hyperledger/fabric · error

error encoding output

Error message

error encoding output

What it means

protolator.DeepMarshalJSON failed while writing the decoded proto as JSON to the --output file. This wraps either a JSON marshaling error inside protolator or an underlying write error on the output file.

Source

Thrown at cmd/configtxlator/main.go:187

	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)
	if err != nil {
		return errors.Wrapf(err, "error unmarshalling original config")
	}

	updtIn, err := io.ReadAll(updated)

View on GitHub (pinned to 2736b63f8f)

Solutions

1. Check output path is writable and its directory exists
2. Re-run to a local temp file then move it into place
3. Verify the message type contains only fields protolator supports (stock fabric-protos types)
4. Check available disk space

Example fix

// before
configtxlator decode --input config.pb --output /readonly/config.json --type common.Config
// after
configtxlator decode --input config.pb --output /tmp/config.json --type common.Config && mv /tmp/config.json /readonly/config.json

if [ ! -w "$(dirname "$OUTPUT")" ]; then echo "output dir not writable" >&2; exit 1; fi

out, err := cmd.CombinedOutput()
if err != nil && strings.Contains(string(out), "error encoding output") {
    // write to temp file, then move
}

When it happens

Trigger: Output file not writable (permissions, read-only mount, disk full), or protolator failing to convert an unusual/unknown field of the message to JSON.

Common situations: Writing to a container path mounted read-only, output directory missing, or custom proto extensions that protolator cannot represent.

Understand the failure class

Background: "failed to write file", "Could not save figure", "Error saving remote file" — file write failed: causes and fixes across languages and libraries — this error's family across 38 libraries.

Related errors

• error reading input
• error unmarshalling
• error reading original config
• error unmarshalling original config
• error reading updated config

AI-assisted analysis of hyperledger/fabric@2736b63f8f (2026-09-04). Data as JSON: /api/errors/f2cbb3aecf39a447. Report an issue: GitHub.