very rudimentary impl

llmproxymetrics.go

@@ -0,0 +1,105 @@
+package main
+
+import (
+	"bytes"
+	"encoding/json"
+	"fmt"
+	"log"
+	"net/http"
+	"net/http/httptest"
+	"net/http/httputil"
+	"net/url"
+	"strconv"
+	"time"
+
+	"github.com/caarlos0/env/v11"
+)
+
+var cfg config
+
+type config struct {
+	BaseURL string `env:"BASE_URL"`
+	Port    int    `env:"PORT"`
+}
+
+func createProxy(target *url.URL) func(http.ResponseWriter, *http.Request) {
+	return func(w http.ResponseWriter, r *http.Request) {
+		r.Host = target.Host
+		r.URL.Scheme = target.Scheme
+		r.URL.Host = target.Host
+
+		lrw := &LoggingResponseWriter{ResponseWriter: w, body: new(bytes.Buffer)}
+		proxy := httputil.NewSingleHostReverseProxy(target)
+
+		startTime := time.Now()
+		recorder := httptest.NewRecorder()
+		proxy.ServeHTTP(recorder, r)
+
+		responseBody := recorder.Body.Bytes()
+
+		var jsonResponse map[string]interface{}
+		err := json.Unmarshal(responseBody, &jsonResponse)
+		if err != nil {
+			log.Printf("Error unmarshalling JSON response: %v", err)
+			lrw.Write(responseBody)
+			return
+		}
+
+		// Add your metrics metadata here
+		jsonResponse["metrics"] = map[string]interface{}{
+			"requestPath":  r.URL.Path,
+			"statusCode":   recorder.Code,
+			"responseTime": time.Since(startTime).Milliseconds(),
+			// Add more metrics as needed
+		}
+
+		modifiedResponseBody, err := json.Marshal(jsonResponse)
+		if err != nil {
+			log.Printf("Error marshalling modified JSON response: %v", err)
+			lrw.Write(responseBody)
+			return
+		}
+
+		for name, values := range recorder.Header() {
+			for _, value := range values {
+				w.Header().Add(name, value)
+			}
+		}
+
+		w.WriteHeader(recorder.Code)
+		lrw.Write(modifiedResponseBody)
+
+		log.Printf("Response with metrics: %s", lrw.Body())
+	}
+}
+
+type LoggingResponseWriter struct {
+	http.ResponseWriter
+	body *bytes.Buffer
+}
+
+func (lrw *LoggingResponseWriter) Write(b []byte) (int, error) {
+	lrw.body.Write(b)
+	return lrw.ResponseWriter.Write(b)
+}
+
+func (lrw *LoggingResponseWriter) Body() string {
+	return lrw.body.String()
+}
+
+func main() {
+	env.Parse(&cfg)
+
+	targetURL, err := url.Parse(cfg.BaseURL)
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	http.HandleFunc("/", createProxy(targetURL))
+
+	log.Printf("Starting proxy server on :%s", strconv.Itoa(cfg.Port))
+	err = http.ListenAndServe(fmt.Sprintf(":%s", strconv.Itoa(cfg.Port)), nil)
+	if err != nil {
+		log.Fatal(err)
+	}
+}