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package main
import (
"flag"
"fmt"
"io/ioutil"
"log"
"net/http"
"os"
"strings"
"time"
"github.com/nats-io/nats.go"
)
// printHelp outputs the usage information.
func printHelp() {
fmt.Println("Usage: HTTP-to-NATS proxy server")
fmt.Println("\nThe following environment variables are supported:")
fmt.Println(" NATS_URL - NATS connection URL (default: nats://127.0.0.1:4222)")
fmt.Println(" NATS_USER - NATS username for authentication (optional)")
fmt.Println(" NATS_PASSWORD - NATS password for authentication (optional)")
fmt.Println(" HTTP_PORT - HTTP port to listen on (default: 8080)")
}
func main() {
helpFlag := flag.Bool("help", false, "Display help information about available environment variables")
flag.Parse()
if *helpFlag {
printHelp()
os.Exit(0)
}
// Read NATS connection info from environment variables
natsURL := os.Getenv("NATS_URL")
if natsURL == "" {
natsURL = nats.DefaultURL // defaults to "nats://127.0.0.1:4222"
}
natsUser := os.Getenv("NATS_USER")
natsPassword := os.Getenv("NATS_PASSWORD")
// Read HTTP port from environment variables
httpPort := os.Getenv("HTTP_PORT")
if httpPort == "" {
httpPort = "8080"
}
// Set up NATS connection options if authentication info is provided.
var opts []nats.Option
if natsUser != "" && natsPassword != "" {
opts = append(opts, nats.UserInfo(natsUser, natsPassword))
}
nc, err := nats.Connect(natsURL, opts...)
if err != nil {
log.Fatal("Error connecting to NATS:", err)
}
defer nc.Close()
// HTTP handler function
http.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
// Read the entire request body
body, err := ioutil.ReadAll(r.Body)
if err != nil {
http.Error(w, "Error reading request body", http.StatusInternalServerError)
return
}
defer r.Body.Close()
// Drop the leading slash, replace remaining slashes with dots to form the subject
subject := strings.ReplaceAll(strings.TrimPrefix(r.URL.Path, "/"), "/", ".")
// Prefix the subject with "http." to follow the convention
msg := nats.Msg{
Subject: fmt.Sprintf("http.%s", subject),
Data: body,
Header: nats.Header{},
}
log.Println("Forwarding request to subject:", msg.Subject)
// Copy HTTP 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 (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)
return
}
// Copy headers from the NATS reply to 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
w.Write(reply.Data)
})
fmt.Println("Server is running on http://localhost:" + httpPort)
log.Fatal(http.ListenAndServe(":"+httpPort, nil))
}
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