Add PubSub topics.

A TopicFunc is an interface to let the pubisher decide whether it needs
to send a message to a subscriber or not. It returns true if the
publisher must send the message and false otherwise.

Users of the pubsub package can create a subscriber with a topic
function by calling `pubsub.SubscribeTopic`.

Message delivery has also been modified to use concurrent channels per
subscriber. That way, topic verification and message delivery is not
o(N+M) anymore, based on the number of subscribers and topic verification
complexity.

Using pubsub topics, the API stops controlling the message delivery,
delegating that function to a topic generated with the filtering
provided by the user. The publisher sends every message to the
subscriber if there is no filter, but the api doesn't have to select
messages to return anymore.

Signed-off-by: David Calavera <david.calavera@gmail.com>

api/server/router/local/info.go

@@ -92,30 +92,14 @@ func (s *router) getEvents(ctx context.Context, w http.ResponseWriter, r *http.R
 
 	enc := json.NewEncoder(output)
 
-	current, l, cancel := s.daemon.SubscribeToEvents()
-	defer cancel()
+	buffered, l := s.daemon.SubscribeToEvents(since, sinceNano, ef)
+	defer s.daemon.UnsubscribeFromEvents(l)
 
-	eventFilter := s.daemon.GetEventFilter(ef)
-	handleEvent := func(ev *jsonmessage.JSONMessage) error {
-		if eventFilter.Include(ev) {
+	for _, ev := range buffered {
 		if err := enc.Encode(ev); err != nil {
 			return err
 		}
 	}
-		return nil
-	}
-
-	if since == -1 {
-		current = nil
-	}
-	for _, ev := range current {
-		if ev.Time < since || ((ev.Time == since) && (ev.TimeNano < sinceNano)) {
-			continue
-		}
-		if err := handleEvent(ev); err != nil {
-			return err
-		}
-	}
 
 	var closeNotify <-chan bool
 	if closeNotifier, ok := w.(http.CloseNotifier); ok {
@@ -129,7 +113,7 @@ func (s *router) getEvents(ctx context.Context, w http.ResponseWriter, r *http.R
 			if !ok {
 				continue
 			}
-			if err := handleEvent(jev); err != nil {
+			if err := enc.Encode(jev); err != nil {
 				return err
 			}
 		case <-timer.C:

daemon/daemon.go

@@ -532,8 +532,8 @@ func (daemon *Daemon) GetByName(name string) (*Container, error) {
 	return e, nil
 }
 
-// GetEventFilter returns a filters.Filter for a set of filters
-func (daemon *Daemon) GetEventFilter(filter filters.Args) *events.Filter {
+// getEventFilter returns a filters.Filter for a set of filters
+func (daemon *Daemon) getEventFilter(filter filters.Args) *events.Filter {
 	// incoming container filter can be name, id or partial id, convert to
 	// a full container id
 	for _, cn := range filter.Get("container") {
@@ -547,8 +547,15 @@ func (daemon *Daemon) GetEventFilter(filter filters.Args) *events.Filter {
 }
 
 // SubscribeToEvents returns the currently record of events, a channel to stream new events from, and a function to cancel the stream of events.
-func (daemon *Daemon) SubscribeToEvents() ([]*jsonmessage.JSONMessage, chan interface{}, func()) {
-	return daemon.EventsService.Subscribe()
+func (daemon *Daemon) SubscribeToEvents(since, sinceNano int64, filter filters.Args) ([]*jsonmessage.JSONMessage, chan interface{}) {
+	ef := daemon.getEventFilter(filter)
+	return daemon.EventsService.SubscribeTopic(since, sinceNano, ef)
+}
+
+// UnsubscribeFromEvents stops the event subscription for a client by closing the
+// channel where the daemon sends events to.
+func (daemon *Daemon) UnsubscribeFromEvents(listener chan interface{}) {
+	daemon.EventsService.Evict(listener)
 }
 
 // GetLabels for a container or image id

daemon/events/events.go

@@ -8,7 +8,10 @@ import (
 	"github.com/docker/docker/pkg/pubsub"
 )
 
-const eventsLimit = 64
+const (
+	eventsLimit = 64
+	bufferSize  = 1024
+)
 
 // Events is pubsub channel for *jsonmessage.JSONMessage
 type Events struct {
@@ -21,7 +24,7 @@ type Events struct {
 func New() *Events {
 	return &Events{
 		events: make([]*jsonmessage.JSONMessage, 0, eventsLimit),
-		pub:    pubsub.NewPublisher(100*time.Millisecond, 1024),
+		pub:    pubsub.NewPublisher(100*time.Millisecond, bufferSize),
 	}
 }
 
@@ -42,6 +45,41 @@ func (e *Events) Subscribe() ([]*jsonmessage.JSONMessage, chan interface{}, func
 	return current, l, cancel
 }
 
