| // Copyright 2015 The etcd Authors |
| // |
| // Licensed under the Apache License, Version 2.0 (the "License"); |
| // you may not use this file except in compliance with the License. |
| // You may obtain a copy of the License at |
| // |
| // http://www.apache.org/licenses/LICENSE-2.0 |
| // |
| // Unless required by applicable law or agreed to in writing, software |
| // distributed under the License is distributed on an "AS IS" BASIS, |
| // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| // See the License for the specific language governing permissions and |
| // limitations under the License. |
| |
| package v2store |
| |
| import ( |
| "container/list" |
| "path" |
| "strings" |
| "sync" |
| "sync/atomic" |
| |
| "go.etcd.io/etcd/etcdserver/api/v2error" |
| ) |
| |
| // 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 { |
| // count must be the first element to keep 64-bit alignment for atomic |
| // access |
| |
| count int64 // current number of watchers. |
| |
| mutex sync.Mutex |
| watchers map[string]*list.List |
| EventHistory *EventHistory |
| } |
| |
| // newWatchHub creates a watcherHub. 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 a Watcher. |
| // If recursive is true, the first change after index under key will be sent to the event channel of the watcher. |
| // If recursive is false, the first change after index at key will be sent to the event channel of the watcher. |
| // If index is zero, watch will start from the current index + 1. |
| func (wh *watcherHub) watch(key string, recursive, stream bool, index, storeIndex uint64) (Watcher, *v2error.Error) { |
| reportWatchRequest() |
| event, err := wh.EventHistory.scan(key, recursive, index) |
| |
| if err != nil { |
| err.Index = storeIndex |
| return nil, err |
| } |
| |
| w := &watcher{ |
| eventChan: make(chan *Event, 100), // use a buffered channel |
| recursive: recursive, |
| stream: stream, |
| sinceIndex: index, |
| startIndex: storeIndex, |
| hub: wh, |
| } |
| |
| wh.mutex.Lock() |
| defer wh.mutex.Unlock() |
| // If the event exists in the known history, append the EtcdIndex and return immediately |
| if event != nil { |
| ne := event.Clone() |
| ne.EtcdIndex = storeIndex |
| w.eventChan <- ne |
| return w, nil |
| } |
| |
| l, ok := wh.watchers[key] |
| |
| var elem *list.Element |
| |
| if ok { // add the new watcher to the back of the list |
| elem = l.PushBack(w) |
| } else { // create a new list and add the new watcher |
| l = list.New() |
| elem = l.PushBack(w) |
| wh.watchers[key] = l |
| } |
| |
| w.remove = func() { |
| if w.removed { // avoid removing it twice |
| return |
| } |
| w.removed = true |
| l.Remove(elem) |
| atomic.AddInt64(&wh.count, -1) |
| reportWatcherRemoved() |
| if l.Len() == 0 { |
| delete(wh.watchers, key) |
| } |
| } |
| |
| atomic.AddInt64(&wh.count, 1) |
| reportWatcherAdded() |
| |
| return w, nil |
| } |
| |
| func (wh *watcherHub) add(e *Event) { |
| wh.EventHistory.addEvent(e) |
| } |
| |
| // 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, nodePath string, deleted bool) { |
| wh.mutex.Lock() |
| defer wh.mutex.Unlock() |
| |
| l, ok := wh.watchers[nodePath] |
| if ok { |
| curr := l.Front() |
| |
| for curr != nil { |
| next := curr.Next() // save reference to the next one in the list |
| |
| w, _ := curr.Value.(*watcher) |
| |
| originalPath := e.Node.Key == nodePath |
| if (originalPath || !isHidden(nodePath, e.Node.Key)) && w.notify(e, originalPath, deleted) { |
| if !w.stream { // do not remove the stream watcher |
| // if we successfully notify a watcher |
| // we need to remove the watcher from the list |
| // and decrease the counter |
| w.removed = true |
| l.Remove(curr) |
| atomic.AddInt64(&wh.count, -1) |
| reportWatcherRemoved() |
| } |
| } |
| |
| curr = next // update current to the next element in the list |
| } |
| |
| if l.Len() == 0 { |
| // if we have notified all watcher in the list |
| // we can delete the list |
| delete(wh.watchers, nodePath) |
| } |
| } |
| } |
| |
| // 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, |
| } |
| } |
| |
| // isHidden checks to see if key path is considered hidden to watch path i.e. the |
| // last element is hidden or it's within a hidden directory |
| func isHidden(watchPath, keyPath string) bool { |
| // When deleting a directory, watchPath might be deeper than the actual keyPath |
| // For example, when deleting /foo we also need to notify watchers on /foo/bar. |
| if len(watchPath) > len(keyPath) { |
| return false |
| } |
| // if watch path is just a "/", after path will start without "/" |
| // add a "/" to deal with the special case when watchPath is "/" |
| afterPath := path.Clean("/" + keyPath[len(watchPath):]) |
| return strings.Contains(afterPath, "/_") |
| } |