95 lines
2.0 KiB
Go
95 lines
2.0 KiB
Go
// ## HTTP Serve Graceful Shutdown
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package main
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import (
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"net"
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"net/http"
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"time"
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"os"
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"os/signal"
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"syscall"
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"fmt"
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"sync/atomic"
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)
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func slow(res http.ResponseWriter, req *http.Request) {
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fmt.Println("respond at=start")
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time.Sleep(time.Second * 5)
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res.Header().Set("Content-Type", "text/plain")
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fmt.Fprintln(res, "Finally.")
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fmt.Println("respond at=finish")
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}
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var connCount int64 = 0
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type watchedConn struct {
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net.Conn
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}
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func (w *watchedConn) Close() error {
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atomic.AddInt64(&connCount, -1)
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return w.Conn.Close()
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}
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type watchedListener struct {
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net.Listener
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}
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func (l *watchedListener) Accept() (net.Conn, error) {
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conn, err := l.Listener.Accept()
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if err != nil {
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return nil, err
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}
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atomic.AddInt64(&connCount, 1)
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return &watchedConn{Conn: conn}, nil
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}
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func main() {
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stop := make(chan bool, 1)
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sig := make(chan os.Signal, 1)
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server := &http.Server{Handler: http.HandlerFunc(slow)}
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fmt.Println("listen at=start")
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listener, listenErr := net.Listen("tcp", ":5000")
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if listenErr != nil { panic(listenErr) }
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wListener := &watchedListener{Listener: listener}
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fmt.Println("listen at=finish")
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go func() {
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<- stop
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fmt.Println("close at=start")
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closeErr := wListener.Close()
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if closeErr != nil { panic(closeErr) }
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fmt.Println("close at=finish")
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}()
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go func() {
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signal.Notify(sig, syscall.SIGINT, syscall.SIGTERM)
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fmt.Println("trap at=start")
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<- sig
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stop <- true
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fmt.Println("trap at=finish")
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}()
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fmt.Println("serve at=start")
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server.Serve(wListener)
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fmt.Println("serve at=finish")
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for {
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connCountCurrent := atomic.LoadInt64(&connCount)
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if connCountCurrent > 0 {
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fmt.Println("wait at=pending remaining=", connCountCurrent)
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time.Sleep(time.Second)
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} else {
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fmt.Println("wait at=finish remaining=", connCountCurrent)
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return
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}
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}
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}
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// todo: clean up logging
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// todo: limit shutdown time
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// todo: factor out to cut-and-pastable against normal app
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// todo: credit http://blog.nella.org/?p=879
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// todo: comment about tcp servers
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