lib/httpserver: log the client address additionally to the requestURI in the SendPrometheusError()

This should allow detecting the client, which led to the error logged via SendPrometheusError() function,
e.g. this improves troubleshooting of the logged errors.

This is a follow-up for c9bb4ddeed

lib/httpserver/httpserver.go

@@ -653,10 +653,7 @@ func (rwa *responseWriterWithAbort) abort() {
 // Errorf writes formatted error message to w and to logger.
 func Errorf(w http.ResponseWriter, r *http.Request, format string, args ...any) {
 	errStr := fmt.Sprintf(format, args...)
-	remoteAddr := GetQuotedRemoteAddr(r)
-	requestURI := GetRequestURI(r)
-	errStr = fmt.Sprintf("remoteAddr: %s; requestURI: %s; %s", remoteAddr, requestURI, errStr)
-	logger.WarnfSkipframes(1, "%s", errStr)
+	logHTTPError(r, errStr)
 
 	// Extract statusCode from args
 	statusCode := http.StatusBadRequest
@@ -678,6 +675,14 @@ func Errorf(w http.ResponseWriter, r *http.Request, format string, args ...any)
 	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.

lib/httpserver/prometheus.go

@@ -3,15 +3,14 @@ package httpserver
 import (
 	"errors"
 	"net/http"
-
-	"github.com/VictoriaMetrics/VictoriaMetrics/lib/logger"
 )
 
 // SendPrometheusError sends err to w in Prometheus querying API response format.
 //
 // See https://prometheus.io/docs/prometheus/latest/querying/api/#format-overview for more details
 func SendPrometheusError(w http.ResponseWriter, r *http.Request, err error) {
-	logger.WarnfSkipframes(1, "error in %q: %s", GetRequestURI(r), err)
+	errStr := err.Error()
+	logHTTPError(r, errStr)
 
 	w.Header().Set("Content-Type", "application/json")
 	statusCode := http.StatusUnprocessableEntity