What causes "marshalling failed" in hyperledger/fabric?

Run go mod tidy / go mod vendor to fix fabric-protos-go-apiv2 and protobuf runtime version mismatch

marshalling failed

Error message

marshalling failed

What it means

In localMSPPrincipalGetter.Get, when role == Admins the code builds an MSPRole proto (ADMIN + local MSP id) and marshals it with proto.Marshal. 'marshalling failed' wraps any protobuf serialization error. In practice this is nearly unreachable with a valid local MSP since MSPRole contains only a string and an enum.

Source

Thrown at core/policy/principal.go:58

		localMSP: localMSP,
	}
}

type localMSPPrincipalGetter struct {
	localMSP msp.MSP
}

func (m *localMSPPrincipalGetter) Get(role string) (*protomsp.MSPPrincipal, error) {
	mspid, err := m.localMSP.GetIdentifier()
	if err != nil {
		return nil, errors.WithMessage(err, "could not extract local msp identifier")
	}

	switch role {
	case Admins:
		principalBytes, err := proto.Marshal(&protomsp.MSPRole{Role: protomsp.MSPRole_ADMIN, MspIdentifier: mspid})
		if err != nil {
			return nil, errors.Wrap(err, "marshalling failed")
		}

		return &protomsp.MSPPrincipal{
			PrincipalClassification: protomsp.MSPPrincipal_ROLE,
			Principal:               principalBytes,
		}, nil
	case Members:
		principalBytes, err := proto.Marshal(&protomsp.MSPRole{Role: protomsp.MSPRole_MEMBER, MspIdentifier: mspid})
		if err != nil {
			return nil, errors.Wrap(err, "marshalling failed")
		}

		return &protomsp.MSPPrincipal{
			PrincipalClassification: protomsp.MSPPrincipal_ROLE,
			Principal:               principalBytes,
		}, nil
	default:
		return nil, errors.Errorf("MSP Principal role [%s] not recognized", role)

View on GitHub (pinned to 2736b63f8f)

Solutions

Run go mod tidy / go mod vendor to fix fabric-protos-go-apiv2 and protobuf runtime version mismatch
Rebuild the binary to clear corrupted vendor state
Inspect the wrapped error (errors.Cause) for the underlying marshal reason

Example fix

// before
principalBytes, err := proto.Marshal(&protomsp.MSPRole{Role: protomsp.MSPRole_ADMIN, MspIdentifier: mspid})
if err != nil { return nil, errors.Wrap(err, "marshalling failed") }
// after
principalBytes, err := proto.Marshal(&protomsp.MSPRole{Role: protomsp.MSPRole_ADMIN, MspIdentifier: mspid})
if err != nil { return nil, errors.Wrapf(err, "marshalling MSPRole ADMIN for msp %s failed", mspid) }

Defensive patterns

Strategy: try-catch

Validate before calling

if mspid == "" {
    return errors.New("local MSP identifier is empty; MSP not initialized")
}

Try / catch

principal, err := getter.Get("Admins")
if err != nil {
    if strings.Contains(err.Error(), "marshalling failed") {
        return fmt.Errorf("protobuf serialization failure for ADMIN principal: %w", err)
    }
    return err
}

Prevention

Pin compatible versions of fabric-protos-go-apiv2 and google.golang.org/protobuf
Run go mod verify / go mod tidy in CI to catch corrupted vendor trees
Treat any occurrence as an environment/build defect, not a runtime data problem

When it happens

Trigger: proto.Marshal fails while serializing the MSPRole{Role: ADMIN, MspIdentifier: mspid} message inside Get("Admins") — realistically only from a corrupted protobuf runtime/registry state or an invalid MspIdentifier string causing serialization issues.

Common situations: Mismatched or broken fabric-protos-go-apiv2 / google.golang.org/protobuf dependency versions during custom builds or vendor corruption; regression tests injecting a mock local MSP whose GetIdentifier returns pathological data.

Related errors

AI-assisted analysis of hyperledger/fabric@2736b63f8f (2026-09-04). Data as JSON: /api/errors/2248158c86f18153. Report an issue: GitHub.