github.com/projectatomic/docker@v1.8.2/daemon/events/events.go (about)

     1  package events
     2  
     3  import (
     4  	"sync"
     5  	"time"
     6  
     7  	"github.com/docker/docker/pkg/jsonmessage"
     8  	"github.com/docker/docker/pkg/pubsub"
     9  )
    10  
    11  const eventsLimit = 64
    12  
    13  // Events is pubsub channel for *jsonmessage.JSONMessage
    14  type Events struct {
    15  	mu     sync.Mutex
    16  	events []*jsonmessage.JSONMessage
    17  	pub    *pubsub.Publisher
    18  }
    19  
    20  // New returns new *Events instance
    21  func New() *Events {
    22  	return &Events{
    23  		events: make([]*jsonmessage.JSONMessage, 0, eventsLimit),
    24  		pub:    pubsub.NewPublisher(100*time.Millisecond, 1024),
    25  	}
    26  }
    27  
    28  // Subscribe adds new listener to events, returns slice of 64 stored last events
    29  // channel in which you can expect new events in form of interface{}, so you
    30  // need type assertion.
    31  func (e *Events) Subscribe() ([]*jsonmessage.JSONMessage, chan interface{}) {
    32  	e.mu.Lock()
    33  	current := make([]*jsonmessage.JSONMessage, len(e.events))
    34  	copy(current, e.events)
    35  	l := e.pub.Subscribe()
    36  	e.mu.Unlock()
    37  	return current, l
    38  }
    39  
    40  // Evict evicts listener from pubsub
    41  func (e *Events) Evict(l chan interface{}) {
    42  	e.pub.Evict(l)
    43  }
    44  
    45  // Log broadcasts event to listeners. Each listener has 100 millisecond for
    46  // receiving event or it will be skipped.
    47  func (e *Events) Log(action, id, from string) {
    48  	go func() {
    49  		e.mu.Lock()
    50  		jm := &jsonmessage.JSONMessage{Status: action, ID: id, From: from, Time: time.Now().UTC().Unix()}
    51  		if len(e.events) == cap(e.events) {
    52  			// discard oldest event
    53  			copy(e.events, e.events[1:])
    54  			e.events[len(e.events)-1] = jm
    55  		} else {
    56  			e.events = append(e.events, jm)
    57  		}
    58  		e.mu.Unlock()
    59  		e.pub.Publish(jm)
    60  	}()
    61  }
    62  
    63  // SubscribersCount returns number of event listeners
    64  func (e *Events) SubscribersCount() int {
    65  	return e.pub.Len()
    66  }