response.WriteHeader method has been called more than once while handling an HTTP request

[Xib1uvXi]

What happened:

Environment:

• Kratos version (use kratos -v):
• Go version (use go version): go version go1.23.2
• OS (e.g: cat /etc/os-release): linux / arm64

[Xib1uvXi]

Kratos version: v2.8.2

[dosubot]

Hey @Xib1uvXi! I'm here to assist you with any Kratos issues you're facing. I can help you with bug fixes, answer questions, and guide you on becoming a contributor. Let's tackle this together!

The issue with response.WriteHeader being called more than once in the Go-Kratos framework, specifically from the http.DefaultErrorEncoder in codec.go at line 116, occurs because WriteHeader is called both when an error occurs during marshaling and again after setting the content type and before writing the response body.

To resolve this issue, ensure that WriteHeader is only called once. You can modify the DefaultErrorEncoder function to set a flag or return early if WriteHeader has already been called due to an error. Here's a possible solution:

func DefaultErrorEncoder(w http.ResponseWriter, r *http.Request, err error) {
    se := errors.FromError(err)
    codec, _ := CodecForRequest(r, "Accept")
    body, marshalErr := codec.Marshal(se)
    if marshalErr != nil {
        w.WriteHeader(http.StatusInternalServerError)
        return
    }
    w.Header().Set("Content-Type", httputil.ContentType(codec.Name()))
    if !w.Header().Written() { // Check if WriteHeader has already been called
        w.WriteHeader(int(se.Code))
    }
    _, _ = w.Write(body)
}

This solution assumes that w.Header().Written() is a method that checks if WriteHeader has already been called. If such a method does not exist, you may need to implement a custom mechanism to track whether WriteHeader has been called ^[1].

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