GoogleCloudPlatform/microservices-demo · error

failed to empty cart

Error message

failed to empty cart

What it means

emptyCartHandler failed to empty the user's cart via fe.emptyCart (cartservice EmptyCart RPC). The error is wrapped as "failed to empty cart" and returned as HTTP 500 instead of redirecting to the home page.

Source

Thrown at src/frontend/handlers.go:244

	if err != nil {
		renderHTTPError(log, r, w, errors.Wrap(err, "could not retrieve product"), http.StatusInternalServerError)
		return
	}

	if err := fe.insertCart(r.Context(), sessionID(r), p.GetId(), int32(payload.Quantity)); err != nil {
		renderHTTPError(log, r, w, errors.Wrap(err, "failed to add to cart"), http.StatusInternalServerError)
		return
	}
	w.Header().Set("location", baseUrl + "/cart")
	w.WriteHeader(http.StatusFound)
}

func (fe *frontendServer) emptyCartHandler(w http.ResponseWriter, r *http.Request) {
	log := r.Context().Value(ctxKeyLog{}).(logrus.FieldLogger)
	log.Debug("emptying cart")

	if err := fe.emptyCart(r.Context(), sessionID(r)); err != nil {
		renderHTTPError(log, r, w, errors.Wrap(err, "failed to empty cart"), http.StatusInternalServerError)
		return
	}
	w.Header().Set("location", baseUrl + "/")
	w.WriteHeader(http.StatusFound)
}

func (fe *frontendServer) viewCartHandler(w http.ResponseWriter, r *http.Request) {
	log := r.Context().Value(ctxKeyLog{}).(logrus.FieldLogger)
	log.Debug("view user cart")
	currencies, err := fe.getCurrencies(r.Context())
	if err != nil {
		renderHTTPError(log, r, w, errors.Wrap(err, "could not retrieve currencies"), http.StatusInternalServerError)
		return
	}
	cart, err := fe.getCart(r.Context(), sessionID(r))
	if err != nil {
		renderHTTPError(log, r, w, errors.Wrap(err, "could not retrieve cart"), http.StatusInternalServerError)
		return

View on GitHub (pinned to 72ba613a05)

Solutions

1. Check cartservice health and logs.
2. Verify CART_SERVICE_ADDR env configuration in frontend.
3. Check the redis backend used by cartservice.
4. Ensure sessionID(r) produces a valid non-empty user id; otherwise fix session cookie handling.

Example fix

// before
if err := fe.emptyCart(r.Context(), sessionID(r)); err != nil {
// after
if sessionID(r) == "" {
    http.Redirect(w, r, baseUrl+"/", http.StatusFound)
    return
}
if err := fe.emptyCart(r.Context(), sessionID(r)); err != nil {

uid := sessionID(r)
if uid == "" {
    http.Redirect(w, r, baseUrl+"/", http.StatusFound)
    return
}

func hasSession(r *http.Request) bool { return sessionID(r) != "" }

if err := fe.emptyCart(r.Context(), sessionID(r)); err != nil {
    log.WithField("error", err).Warn("failed to empty cart")
    renderHTTPError(log, r, w, errors.Wrap(err, "failed to empty cart"), http.StatusInternalServerError)
    return
}

When it happens

Trigger: POST /cart/empty when cartservice EmptyCart returns an error: service unavailable, timeout, or an invalid/empty session user id rejected by the cart service.

Common situations: cartservice down or restarting, redis backend unreachable, session/user id missing or malformed (empty session cookie leading to an invalid empty-cart request).

Related errors

• failed to add to cart
• failed to get user cart during checkout: %+v
• failed to empty user cart during checkout: %+v
• could not retrieve cart
• failed to convert currency

AI-assisted analysis of GoogleCloudPlatform/microservices-demo@72ba613a05 (2026-09-02). Data as JSON: /api/errors/cbfb15a0c0c79e74. Report an issue: GitHub.