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package main
import (
"fmt"
"io/ioutil"
"log"
"net/http"
"strings"
"time"
"github.com/nats-io/nats.go"
)
func main() {
// Connect to the NATS server
nc, err := nats.Connect(nats.DefaultURL)
if err != nil {
log.Fatal("Error connecting to NATS:", err)
}
defer nc.Close()
// HTTP handler to proxy all requests to NATS
http.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
// 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)
return
}
defer r.Body.Close()
// 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)
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: subject,
Data: body,
Header: nats.Header{},
}
// 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)
}
}
// 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("NATS request error:", err)
return
}
// 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 the reply body (from NATS) back to the HTTP client
w.Write(reply.Data)
})
// Start the HTTP server
fmt.Println("Server is running on http://localhost:8080")
log.Fatal(http.ListenAndServe(":8080", nil))
}
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