mirror of
https://github.com/etcd-io/etcd.git
synced 2024-09-27 06:25:44 +00:00
89 lines
2.3 KiB
Go
89 lines
2.3 KiB
Go
// Copyright 2016 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 concurrency
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import (
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"sync"
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v3 "github.com/coreos/etcd/clientv3"
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"golang.org/x/net/context"
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)
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// Mutex implements the sync Locker interface with etcd
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type Mutex struct {
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client *v3.Client
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pfx string
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myKey string
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myRev int64
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}
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func NewMutex(client *v3.Client, pfx string) *Mutex {
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return &Mutex{client, pfx, "", -1}
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}
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// Lock locks the mutex with a cancellable context. If the context is cancelled
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// while trying to acquire the lock, the mutex tries to clean its stale lock entry.
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func (m *Mutex) Lock(ctx context.Context) error {
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s, err := NewSession(m.client)
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if err != nil {
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return err
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}
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// put self in lock waiters via myKey; oldest waiter holds lock
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m.myKey, m.myRev, err = NewUniqueKey(ctx, m.client, m.pfx, v3.WithLease(s.Lease()))
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// wait for deletion revisions prior to myKey
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err = waitDeletes(ctx, m.client, m.pfx, v3.WithPrefix(), v3.WithRev(m.myRev-1))
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// release lock key if cancelled
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select {
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case <-ctx.Done():
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m.Unlock()
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default:
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}
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return err
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}
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func (m *Mutex) Unlock() error {
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if _, err := m.client.Delete(m.client.Ctx(), m.myKey); err != nil {
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return err
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}
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m.myKey = "\x00"
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m.myRev = -1
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return nil
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}
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func (m *Mutex) IsOwner() v3.Cmp {
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return v3.Compare(v3.CreateRevision(m.myKey), "=", m.myRev)
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}
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func (m *Mutex) Key() string { return m.myKey }
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type lockerMutex struct{ *Mutex }
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func (lm *lockerMutex) Lock() {
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if err := lm.Mutex.Lock(lm.client.Ctx()); err != nil {
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panic(err)
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}
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}
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func (lm *lockerMutex) Unlock() {
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if err := lm.Mutex.Unlock(); err != nil {
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panic(err)
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}
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}
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// NewLocker creates a sync.Locker backed by an etcd mutex.
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func NewLocker(client *v3.Client, pfx string) sync.Locker {
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return &lockerMutex{NewMutex(client, pfx)}
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}
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