96 lines
3.2 KiB
Go
96 lines
3.2 KiB
Go
// Copyright 2015 The etcd Authors
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package v2store
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type Watcher interface {
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EventChan() chan *Event
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StartIndex() uint64 // The EtcdIndex at which the Watcher was created
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Remove()
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}
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type watcher struct {
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eventChan chan *Event
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stream bool
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recursive bool
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sinceIndex uint64
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startIndex uint64
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hub *watcherHub
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removed bool
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remove func()
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}
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func (w *watcher) EventChan() chan *Event {
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return w.eventChan
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}
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func (w *watcher) StartIndex() uint64 {
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return w.startIndex
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}
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// notify function notifies the watcher. If the watcher interests in the given path,
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// the function will return true.
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func (w *watcher) notify(e *Event, originalPath bool, deleted bool) bool {
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// watcher is interested the path in three cases and under one condition
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// the condition is that the event happens after the watcher's sinceIndex
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// 1. the path at which the event happens is the path the watcher is watching at.
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// For example if the watcher is watching at "/foo" and the event happens at "/foo",
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// the watcher must be interested in that event.
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// 2. the watcher is a recursive watcher, it interests in the event happens after
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// its watching path. For example if watcher A watches at "/foo" and it is a recursive
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// one, it will interest in the event happens at "/foo/bar".
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// 3. when we delete a directory, we need to force notify all the watchers who watches
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// at the file we need to delete.
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// For example a watcher is watching at "/foo/bar". And we deletes "/foo". The watcher
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// should get notified even if "/foo" is not the path it is watching.
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if (w.recursive || originalPath || deleted) && e.Index() >= w.sinceIndex {
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// We cannot block here if the eventChan capacity is full, otherwise
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// etcd will hang. eventChan capacity is full when the rate of
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// notifications are higher than our send rate.
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// If this happens, we close the channel.
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select {
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case w.eventChan <- e:
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default:
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// We have missed a notification. Remove the watcher.
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// Removing the watcher also closes the eventChan.
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w.remove()
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}
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return true
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}
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return false
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}
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// Remove removes the watcher from watcherHub
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// The actual remove function is guaranteed to only be executed once
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func (w *watcher) Remove() {
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w.hub.mutex.Lock()
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defer w.hub.mutex.Unlock()
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close(w.eventChan)
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if w.remove != nil {
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w.remove()
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}
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}
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// nopWatcher is a watcher that receives nothing, always blocking.
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type nopWatcher struct{}
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func NewNopWatcher() Watcher { return &nopWatcher{} }
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func (w *nopWatcher) EventChan() chan *Event { return nil }
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func (w *nopWatcher) StartIndex() uint64 { return 0 }
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func (w *nopWatcher) Remove() {}
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