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package main
import (
"github.com/rcrowley/goagain"
"fmt"
"log"
"net"
"syscall"
"time"
)
func init() {
log.SetFlags(log.Lmicroseconds | log.Lshortfile)
log.SetPrefix(fmt.Sprintf("pid:%d ", syscall.Getpid()))
}
func main() {
// Inherit a net.Listener from our parent process or listen anew.
l, err := goagain.Listener()
if nil != err {
// Listen on a TCP or a UNIX domain socket (TCP here).
l, err = net.Listen("tcp", "127.0.0.1:48879")
if nil != err {
log.Fatalln(err)
}
log.Println("listening on", l.Addr())
// Accept connections in a new goroutine.
go serve(l)
} else {
// Resume accepting connections in a new goroutine.
log.Println("resuming listening on", l.Addr())
go serve(l)
// Kill the parent, now that the child has started successfully.
if err := goagain.Kill(); nil != err {
log.Fatalln(err)
}
}
// Block the main goroutine awaiting signals.
if _, err := goagain.Wait(l); nil != err {
log.Fatalln(err)
}
// Do whatever's necessary to ensure a graceful exit like waiting for
// goroutines to terminate or a channel to become closed.
//
// In this case, we'll simply stop listening and wait one second.
if err := l.Close(); nil != err {
log.Fatalln(err)
}
time.Sleep(1e9)
}
// A very rude server that says hello and then closes your connection.
func serve(l net.Listener) {
for {
c, err := l.Accept()
if nil != err {
if goagain.IsErrClosing(err) {
break
}
log.Fatalln(err)
}
c.Write([]byte("Hello, world!\n"))
c.Close()
}
}