VictoriaMetrics/VictoriaMetrics · error

%s

Error message

%s

What it means

httpserver.Errorf writes a formatted error to the client and logs it with remote address and request URI. If response headers were already sent (responseWriterWithAbort.sentHeaders), it cannot send a status code, so it writes the (unescaped to wire, HTML-escaped variant when streaming) message into the body and aborts the connection to break keep-alive — the surfaced message is just the formatted errStr. Otherwise it calls http.Error with a status extracted from any ErrorWithStatusCode argument (default 400).

Source

Thrown at lib/httpserver/httpserver.go:782

	for _, arg := range args {
		if err, ok := arg.(error); ok && errors.As(err, &esc) {
			statusCode = esc.StatusCode
			break
		}
	}

	if rwa, ok := w.(*responseWriterWithAbort); ok && rwa.sentHeaders {
		// HTTP status code has been already sent to client, so it cannot be sent again.
		// Just write errStr to the response and abort the client connection, so the client could notice the error.
		//
		// HTML-escape the errStr in order to protect from possible XSS, since the errStr may contain user input.
		errStrEscaped := html.EscapeString(errStr)

		fmt.Fprintf(w, "\n%s\n", errStrEscaped)
		rwa.abort()
		return
	}
	http.Error(w, errStr, statusCode)
}

// logHTTPError logs the errStr with the client remote address and the request URI obtained from r.
func logHTTPError(r *http.Request, errStr string) {
	remoteAddr := GetQuotedRemoteAddr(r)
	requestURI := GetRequestURI(r)
	errStr = fmt.Sprintf("remoteAddr: %s; requestURI: %s; %s", remoteAddr, requestURI, errStr)
	logger.WarnfSkipframes(2, "%s", errStr)
}

// ErrorWithStatusCode is error with HTTP status code.
//
// The given StatusCode is sent to client when the error is passed to Errorf.
type ErrorWithStatusCode struct {
	Err        error
	StatusCode int
}

View on GitHub (pinned to 5079fb58f1)

Solutions

1. Read the response body / server log line (remoteAddr, requestURI, message) to identify the actual handler error
2. Fix the client request that triggered the handler error (correct path, query params, payload)
3. If the connection is being aborted mid-response, check server logs for the underlying cause rather than the truncated client message

// validate request before hitting the server
if !strings.HasPrefix(path, "/api/v1/") && !knownPaths[path] {
    return fmt.Errorf("path %q is not supported; check server logs via Errorf output", path)
}

func isHTTPServerError(err error) (*httpserver.ErrorWithStatusCode, bool) {
    var esc *httpserver.ErrorWithStatusCode
    ok := errors.As(err, &esc)
    return esc, ok
}

resp, err := doRequest(req)
if err != nil {
    return err
}
if resp.StatusCode >= 400 {
    body, _ := io.ReadAll(io.LimitReader(resp.Body, 4096))
    return fmt.Errorf("server rejected request (status %d): %s", resp.StatusCode, strings.TrimSpace(string(body)))
}
// mid-stream abort case: headers already sent, connection closed
if resp.Header.Get("Connection") == "close" && bodyTruncated {
    return fmt.Errorf("response aborted mid-stream; check server log for Errorf message")
}

When it happens

Trigger: Handlers calling Errorf(w, r, format, args...) — e.g. unsupported paths, invalid query params, insert/query failures — including when the status code was already committed and the connection must be aborted mid-response.

Common situations: Clients requesting unknown paths or malformed queries; errors occurring mid-stream after headers were sent (client sees truncated body plus aborted keep-alive connection); an ErrorWithStatusCode in args propagating 503s from the insert limiter.

Related errors

• cannot perform http request to %q: %w
• cannot read response from %q: %w
• cannot get credentials from %s: %w
• cannot fetch %q: %w
• cannot gracefully shutdown http server at %q in %.3fs; proba

AI-assisted analysis of VictoriaMetrics/VictoriaMetrics@5079fb58f1 (2026-09-03). Data as JSON: /api/errors/87095911ed1684d6. Report an issue: GitHub.