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moby--moby/daemon/events/events.go

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package events
import (
"sync"
"time"
"github.com/docker/docker/pkg/jsonmessage"
"github.com/docker/docker/pkg/pubsub"
)
const (
eventsLimit = 64
bufferSize = 1024
)
// Events is pubsub channel for *jsonmessage.JSONMessage
type Events struct {
mu sync.Mutex
events []*jsonmessage.JSONMessage
pub *pubsub.Publisher
}
// New returns new *Events instance
func New() *Events {
return &Events{
events: make([]*jsonmessage.JSONMessage, 0, eventsLimit),
pub: pubsub.NewPublisher(100*time.Millisecond, bufferSize),
}
}
// Subscribe 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), and a function to call
// to stop the stream of events.
func (e *Events) Subscribe() ([]*jsonmessage.JSONMessage, chan interface{}, func()) {
e.mu.Lock()
current := make([]*jsonmessage.JSONMessage, len(e.events))
copy(current, e.events)
l := e.pub.Subscribe()
e.mu.Unlock()
cancel := func() {
e.Evict(l)
}
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)
}
// Log broadcasts event to listeners. Each listener has 100 millisecond for
// receiving event or it will be skipped.
func (e *Events) Log(action, id, from string) {
now := time.Now().UTC()
jm := &jsonmessage.JSONMessage{Status: action, ID: id, From: from, Time: now.Unix(), TimeNano: now.UnixNano()}
e.mu.Lock()
if len(e.events) == cap(e.events) {
// discard oldest event
copy(e.events, e.events[1:])
e.events[len(e.events)-1] = jm
} else {
e.events = append(e.events, jm)
}
e.mu.Unlock()
e.pub.Publish(jm)
}
// SubscribersCount returns number of event listeners
func (e *Events) SubscribersCount() int {
return e.pub.Len()
}