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moby--moby/events/events.go

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package events
import (
"encoding/json"
"sync"
"time"
"github.com/docker/docker/engine"
"github.com/docker/docker/pkg/parsers/filters"
"github.com/docker/docker/utils"
)
const eventsLimit = 64
type listener chan<- *utils.JSONMessage
type Events struct {
mu sync.RWMutex
events []*utils.JSONMessage
subscribers []listener
}
func New() *Events {
return &Events{
events: make([]*utils.JSONMessage, 0, eventsLimit),
}
}
// Install installs events public api in docker engine
func (e *Events) Install(eng *engine.Engine) error {
// Here you should describe public interface
jobs := map[string]engine.Handler{
"events": e.Get,
"log": e.Log,
"subscribers_count": e.SubscribersCount,
}
for name, job := range jobs {
if err := eng.Register(name, job); err != nil {
return err
}
}
return nil
}
func (e *Events) Get(job *engine.Job) engine.Status {
var (
since = job.GetenvInt64("since")
until = job.GetenvInt64("until")
timeout = time.NewTimer(time.Unix(until, 0).Sub(time.Now()))
)
eventFilters, err := filters.FromParam(job.Getenv("filters"))
if err != nil {
return job.Error(err)
}
// If no until, disable timeout
if until == 0 {
timeout.Stop()
}
listener := make(chan *utils.JSONMessage)
e.subscribe(listener)
defer e.unsubscribe(listener)
job.Stdout.Write(nil)
// Resend every event in the [since, until] time interval.
if since != 0 {
if err := e.writeCurrent(job, since, until, eventFilters); err != nil {
return job.Error(err)
}
}
for {
select {
case event, ok := <-listener:
if !ok {
return engine.StatusOK
}
if err := writeEvent(job, event, eventFilters); err != nil {
return job.Error(err)
}
case <-timeout.C:
return engine.StatusOK
}
}
}
func (e *Events) Log(job *engine.Job) engine.Status {
if len(job.Args) != 3 {
return job.Errorf("usage: %s ACTION ID FROM", job.Name)
}
// not waiting for receivers
go e.log(job.Args[0], job.Args[1], job.Args[2])
return engine.StatusOK
}
func (e *Events) SubscribersCount(job *engine.Job) engine.Status {
ret := &engine.Env{}
ret.SetInt("count", e.subscribersCount())
ret.WriteTo(job.Stdout)
return engine.StatusOK
}
func writeEvent(job *engine.Job, event *utils.JSONMessage, eventFilters filters.Args) error {
isFiltered := func(field string, filter []string) bool {
if len(filter) == 0 {
return false
}
for _, v := range filter {
if v == field {
return false
}
}
return true
}
if isFiltered(event.Status, eventFilters["event"]) || isFiltered(event.From, eventFilters["image"]) || isFiltered(event.ID, eventFilters["container"]) {
return nil
}
// When sending an event JSON serialization errors are ignored, but all
// other errors lead to the eviction of the listener.
if b, err := json.Marshal(event); err == nil {
if _, err = job.Stdout.Write(b); err != nil {
return err
}
}
return nil
}
func (e *Events) writeCurrent(job *engine.Job, since, until int64, eventFilters filters.Args) error {
e.mu.RLock()
for _, event := range e.events {
if event.Time >= since && (event.Time <= until || until == 0) {
if err := writeEvent(job, event, eventFilters); err != nil {
e.mu.RUnlock()
return err
}
}
}
e.mu.RUnlock()
return nil
}
func (e *Events) subscribersCount() int {
e.mu.RLock()
c := len(e.subscribers)
e.mu.RUnlock()
return c
}
func (e *Events) log(action, id, from string) {
e.mu.Lock()
now := time.Now().UTC().Unix()
jm := &utils.JSONMessage{Status: action, ID: id, From: from, Time: now}
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)
}
for _, s := range e.subscribers {
// We give each subscriber a 100ms time window to receive the event,
// after which we move to the next.
select {
case s <- jm:
case <-time.After(100 * time.Millisecond):
}
}
e.mu.Unlock()
}
func (e *Events) subscribe(l listener) {
e.mu.Lock()
e.subscribers = append(e.subscribers, l)
e.mu.Unlock()
}
// unsubscribe closes and removes the specified listener from the list of
// previously registed ones.
// It returns a boolean value indicating if the listener was successfully
// found, closed and unregistered.
func (e *Events) unsubscribe(l listener) bool {
e.mu.Lock()
for i, subscriber := range e.subscribers {
if subscriber == l {
close(l)
e.subscribers = append(e.subscribers[:i], e.subscribers[i+1:]...)
e.mu.Unlock()
return true
}
}
e.mu.Unlock()
return false
}