diff --git a/client/internal/peer/notifier.go b/client/internal/peer/notifier.go index ff6a2dd75..1ee1d32ea 100644 --- a/client/internal/peer/notifier.go +++ b/client/internal/peer/notifier.go @@ -5,6 +5,10 @@ import ( ) type notifier struct { + // publishLock orders state publication: it is held across computing the + // effective state and handing it to the listener, so a transition cannot + // overtake a newer one and leave the listener on a stale state. + publishLock sync.Mutex serverStateLock sync.Mutex listenersLock sync.Mutex listener Listener @@ -37,6 +41,9 @@ func (n *notifier) effectiveState(state ClientState) ClientState { // the listener when the flag flips the effective state (Connecting <-> // NoNetwork). func (n *notifier) setNetworkAvailable(available bool) { + n.publishLock.Lock() + defer n.publishLock.Unlock() + n.serverStateLock.Lock() if n.networkAvailable == available { n.serverStateLock.Unlock() @@ -78,6 +85,9 @@ func (n *notifier) removeListener() { } func (n *notifier) updateServerStates(mgmState bool, signalState bool) { + n.publishLock.Lock() + defer n.publishLock.Unlock() + n.serverStateLock.Lock() calculatedState := n.calculateState(mgmState, signalState) @@ -94,6 +104,9 @@ func (n *notifier) updateServerStates(mgmState bool, signalState bool) { } func (n *notifier) clientStart() { + n.publishLock.Lock() + defer n.publishLock.Unlock() + n.serverStateLock.Lock() n.currentClientState = true n.lastNotification = ClientStateConnecting @@ -104,6 +117,9 @@ func (n *notifier) clientStart() { } func (n *notifier) clientStop() { + n.publishLock.Lock() + defer n.publishLock.Unlock() + n.serverStateLock.Lock() n.currentClientState = false n.lastNotification = ClientStateDisconnected @@ -113,6 +129,9 @@ func (n *notifier) clientStop() { } func (n *notifier) clientTearDown() { + n.publishLock.Lock() + defer n.publishLock.Unlock() + n.serverStateLock.Lock() n.currentClientState = false n.lastNotification = ClientStateDisconnecting diff --git a/client/internal/peer/notifier_concurrent_test.go b/client/internal/peer/notifier_concurrent_test.go new file mode 100644 index 000000000..fcaaaad3b --- /dev/null +++ b/client/internal/peer/notifier_concurrent_test.go @@ -0,0 +1,108 @@ +package peer + +import ( + "sync" + "testing" + "time" +) + +type recordingListener struct { + mu sync.Mutex + states []ClientState + onState func(ClientState) +} + +func (l *recordingListener) OnStateChanged(state ClientState) { + l.mu.Lock() + l.states = append(l.states, state) + hook := l.onState + l.mu.Unlock() + + if hook != nil { + hook(state) + } +} + +func (l *recordingListener) last() (ClientState, bool) { + l.mu.Lock() + defer l.mu.Unlock() + if len(l.states) == 0 { + return 0, false + } + return l.states[len(l.states)-1], true +} + +func (l *recordingListener) snapshot() []ClientState { + l.mu.Lock() + defer l.mu.Unlock() + return append([]ClientState(nil), l.states...) +} + +func (l *recordingListener) OnConnected() {} +func (l *recordingListener) OnDisconnected() {} +func (l *recordingListener) OnConnecting() {} +func (l *recordingListener) OnDisconnecting() {} +func (l *recordingListener) OnAddressChanged(string, string) {} +func (l *recordingListener) OnPeersListChanged(int) {} + +// TestNotifier_ConcurrentAvailabilityFlipOrdersPublication holds the first +// transition inside the listener callback and flips availability again from +// another goroutine while it is parked. The second flip must not publish +// ahead of the one in flight, otherwise the listener ends up on a state the +// notifier already superseded. +func TestNotifier_ConcurrentAvailabilityFlipOrdersPublication(t *testing.T) { + n := newNotifier() + n.currentClientState = true + n.lastNotification = ClientStateConnecting + + entered := make(chan struct{}) + release := make(chan struct{}) + + l := &recordingListener{} + l.onState = func(state ClientState) { + if state != ClientStateNoNetwork { + return + } + l.mu.Lock() + l.onState = nil + l.mu.Unlock() + close(entered) + <-release + } + n.listener = l + + var wg sync.WaitGroup + wg.Add(1) + go func() { + defer wg.Done() + n.setNetworkAvailable(false) + }() + + <-entered + + flipped := make(chan struct{}) + go func() { + defer close(flipped) + n.setNetworkAvailable(true) + }() + + select { + case <-flipped: + t.Fatal("the online transition published while the offline one was " + + "still in flight; publication is not serialized") + case <-time.After(200 * time.Millisecond): + } + + close(release) + <-flipped + wg.Wait() + + got, ok := l.last() + if !ok { + t.Fatal("listener never observed a state") + } + if got != ClientStateConnecting { + t.Fatalf("listener holds %v after the network came back, want Connecting; sequence: %v", + got, l.snapshot()) + } +}