What causes "unrecognized message type: %v" in micro/go-micro?

Use a message Type supported by the jsonrpc codec (Request/Response as implemented).

unrecognized message type: %v

Error message

unrecognized message type: %v

What it means

The jsonrpc codec's Write method switches on the codec.MessageType (Request, Response, etc.) to decide how to serialize the message. Any message type it does not explicitly handle falls through to default and yields this error, meaning the codec cannot encode the given message kind.

Source

Thrown at codec/jsonrpc/jsonrpc.go:44

func (j *jsonCodec) String() string {
	return "json-rpc"
}

func (j *jsonCodec) Write(m *codec.Message, b interface{}) error {
	switch m.Type {
	case codec.Request:
		return j.c.Write(m, b)
	case codec.Response, codec.Error:
		return j.s.Write(m, b)
	case codec.Event:
		data, err := json.Marshal(b)
		if err != nil {
			return err
		}
		_, err = j.rwc.Write(data)
		return err
	default:
		return fmt.Errorf("unrecognized message type: %v", m.Type)
	}
}

func (j *jsonCodec) ReadHeader(m *codec.Message, mt codec.MessageType) error {
	j.buf.Reset()
	j.mt = mt

	switch mt {
	case codec.Request:
		return j.s.ReadHeader(m)
	case codec.Response:
		return j.c.ReadHeader(m)
	case codec.Event:
		_, err := io.Copy(j.buf, j.rwc)
		return err
	default:
		return fmt.Errorf("unrecognized message type: %v", mt)
	}

View on GitHub (pinned to 24529f1404)

Solutions

Use a message Type supported by the jsonrpc codec (Request/Response as implemented).
Switch to the appropriate codec for that message type (e.g. bytes or grpc codec supports more flows).
Verify the client/server configuration is not routing Event/Publish traffic through the jsonrpc codec.
Check that codec.Message.Type is set explicitly, not left as zero value.

Example fix

// before
msg.Type = codec.Event
jcodec.Write(msg, body)
// after
msg.Type = codec.Request
jcodec.Write(msg, body)

Defensive patterns

Strategy: type-guard

Validate before calling

func jsonrpcSupports(mt codec.MessageType) bool {
	return mt == codec.Request || mt == codec.Response || mt == codec.Event
}

Type guard

func isJsonrpcWritable(m *codec.Message) bool {
	return m != nil && jsonrpcSupports(m.Type)
}

Try / catch

if err := c.Write(msg, body); err != nil {
	if strings.HasPrefix(err.Error(), "unrecognized message type") {
		// unsupported MessageType for this codec; use another codec or fix msg.Type
	}
	return err
}

Prevention

Set codec.Message.Type explicitly and to a supported value.
Do not route Event/publish traffic through codecs that do not implement it.
Prefer built-in transports that assign message types for you.
Add a switch-level test enumerating every MessageType your flow uses.

When it happens

Trigger: Calling Write on a jsonrpc codec with a message whose Type is not one of the handled types (e.g. codec.Event if unhandled, or a zero-value MessageType).

Common situations: Custom transport code sending raw codec.Message values with a hand-set Type; framework internals publishing events through a client configured with the jsonrpc codec that does not support that message type; constructing codec.Message manually in tests.

Related errors

AI-assisted analysis of micro/go-micro@24529f1404 (2026-09-01). Data as JSON: /api/errors/a626f810cb01d453. Report an issue: GitHub.