mirror of
https://github.com/etcd-io/etcd.git
synced 2024-09-27 06:25:44 +00:00
90 lines
2.4 KiB
Go
90 lines
2.4 KiB
Go
// Copyright 2016 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 recipe
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import (
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"context"
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v3 "go.etcd.io/etcd/clientv3"
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"go.etcd.io/etcd/clientv3/concurrency"
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"go.etcd.io/etcd/mvcc/mvccpb"
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)
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type RWMutex struct {
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s *concurrency.Session
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ctx context.Context
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pfx string
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myKey *EphemeralKV
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}
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func NewRWMutex(s *concurrency.Session, prefix string) *RWMutex {
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return &RWMutex{s, context.TODO(), prefix + "/", nil}
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}
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func (rwm *RWMutex) RLock() error {
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rk, err := newUniqueEphemeralKey(rwm.s, rwm.pfx+"read")
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if err != nil {
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return err
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}
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rwm.myKey = rk
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// wait until nodes with "write-" and a lower revision number than myKey are gone
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for {
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if done, werr := rwm.waitOnLastRev(rwm.pfx + "write"); done || werr != nil {
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return werr
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}
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}
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}
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func (rwm *RWMutex) Lock() error {
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rk, err := newUniqueEphemeralKey(rwm.s, rwm.pfx+"write")
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if err != nil {
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return err
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}
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rwm.myKey = rk
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// wait until all keys of lower revision than myKey are gone
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for {
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if done, werr := rwm.waitOnLastRev(rwm.pfx); done || werr != nil {
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return werr
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}
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// get the new lowest key until this is the only one left
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}
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}
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// waitOnLowest will wait on the last key with a revision < rwm.myKey.Revision with a
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// given prefix. If there are no keys left to wait on, return true.
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func (rwm *RWMutex) waitOnLastRev(pfx string) (bool, error) {
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client := rwm.s.Client()
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// get key that's blocking myKey
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opts := append(v3.WithLastRev(), v3.WithMaxModRev(rwm.myKey.Revision()-1))
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lastKey, err := client.Get(rwm.ctx, pfx, opts...)
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if err != nil {
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return false, err
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}
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if len(lastKey.Kvs) == 0 {
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return true, nil
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}
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// wait for release on blocking key
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_, err = WaitEvents(
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client,
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string(lastKey.Kvs[0].Key),
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rwm.myKey.Revision(),
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[]mvccpb.Event_EventType{mvccpb.DELETE})
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return false, err
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}
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func (rwm *RWMutex) RUnlock() error { return rwm.myKey.Delete() }
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func (rwm *RWMutex) Unlock() error { return rwm.myKey.Delete() }
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