Basic working locally

main.go

@@ -12,16 +12,16 @@ import (
 )
 
 func main() {
-	// Connect to NATS server
+	// Connect to the NATS server
 	nc, err := nats.Connect(nats.DefaultURL)
 	if err != nil {
-		log.Fatal(err)
+		log.Fatal("Error connecting to NATS:", err)
 	}
 	defer nc.Close()
 
-	// HTTP handler function
+	// HTTP handler to proxy all requests to NATS
 	http.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
-		// Read the request body
+		// Read the entire request body (if any)
 		body, err := ioutil.ReadAll(r.Body)
 		if err != nil {
 			http.Error(w, "Error reading request body", http.StatusInternalServerError)
@@ -29,44 +29,55 @@ func main() {
 		}
 		defer r.Body.Close()
 
-		// Drop the leading slash if there is one, and replace slashes with dots.
-		subject := strings.ReplaceAll(strings.TrimPrefix(r.URL.Path, "/"), "/", ".")
+		// Create the NATS subject.
+		// Remove the leading slash from the path and replace remaining slashes with dots.
+		// The subject is prefixed with "http.<method>.", where <method> is lower-case.
+		path := strings.TrimPrefix(r.URL.Path, "/")
+		subjectPath := strings.ReplaceAll(path, "/", ".")
+		subject := fmt.Sprintf("http.%s.%s", strings.ToLower(r.Method), subjectPath)
 
-		// Create a NATS message with the request body and headers
+		log.Println("Forwarding HTTP", r.Method, "request on", r.URL.Path, "to NATS subject:", subject)
+
+		// Create a new NATS message with the HTTP request body
 		msg := nats.Msg{
-			Subject: fmt.Sprintf("http.%s", subject),
+			Subject: subject,
 			Data:    body,
 			Header:  nats.Header{},
 		}
-		log.Println("subject:", msg.Subject)
 
-		// Copy HTTP headers to NATS message headers
+		// Copy over all the HTTP request headers to the NATS message headers
 		for key, values := range r.Header {
 			for _, value := range values {
 				msg.Header.Add(key, value)
 			}
 		}
 
-		// Send request to NATS and wait for reply
+		// Add additional HTTP meta-data as headers
+		msg.Header.Set("X-HTTP-Method", r.Method)
+		msg.Header.Set("X-HTTP-Path", r.URL.Path)
+		msg.Header.Set("X-HTTP-Query", r.URL.RawQuery)
+		msg.Header.Set("X-Remote-Addr", r.RemoteAddr)
+
+		// Send the NATS request and wait synchronously for a reply (timeout: 30 seconds)
 		reply, err := nc.RequestMsg(&msg, 30*time.Second)
 		if err != nil {
 			http.Error(w, "Error processing request", http.StatusInternalServerError)
-			log.Println("Error processing the request", err)
+			log.Println("NATS request error:", err)
 			return
 		}
 
-		// Copy NATS reply headers to HTTP response
+		// Set any response headers from the NATS reply on the HTTP response
 		for key, values := range reply.Header {
 			for _, value := range values {
 				w.Header().Add(key, value)
 			}
 		}
 
-		// Write NATS reply body to HTTP response
+		// Write the reply body (from NATS) back to the HTTP client
 		w.Write(reply.Data)
 	})
 
-	// Start HTTP server
+	// Start the HTTP server
 	fmt.Println("Server is running on http://localhost:8080")
 	log.Fatal(http.ListenAndServe(":8080", nil))
 }