+// SubscribeTopic adds new listener to events, returns slice of 64 stored
+// last events, a channel in which you can expect new events (in form
+// of interface{}, so you need type assertion).
+func (e *Events) SubscribeTopic(since, sinceNano int64, ef *Filter) ([]*jsonmessage.JSONMessage, chan interface{}) {
+	e.mu.Lock()
+	defer e.mu.Unlock()
+
+	var buffered []*jsonmessage.JSONMessage
+	topic := func(m interface{}) bool {
+		return ef.Include(m.(*jsonmessage.JSONMessage))
+	}
+
+	if since != -1 {
+		for i := len(e.events) - 1; i >= 0; i-- {
+			ev := e.events[i]
+			if ev.Time < since || ((ev.Time == since) && (ev.TimeNano < sinceNano)) {
+				break
+			}
+			if ef.filter.Len() == 0 || topic(ev) {
+				buffered = append([]*jsonmessage.JSONMessage{ev}, buffered...)
+			}
+		}
+	}
+
+	var ch chan interface{}
+	if ef.filter.Len() > 0 {
+		ch = e.pub.SubscribeTopic(topic)
+	} else {
+		// Subscribe to all events if there are no filters
+		ch = e.pub.Subscribe()
+	}
+
+	return buffered, ch
+}
+
 // Evict evicts listener from pubsub
 func (e *Events) Evict(l chan interface{}) {
 	e.pub.Evict(l)

integration-cli/docker_cli_build_test.go

@@ -1891,9 +1891,7 @@ func (s *DockerSuite) TestBuildCancellationKillsSleep(c *check.C) {
 
 	startEpoch := daemonTime(c).Unix()
 	// Watch for events since epoch.
-	eventsCmd := exec.Command(
-		dockerBinary, "events",
-		"--since", strconv.FormatInt(startEpoch, 10))
+	eventsCmd := exec.Command(dockerBinary, "events", "--since", strconv.FormatInt(startEpoch, 10))
 	stdout, err := eventsCmd.StdoutPipe()
 	if err != nil {
 		c.Fatal(err)
@@ -1932,12 +1930,12 @@ func (s *DockerSuite) TestBuildCancellationKillsSleep(c *check.C) {
 		c.Fatalf("failed to run build: %s", err)
 	}
 
-	matchCID := regexp.MustCompile("Running in ")
+	matchCID := regexp.MustCompile("Running in (.+)")
 	scanner := bufio.NewScanner(stdoutBuild)
 	for scanner.Scan() {
 		line := scanner.Text()
-		if ok := matchCID.MatchString(line); ok {
-			containerID <- line[len(line)-12:]
+		if matches := matchCID.FindStringSubmatch(line); len(matches) > 0 {
+			containerID <- matches[1]
 			break
 		}
 	}

pkg/pubsub/publisher.go

@@ -13,11 +13,12 @@ func NewPublisher(publishTimeout time.Duration, buffer int) *Publisher {
 	return &Publisher{
 		buffer:      buffer,
 		timeout:     publishTimeout,
-		subscribers: make(map[subscriber]struct{}),
+		subscribers: make(map[subscriber]topicFunc),
 	}
 }
 
 type subscriber chan interface{}
+type topicFunc func(v interface{}) bool
 
 // Publisher is basic pub/sub structure. Allows to send events and subscribe
 // to them. Can be safely used from multiple goroutines.
@@ -25,7 +26,7 @@ type Publisher struct {
 	m           sync.RWMutex
 	buffer      int
 	timeout     time.Duration
-	subscribers map[subscriber]struct{}
+	subscribers map[subscriber]topicFunc
 }
 
 // Len returns the number of subscribers for the publisher
@@ -38,9 +39,14 @@ func (p *Publisher) Len() int {
 
 // Subscribe adds a new subscriber to the publisher returning the channel.
 func (p *Publisher) Subscribe() chan interface{} {
+	return p.SubscribeTopic(nil)
+}
+
+// SubscribeTopic adds a new subscriber that filters messages sent by a topic.
+func (p *Publisher) SubscribeTopic(topic topicFunc) chan interface{} {
 	ch := make(chan interface{}, p.buffer)
 	p.m.Lock()
-	p.subscribers[ch] = struct{}{}
+	p.subscribers[ch] = topic
 	p.m.Unlock()
 	return ch
 }
@@ -56,20 +62,13 @@ func (p *Publisher) Evict(sub chan interface{}) {
 // Publish sends the data in v to all subscribers currently registered with the publisher.
 func (p *Publisher) Publish(v interface{}) {
 	p.m.RLock()
-	for sub := range p.subscribers {
-		// send under a select as to not block if the receiver is unavailable
-		if p.timeout > 0 {
-			select {
-			case sub <- v:
-			case <-time.After(p.timeout):
-			}
-			continue
-		}
-		select {
-		case sub <- v:
-		default:
-		}
+	wg := new(sync.WaitGroup)
+	for sub, topic := range p.subscribers {
+		wg.Add(1)
+
+		go p.sendTopic(sub, topic, v, wg)
 	}
+	wg.Wait()
 	p.m.RUnlock()
 }
 
@@ -82,3 +81,24 @@ func (p *Publisher) Close() {
 	}
 	p.m.Unlock()
 }
+
+func (p *Publisher) sendTopic(sub subscriber, topic topicFunc, v interface{}, wg *sync.WaitGroup) {
+	defer wg.Done()
+	if topic != nil && !topic(v) {
+		return
+	}
+
+	// send under a select as to not block if the receiver is unavailable
+	if p.timeout > 0 {
+		select {
+		case sub <- v:
+		case <-time.After(p.timeout):
+		}
+		return
+	}
+
+	select {
+	case sub <- v:
+	default:
+	}
+}