test golang with systemd socket load balance

cnet-net.go

// cnet/net.go
package cnet

import (
	"fmt"
	"log"
	"net"
	"os"
	"strconv"
	"strings"
	"syscall"
)

const (
	startFd = 3
)

var (
	listeners = make(map[string]net.Listener)
)

func init() {

	log.Printf("%#v\n", os.Environ())
	pid := os.Getenv("LISTEN_PID")
	fds, _ := strconv.Atoi(os.Getenv("LISTEN_FDS"))
	fdNames := strings.Split(os.Getenv("LISTEN_FDNAMES"), ":")

	log.Println(pid, fds, fdNames)

	if len(pid) <= 0 || fds <= 0 || len(fdNames) <= 0 {
		return
	}

	for fd := startFd; fd < startFd+fds; fd++ {
		syscall.CloseOnExec(fd)
		offset := fd - startFd
		name := fmt.Sprintf("LISTEN_FD_%d", fd)
		if offset < len(fdNames) && len(fdNames[offset]) > 0 {
			name = fdNames[offset]
		}
		log.Printf("PID: %d, FD:%d, uintptr:%v, name:%s\n", os.Getpid(), fd, uintptr(fd), name)
		file := os.NewFile(uintptr(fd), name)
		ln, err := net.FileListener(file)
		if err != nil {
			log.Printf("PID: %d, fderr: %s\n", os.Getpid(), err)
		}
		if listener, ok := ln.(*net.TCPListener); ok {
			addrS := listener.Addr().String()
			shost, sport, err := net.SplitHostPort(addrS)
			log.Printf("PID: %d, FD:%d, addr:%s, sh:%s, sp:%s, se:%s\n", os.Getpid(), fd, addrS, shost, sport, err)
			listeners[sport] = ln
		} else {
			log.Printf("PID: %d, FD:%d, not a TCPListener\n", os.Getpid(), fd)
		}
		file.Close()
	}

	log.Printf("%#v\n", listeners)
}

func Listen(addr string) (net.Listener, error) {
	_, sport, err := net.SplitHostPort(addr)
	if err != nil {
		panic(err)
	}
	if listener, ok := listeners[sport]; ok {
		return listener, nil
	}

	return net.Listen("tcp", addr)
}

main.go

package main

import (
	"test/cnet"
	"fmt"
	"log"
	"net/http"
	"os"
)

func main() {

	ln, err := cnet.Listen(":8000")
	if err != nil {
		log.Printf("PID:%d, err:%s\n", os.Getpid(), err.Error())
		os.Exit(1)
	}

	handler := http.NewServeMux()

	handler.HandleFunc("/", func(writer http.ResponseWriter, request *http.Request) {
		str := fmt.Sprintf("systemd socket with go, PID:%d", os.Getpid())

		_, _ = writer.Write([]byte(str))
	})

	srv := http.Server{
		Handler: handler,
	}

	log.Printf("PID: %d, started\n", os.Getpid())
	err = srv.Serve(ln)
	if err != nil {
		log.Printf("PID:%d, err:%s\n", os.Getpid(), err.Error())
	}
}

test@.service

[Unit]
Description=test worker for %i

[Service]
Type=simple
ExecStart=/root/test

[Install]
WantedBy=default.target

test@.socket

[Unit]
Description=test for %i

[Socket]
ListenStream=8000

NoDelay=yes
ReusePort=yes

Service=test@%i.service

[Install]
WantedBy=sockets.target

fail.

The pid output from http does not change