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https://github.com/etcd-io/etcd.git
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deb1da5f57
One watcher includes multiple watchings, and their events are sent out through one channel. For the received event, user would like to know which watching it belongs to. Introduce a watch ID. When watching on some key, user will get a watch ID. The watch ID is attached to all events that is observed by this watch.
85 lines
2.4 KiB
Go
85 lines
2.4 KiB
Go
// Copyright 2015 CoreOS, Inc.
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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 storage
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import (
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"sync"
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"github.com/coreos/etcd/storage/storagepb"
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)
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type Watcher interface {
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// Watch watches the events happening or happened on the given key
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// or key prefix from the given startRev.
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// The whole event history can be watched unless compacted.
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// If `prefix` is true, watch observes all events whose key prefix could be the given `key`.
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// If `startRev` <=0, watch observes events after currentRev.
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// The returned `id` is the ID of this watching. It appears as WatchID
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// in events that are sent to this watching.
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Watch(key []byte, prefix bool, startRev int64) (id int64, cancel CancelFunc)
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// Chan returns a chan. All watched events will be sent to the returned chan.
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Chan() <-chan storagepb.Event
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// Close closes the WatchChan and release all related resources.
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Close()
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}
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// watcher contains a collection of watching that share
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// one chan to send out watched events and other control events.
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type watcher struct {
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watchable watchable
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ch chan storagepb.Event
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mu sync.Mutex // guards fields below it
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nextID int64 // nextID is the ID allocated for next new watching
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closed bool
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cancels []CancelFunc
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}
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// TODO: return error if ws is closed?
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func (ws *watcher) Watch(key []byte, prefix bool, startRev int64) (id int64, cancel CancelFunc) {
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ws.mu.Lock()
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defer ws.mu.Unlock()
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if ws.closed {
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return -1, nil
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}
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id = ws.nextID
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ws.nextID++
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_, c := ws.watchable.watch(key, prefix, startRev, id, ws.ch)
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// TODO: cancelFunc needs to be removed from the cancels when it is called.
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ws.cancels = append(ws.cancels, c)
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return id, c
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}
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func (ws *watcher) Chan() <-chan storagepb.Event {
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return ws.ch
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}
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func (ws *watcher) Close() {
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ws.mu.Lock()
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defer ws.mu.Unlock()
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for _, cancel := range ws.cancels {
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cancel()
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}
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ws.closed = true
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close(ws.ch)
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watcherGauge.Dec()
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}
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