hyperledger/fabric · error

error unmarshalling

Error message

error unmarshalling

What it means

proto.Unmarshal rejected the input bytes while decoding to the requested message type. "error unmarshalling" means the binary data is not a valid wire-format encoding of the --type message (truncated, corrupted, or actually a different message/encoding such as JSON).

Source

Thrown at cmd/configtxlator/main.go:182

	if err != nil {
		return errors.Wrapf(err, "error encode input")
	}

	msgType := reflect.TypeOf(mt.Zero().Interface())

	if msgType == nil {
		return errors.Errorf("message of type %s unknown", msgType)
	}
	msg := reflect.New(msgType.Elem()).Interface().(proto.Message)

	in, err := io.ReadAll(input)
	if err != nil {
		return errors.Wrapf(err, "error reading input")
	}

	err = proto.Unmarshal(in, msg)
	if err != nil {
		return errors.Wrapf(err, "error unmarshalling")
	}

	err = protolator.DeepMarshalJSON(output, msg)
	if err != nil {
		return errors.Wrapf(err, "error encoding output")
	}

	return nil
}

func computeUpdt(original, updated, output *os.File, channelID string) error {
	origIn, err := io.ReadAll(original)
	if err != nil {
		return errors.Wrapf(err, "error reading original config")
	}

	origConf := &cb.Config{}
	err = proto.Unmarshal(origIn, origConf)

View on GitHub (pinned to 2736b63f8f)

Solutions

1. Confirm input is binary proto, not JSON; use `encode` for JSON→pb and `decode` for pb→JSON
2. Validate bytes with `protoc --decode_raw < config.pb` to see actual wire content
3. Match the --type to what was originally encoded (common.Config vs common.ConfigUpdate)
4. Re-export the config from the ordering service if the file is truncated/corrupt

Example fix

// before
configtxlator decode --input config.json --output config.pb --type common.Config
// after
configtxlator encode --input config.json --output config.pb --type common.Config

// sniff binary vs JSON before decode
head -c1 "$INPUT" | grep -q '{' && echo "input is JSON; use encode, not decode" && exit 1

out, err := cmd.CombinedOutput()
if err != nil && strings.Contains(string(out), "error unmarshalling") {
    return fmt.Errorf("input is not valid binary proto for the given --type: %w", err)
}

When it happens

Trigger: Feeding a JSON config back into decode (wrong direction), decoding with the wrong --type so fields don't line up, truncated file from a failed export, or base64-encoded bytes not decoded first.

Common situations: Swapping encode/decode flags in scripts, editing a .pb file by hand, pulling a partial block of a channel config, or decoding a ConfigUpdate payload as common.Config.

Understand the failure class

Background: "cannot parse invalid wire-format data", "cannot unmarshal", "failed unmarshalling": protobuf unmarshal errors explained — this error's family across 10 libraries.

Related errors

• error unmarshalling original config
• error unmarshalling updated config
• error encoding output
• failed to unmarshal ApplicationPolicy bytes
• could not unmarshal signature policy envelope

AI-assisted analysis of hyperledger/fabric@2736b63f8f (2026-09-04). Data as JSON: /api/errors/fa68628a3178aaa5. Report an issue: GitHub.