GoogleCloudPlatform/microservices-demo · error

failed to unmarshal body

Error message

failed to unmarshal body

What it means

json.Unmarshal failed to decode the assistant's response body into LLMResponse ({content, details}). The assistant replied, but the body is not valid JSON or does not match the expected schema (HTML error page, empty body, or version drift).

Source

Thrown at src/frontend/handlers.go:489

	req.Header.Set("Accept", "application/json")
	res, err := http.DefaultClient.Do(req)
	if err != nil {
		renderHTTPError(log, r, w, errors.Wrap(err, "failed to send request"), http.StatusInternalServerError)
		return
	}

	body, err := io.ReadAll(res.Body)
	if err != nil {
		renderHTTPError(log, r, w, errors.Wrap(err, "failed to read response"), http.StatusInternalServerError)
		return
	}

	fmt.Printf("%+v\n", body)
	fmt.Printf("%+v\n", res)

	err = json.Unmarshal(body, &response)
	if err != nil {
		renderHTTPError(log, r, w, errors.Wrap(err, "failed to unmarshal body"), http.StatusInternalServerError)
		return
	}

	// respond with the same message
	json.NewEncoder(w).Encode(Response{Message: response.Content})

	w.WriteHeader(http.StatusOK)
}

func (fe *frontendServer) setCurrencyHandler(w http.ResponseWriter, r *http.Request) {
	log := r.Context().Value(ctxKeyLog{}).(logrus.FieldLogger)
	cur := r.FormValue("currency_code")
	payload := validator.SetCurrencyPayload{Currency: cur}
	if err := payload.Validate(); err != nil {
		renderHTTPError(log, r, w, validator.ValidationErrorResponse(err), http.StatusUnprocessableEntity)
		return
	}
	log.WithField("curr.new", payload.Currency).WithField("curr.old", currentCurrency(r)).

View on GitHub (pinned to 72ba613a05)

Solutions

1. Check res.StatusCode before decoding; handle non-2xx responses (often non-JSON) separately.
2. Log the raw body to inspect the actual payload shape.
3. Align LLMResponse with the assistant's real schema or decode into a map first.
4. Ensure the assistant always returns application/json, even on internal errors.

When it happens

Trigger: Thrown at src/frontend/handlers.go:489 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of GoogleCloudPlatform/microservices-demo@72ba613a05 (2026-09-02). Data as JSON: /api/errors/d9acdb54e45f1ec1. Report an issue: GitHub.