hanayo/vendor/github.com/rcrowley/goagain/example/double/main.go
2019-02-23 13:29:15 +00:00

106 lines
2.3 KiB
Go

package main
import (
"github.com/rcrowley/goagain"
"fmt"
"log"
"net"
"sync"
"syscall"
"time"
)
func init() {
goagain.Strategy = goagain.Double
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.
ch := make(chan struct{})
wg := &sync.WaitGroup{}
wg.Add(1)
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, ch, wg)
} else {
// Resume listening and accepting connections in a new goroutine.
log.Println("resuming listening on", l.Addr())
go serve(l, ch, wg)
// If this is the child, send the parent SIGUSR2. If this is the
// parent, send the child SIGQUIT.
if err := goagain.Kill(); nil != err {
log.Fatalln(err)
}
}
// Block the main goroutine awaiting signals.
sig, err := goagain.Wait(l)
if 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 close the channel to signal the goroutine to stop
// accepting connections and wait for the goroutine to exit.
close(ch)
wg.Wait()
// If we received SIGUSR2, re-exec the parent process.
if goagain.SIGUSR2 == sig {
if err := goagain.Exec(l); nil != err {
log.Fatalln(err)
}
}
}
// A very rude server that says hello and then closes your connection.
func serve(l net.Listener, ch chan struct{}, wg *sync.WaitGroup) {
defer wg.Done()
for {
// Break out of the accept loop on the next iteration after the
// process was signaled and our channel was closed.
select {
case <-ch:
return
default:
}
// Set a deadline so Accept doesn't block forever, which gives
// us an opportunity to stop gracefully.
l.(*net.TCPListener).SetDeadline(time.Now().Add(100e6))
c, err := l.Accept()
if nil != err {
if goagain.IsErrClosing(err) {
return
}
if err.(*net.OpError).Timeout() {
continue
}
log.Fatalln(err)
}
c.Write([]byte("Hello, world!\n"))
c.Close()
}
}