| // 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 |
| |
| type Watcher interface { |
| EventChan() chan *Event |
| StartIndex() uint64 // The EtcdIndex at which the Watcher was created |
| Remove() |
| } |
| |
| type watcher struct { |
| eventChan chan *Event |
| stream bool |
| recursive bool |
| sinceIndex uint64 |
| startIndex uint64 |
| hub *watcherHub |
| removed bool |
| remove func() |
| } |
| |
| func (w *watcher) EventChan() chan *Event { |
| return w.eventChan |
| } |
| |
| func (w *watcher) StartIndex() uint64 { |
| return w.startIndex |
| } |
| |
| // notify function notifies the watcher. If the watcher interests in the given path, |
| // the function will return true. |
| func (w *watcher) notify(e *Event, originalPath bool, deleted bool) bool { |
| // watcher is interested the path in three cases and under one condition |
| // the condition is that the event happens after the watcher's sinceIndex |
| |
| // 1. the path at which the event happens is the path the watcher is watching at. |
| // For example if the watcher is watching at "/foo" and the event happens at "/foo", |
| // the watcher must be interested in that event. |
| |
| // 2. the watcher is a recursive watcher, it interests in the event happens after |
| // its watching path. For example if watcher A watches at "/foo" and it is a recursive |
| // one, it will interest in the event happens at "/foo/bar". |
| |
| // 3. when we delete a directory, we need to force notify all the watchers who watches |
| // at the file we need to delete. |
| // For example a watcher is watching at "/foo/bar". And we deletes "/foo". The watcher |
| // should get notified even if "/foo" is not the path it is watching. |
| if (w.recursive || originalPath || deleted) && e.Index() >= w.sinceIndex { |
| // We cannot block here if the eventChan capacity is full, otherwise |
| // etcd will hang. eventChan capacity is full when the rate of |
| // notifications are higher than our send rate. |
| // If this happens, we close the channel. |
| select { |
| case w.eventChan <- e: |
| default: |
| // We have missed a notification. Remove the watcher. |
| // Removing the watcher also closes the eventChan. |
| w.remove() |
| } |
| return true |
| } |
| return false |
| } |
| |
| // Remove removes the watcher from watcherHub |
| // The actual remove function is guaranteed to only be executed once |
| func (w *watcher) Remove() { |
| w.hub.mutex.Lock() |
| defer w.hub.mutex.Unlock() |
| |
| close(w.eventChan) |
| if w.remove != nil { |
| w.remove() |
| } |
| } |
| |
| // nopWatcher is a watcher that receives nothing, always blocking. |
| type nopWatcher struct{} |
| |
| func NewNopWatcher() Watcher { return &nopWatcher{} } |
| func (w *nopWatcher) EventChan() chan *Event { return nil } |
| func (w *nopWatcher) StartIndex() uint64 { return 0 } |
| func (w *nopWatcher) Remove() {} |