138 lines
3.6 KiB
Go
138 lines
3.6 KiB
Go
package store
|
|
|
|
import (
|
|
"container/list"
|
|
"path"
|
|
"strings"
|
|
"sync/atomic"
|
|
|
|
etcdErr "github.com/coreos/etcd/error"
|
|
)
|
|
|
|
// A watcherHub contains all subscribed watchers
|
|
// watchers is a map with watched path as key and watcher as value
|
|
// EventHistory keeps the old events for watcherHub. It is used to help
|
|
// watcher to get a continuous event history. Or a watcher might miss the
|
|
// event happens between the end of the first watch command and the start
|
|
// of the second command.
|
|
type watcherHub struct {
|
|
watchers map[string]*list.List
|
|
count int64 // current number of watchers.
|
|
EventHistory *EventHistory
|
|
}
|
|
|
|
// newWatchHub creates a watchHub. The capacity determines how many events we will
|
|
// keep in the eventHistory.
|
|
// Typically, we only need to keep a small size of history[smaller than 20K].
|
|
// Ideally, it should smaller than 20K/s[max throughput] * 2 * 50ms[RTT] = 2000
|
|
func newWatchHub(capacity int) *watcherHub {
|
|
return &watcherHub{
|
|
watchers: make(map[string]*list.List),
|
|
EventHistory: newEventHistory(capacity),
|
|
}
|
|
}
|
|
|
|
// watch function returns an Event channel.
|
|
// If recursive is true, the first change after index under key will be sent to the event channel.
|
|
// If recursive is false, the first change after index at key will be sent to the event channel.
|
|
// If index is zero, watch will start from the current index + 1.
|
|
func (wh *watcherHub) watch(key string, recursive bool, index uint64) (<-chan *Event, *etcdErr.Error) {
|
|
event, err := wh.EventHistory.scan(key, recursive, index)
|
|
|
|
if err != nil {
|
|
return nil, err
|
|
}
|
|
|
|
eventChan := make(chan *Event, 1) // use a buffered channel
|
|
|
|
if event != nil {
|
|
eventChan <- event
|
|
|
|
return eventChan, nil
|
|
}
|
|
|
|
w := &watcher{
|
|
eventChan: eventChan,
|
|
recursive: recursive,
|
|
sinceIndex: index,
|
|
}
|
|
|
|
l, ok := wh.watchers[key]
|
|
|
|
if ok { // add the new watcher to the back of the list
|
|
l.PushBack(w)
|
|
|
|
} else { // create a new list and add the new watcher
|
|
l := list.New()
|
|
l.PushBack(w)
|
|
wh.watchers[key] = l
|
|
}
|
|
|
|
atomic.AddInt64(&wh.count, 1)
|
|
|
|
return eventChan, nil
|
|
}
|
|
|
|
// notify function accepts an event and notify to the watchers.
|
|
func (wh *watcherHub) notify(e *Event) {
|
|
e = wh.EventHistory.addEvent(e) // add event into the eventHistory
|
|
|
|
segments := strings.Split(e.Node.Key, "/")
|
|
|
|
currPath := "/"
|
|
|
|
// walk through all the segments of the path and notify the watchers
|
|
// if the path is "/foo/bar", it will notify watchers with path "/",
|
|
// "/foo" and "/foo/bar"
|
|
|
|
for _, segment := range segments {
|
|
currPath = path.Join(currPath, segment)
|
|
// notify the watchers who interests in the changes of current path
|
|
wh.notifyWatchers(e, currPath, false)
|
|
}
|
|
}
|
|
|
|
func (wh *watcherHub) notifyWatchers(e *Event, path string, deleted bool) {
|
|
l, ok := wh.watchers[path]
|
|
if ok {
|
|
curr := l.Front()
|
|
|
|
for {
|
|
if curr == nil { // we have reached the end of the list
|
|
if l.Len() == 0 {
|
|
// if we have notified all watcher in the list
|
|
// we can delete the list
|
|
delete(wh.watchers, path)
|
|
}
|
|
break
|
|
}
|
|
|
|
next := curr.Next() // save reference to the next one in the list
|
|
|
|
w, _ := curr.Value.(*watcher)
|
|
|
|
if w.notify(e, e.Node.Key == path, deleted) {
|
|
|
|
// if we successfully notify a watcher
|
|
// we need to remove the watcher from the list
|
|
// and decrease the counter
|
|
l.Remove(curr)
|
|
atomic.AddInt64(&wh.count, -1)
|
|
|
|
}
|
|
|
|
curr = next // update current to the next
|
|
}
|
|
}
|
|
}
|
|
|
|
// clone function clones the watcherHub and return the cloned one.
|
|
// only clone the static content. do not clone the current watchers.
|
|
func (wh *watcherHub) clone() *watcherHub {
|
|
clonedHistory := wh.EventHistory.clone()
|
|
|
|
return &watcherHub{
|
|
EventHistory: clonedHistory,
|
|
}
|
|
}
|