Go udp connection dial once, and send many - go

Question

please consider this code below, it is a simplified version of a service. I launch a no. of goroutines as needed during its lifetime, and as they go about doing things, they need to send udp messages to a set destination.
package main
import (
"fmt"
"log"
"net"
"time"
)
const (
udp_dest = "192.168.1.200:514"
)
func main() {
fmt.Println("Hello")
message := "this is a test"
log_message(&message)
go worker(1)
go worker(2)
go worker(3)
go worker(4)
time.Sleep(3009 * time.Second)
}
func log_message(message *string) {
RemoteAddr, err := net.ResolveUDPAddr("udp", udp_dest)
if err != nil {
//fmt.Println("Err, net.ResolveUDPAddr", err)
return
}
conn, err := net.DialUDP("udp", nil, RemoteAddr)
if err != nil {
return
}
udp_message := fmt.Sprintf("<30> %s", *message)
Bytes, _ := conn.Write([]byte(udp_message))
log.Printf("Sent %d Bytes to %s\n", Bytes, udp_dest)
}
func worker(tag int) {
i := 0
for {
worker_message := fmt.Sprintf("Some message from worker%d, loop: %d", tag, i)
log_message(&worker_message)
// do some work..
time.Sleep(300 * time.Second)
i += 1
}
}
In my log_message, everytime it gets called we're calling net.DialUDP which I feel is wasteful. I tried experimenting with global variables &net.UDPConn et al, but could not get to work.
Please show how to achieve/optimize this? There's only one UDP destination, and I'd like the daemon to Dial once at its start, and then just Write as needed.
Thanks!
here's what I got so far:
package main
import (
"fmt"
"log"
"net"
"time"
)
const (
udp_dest = "192.168.1.200:514"
)
var (
myconn *net.UDPConn
)
func main() {
fmt.Println("Hello")
message := "this is a test"
log_message(&message)
go worker(1)
go worker(2)
go worker(3)
go worker(4)
time.Sleep(3009 * time.Second)
}
func log_message(message *string) {
if myconn == nil {
fmt.Println("Setting up myconn!")
RemoteAddr, err := net.ResolveUDPAddr("udp", udp_dest)
if err != nil {
//fmt.Println("Err, net.ResolveUDPAddr", err)
return
}
myconn, err = net.DialUDP("udp", nil, RemoteAddr)
if err != nil {
return
}
}
udp_message := fmt.Sprintf("<30> %s", *message)
Bytes, _ := myconn.Write([]byte(udp_message))
log.Printf("Sent %d Bytes to %s\n", Bytes, udp_dest)
}
func worker(tag int) {
i := 0
for {
worker_message := fmt.Sprintf("Some message from worker%d, loop: %d", tag, i)
log_message(&worker_message)
// do some work..
time.Sleep(10 * time.Second)
i += 1
}
}

Answer 1

You are almost there. Move the setup code to a function and call it before starting the goroutines.
func main() {
if err := setupLog(); err != nil {
log.Fatal(err)
}
fmt.Println("Hello")
... same as before
}
func setupLog() error {
fmt.Println("Setting up myconn!")
RemoteAddr, err := net.ResolveUDPAddr("udp", udp_dest)
if err != nil {
return err
}
myconn, err = net.DialUDP("udp", nil, RemoteAddr)
return err
}
func log_message(message *string) {
udp_message := fmt.Sprintf("<30> %s", *message)
Bytes, _ := myconn.Write([]byte(udp_message))
log.Printf("Sent %d Bytes to %s\n", Bytes, udp_dest)
}
The code in the question does not work because there's a data race on myconn.