func (h *multiHopHandler) Handle(ctx context.Context, reqMeta yarpc.ReqMeta, body interface{}) (interface{}, yarpc.ResMeta, error) {
	if h.phoneClient == nil {
		panic("call SetClient() and SetTransport() first")
	}

	assertBaggageMatches(ctx, h.t, h.wantBaggage)

	span := opentracing.SpanFromContext(ctx)
	for key, value := range h.addBaggage {
		span.SetBaggageItem(key, value)
	}
	ctx = opentracing.ContextWithSpan(ctx, span)

	var resp js.RawMessage
	phoneResMeta, err := h.phoneClient.Call(
		ctx,
		yarpc.NewReqMeta().Procedure("phone").Headers(reqMeta.Headers()),
		&server.PhoneRequest{
			Service:   "ctxclient",
			Procedure: h.phoneCallTo,
			Transport: h.phoneCallTransport,
			Body:      &js.RawMessage{'{', '}'},
		}, &resp)

	resMeta := yarpc.NewResMeta().Headers(phoneResMeta.Headers())
	return map[string]interface{}{}, resMeta, err
}

// Phone implements the phone procedure
func Phone(ctx context.Context, reqMeta yarpc.ReqMeta, body *PhoneRequest) (*PhoneResponse, yarpc.ResMeta, error) {
	var outbound transport.UnaryOutbound

	switch {
	case body.Transport.HTTP != nil:
		t := body.Transport.HTTP
		url := fmt.Sprintf("http://%s:%d", t.Host, t.Port)
		outbound = ht.NewOutbound(url)
	case body.Transport.TChannel != nil:
		t := body.Transport.TChannel
		hostport := fmt.Sprintf("%s:%d", t.Host, t.Port)
		ch, err := tchannel.NewChannel("yarpc-test-client", nil)
		if err != nil {
			return nil, nil, fmt.Errorf("failed to build TChannel: %v", err)
		}
		outbound = tch.NewOutbound(ch, tch.HostPort(hostport))
	default:
		return nil, nil, fmt.Errorf("unconfigured transport")
	}

	if err := outbound.Start(transport.NoDeps); err != nil {
		return nil, nil, err
	}
	defer outbound.Stop()

	// TODO use reqMeta.Service for caller
	client := json.New(channel.MultiOutbound("yarpc-test", body.Service, transport.Outbounds{
		Unary: outbound,
	}))
	resBody := PhoneResponse{
		Service:   "yarpc-test", // TODO use reqMeta.Service
		Procedure: reqMeta.Procedure(),
	}

	ctx, cancel := context.WithTimeout(ctx, 500*time.Millisecond)
	defer cancel()
	_, err := client.Call(
		ctx,
		yarpc.NewReqMeta().Procedure(body.Procedure),
		body.Body,
		&resBody.Body)
	if err != nil {
		return nil, nil, err
	}

	return &resBody, nil, nil
}

func resMetaFromReqMeta(reqMeta yarpc.ReqMeta) yarpc.ResMeta {
	return yarpc.NewResMeta().Headers(reqMeta.Headers())
}

func (h helloHandler) Echo(ctx context.Context, reqMeta yarpc.ReqMeta, e *echo.EchoRequest) (*echo.EchoResponse, yarpc.ResMeta, error) {
	return &echo.EchoResponse{Message: e.Message, Count: e.Count + 1},
		yarpc.NewResMeta().Headers(reqMeta.Headers()),
		nil
}

func yarpcEcho(ctx context.Context, reqMeta yarpc.ReqMeta, body []byte) ([]byte, yarpc.ResMeta, error) {
	return body, yarpc.NewResMeta().Headers(reqMeta.Headers()), nil
}

// Echo endpoint for the Echo service.
func (EchoThrift) Echo(ctx context.Context, reqMeta yarpc.ReqMeta, ping *echo.Ping) (*echo.Pong, yarpc.ResMeta, error) {
	return &echo.Pong{Boop: ping.Beep}, yarpc.NewResMeta().Headers(reqMeta.Headers()), nil
}

// EchoJSON implements the echo procedure.
func EchoJSON(ctx context.Context, reqMeta yarpc.ReqMeta, body map[string]interface{}) (map[string]interface{}, yarpc.ResMeta, error) {
	return body, yarpc.NewResMeta().Headers(reqMeta.Headers()), nil
}