mirror of
https://github.com/etcd-io/etcd.git
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108 lines
2.9 KiB
Go
108 lines
2.9 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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"errors"
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"sync"
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"github.com/coreos/etcd/storage/storagepb"
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)
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var (
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ErrWatcherNotExist = errors.New("storage: watcher does not exist")
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)
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type WatchStream interface {
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// Watch creates a watcher. The watcher watches the events happening or
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// happened on the given key or key prefix from the given startRev.
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//
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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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//
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// The returned `id` is the ID of this watcher. It appears as WatchID
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// in events that are sent to the created watcher through stream channel.
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//
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// TODO: remove the returned CancelFunc. Always use Cancel.
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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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// Cancel cancels a watcher by giving its ID. If watcher does not exist, an error will be
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// returned.
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Cancel(id int64) error
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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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// watchStream contains a collection of watchers that share
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// one streaming chan to send out watched events and other control events.
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type watchStream 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 is the ID pre-allocated for next new watcher in this stream
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nextID int64
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closed bool
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cancels map[int64]CancelFunc
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}
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// TODO: return error if ws is closed?
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func (ws *watchStream) 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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ws.cancels[id] = c
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return id, c
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}
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func (ws *watchStream) Chan() <-chan []storagepb.Event {
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return ws.ch
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}
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func (ws *watchStream) Cancel(id int64) error {
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cancel, ok := ws.cancels[id]
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if !ok {
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return ErrWatcherNotExist
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}
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cancel()
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delete(ws.cancels, id)
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return nil
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}
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func (ws *watchStream) 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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watchStreamGauge.Dec()
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}
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