if strings.Contains(err.Error(), "invalid float encoding") {
        log.Warnf("skipping corrupt float record: % x", data)
        return nil, nil // or route to a dead-letter output
    }
    return nil, err
}

When it happens

Trigger: Calling decFloat (via the 'float' custom coder's Decode) with bytes not produced by encFloat — e.g. decoded with the wrong coder, data truncated, or cross-language coder mismatch.

Common situations: Reading old data written with a different coder scheme, corrupt files/messages, or mixed SDK versions where float encoding differs.

Understand the failure class

Background: "Invalid ... format", "must be in format X", "does not look like a ..." — invalid argument format errors across CLI tools and libraries — this error's family across 17 libraries.

Related errors

• ReadSimpleRowHeader reading nils count: %v, %v
• invalid varintz encoding for: %v
• invalid varuintz encoding for: %v
• empty type
• ReadSimpleRowHeader expected no nils encoded count, got %v

AI-assisted analysis of apache/beam@12126d8942 (2026-09-13). Data as JSON: /api/errors/76bd876388efad41. Report an issue: GitHub.