Server: drop inflight waitgroup (#561)
* Server: drop inflight waitgroup This drops the waitgroup in Server, the suspicion is this can make the server fail to stop; doing this make graceful shutdown not work. Add test that tries to find a race between starting on stopping race; there was a data race on srv.Inflight. The coredns' TestReadme doesn't race anymore with this as it did with the more evasive PR #546.
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@ -525,7 +525,7 @@ func TestTimeout(t *testing.T) {
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length := time.Since(start)
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if length > allowable {
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t.Errorf("exchange took longer (%v) than specified Timeout (%v)", length, timeout)
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t.Errorf("exchange took longer %v than specified Timeout %v", length, allowable)
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}
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}
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29
server.go
29
server.go
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@ -297,10 +297,7 @@ type Server struct {
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// DecorateWriter is optional, allows customization of the process that writes raw DNS messages.
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DecorateWriter DecorateWriter
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// Graceful shutdown handling
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inFlight sync.WaitGroup
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// Shutdown handling
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lock sync.RWMutex
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started bool
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}
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@ -412,10 +409,8 @@ func (srv *Server) ActivateAndServe() error {
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return &Error{err: "bad listeners"}
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}
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// Shutdown gracefully shuts down a server. After a call to Shutdown, ListenAndServe and
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// ActivateAndServe will return. All in progress queries are completed before the server
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// is taken down. If the Shutdown is taking longer than the reading timeout an error
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// is returned.
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// Shutdown shuts down a server. After a call to Shutdown, ListenAndServe and
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// ActivateAndServe will return.
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func (srv *Server) Shutdown() error {
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srv.lock.Lock()
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if !srv.started {
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@ -431,19 +426,7 @@ func (srv *Server) Shutdown() error {
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if srv.Listener != nil {
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srv.Listener.Close()
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}
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fin := make(chan bool)
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go func() {
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srv.inFlight.Wait()
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fin <- true
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}()
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select {
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case <-time.After(srv.getReadTimeout()):
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return &Error{err: "server shutdown is pending"}
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case <-fin:
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return nil
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}
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return nil
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}
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// getReadTimeout is a helper func to use system timeout if server did not intend to change it.
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@ -493,7 +476,6 @@ func (srv *Server) serveTCP(l net.Listener) error {
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if err != nil {
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continue
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}
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srv.inFlight.Add(1)
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go srv.serve(rw.RemoteAddr(), handler, m, nil, nil, rw)
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}
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}
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@ -529,15 +511,12 @@ func (srv *Server) serveUDP(l *net.UDPConn) error {
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if err != nil {
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continue
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}
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srv.inFlight.Add(1)
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go srv.serve(s.RemoteAddr(), handler, m, l, s, nil)
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}
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}
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// Serve a new connection.
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func (srv *Server) serve(a net.Addr, h Handler, m []byte, u *net.UDPConn, s *SessionUDP, t net.Conn) {
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defer srv.inFlight.Done()
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w := &response{tsigSecret: srv.TsigSecret, udp: u, tcp: t, remoteAddr: a, udpSession: s}
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if srv.DecorateWriter != nil {
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w.writer = srv.DecorateWriter(w)
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@ -648,6 +648,22 @@ func TestShutdownUDP(t *testing.T) {
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}
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}
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func TestServerStartStopRace(t *testing.T) {
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for i := 0; i < 10; i++ {
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var err error
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s := &Server{}
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s, _, _, err = RunLocalUDPServerWithFinChan(":0")
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if err != nil {
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t.Fatalf("Could not start server: %s", err)
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}
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go func() {
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if err := s.Shutdown(); err != nil {
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t.Fatalf("Could not stop server: %s", err)
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}
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}()
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}
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}
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type ExampleFrameLengthWriter struct {
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Writer
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}
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