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Scott Baker2c1c4822019-10-16 11:02:41 -07001/*
2 * Copyright 2018-present Open Networking Foundation
3
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7
8 * http://www.apache.org/licenses/LICENSE-2.0
9
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16package kvstore
17
18import (
19 "context"
20 "errors"
21 "fmt"
npujar5bf737f2020-01-16 19:35:25 +053022 "sync"
23
serkant.uluderyab38671c2019-11-01 09:35:38 -070024 "github.com/opencord/voltha-lib-go/v3/pkg/log"
Scott Baker2c1c4822019-10-16 11:02:41 -070025 v3Client "go.etcd.io/etcd/clientv3"
26 v3Concurrency "go.etcd.io/etcd/clientv3/concurrency"
27 v3rpcTypes "go.etcd.io/etcd/etcdserver/api/v3rpc/rpctypes"
Scott Baker2c1c4822019-10-16 11:02:41 -070028)
29
30// EtcdClient represents the Etcd KV store client
31type EtcdClient struct {
Matteo Scandoloed128822020-02-10 15:52:35 -080032 ectdAPI *v3Client.Client
33 keyReservations map[string]*v3Client.LeaseID
34 watchedChannels sync.Map
35 keyReservationsLock sync.RWMutex
36 lockToMutexMap map[string]*v3Concurrency.Mutex
37 lockToSessionMap map[string]*v3Concurrency.Session
38 lockToMutexLock sync.Mutex
Scott Baker2c1c4822019-10-16 11:02:41 -070039}
40
41// NewEtcdClient returns a new client for the Etcd KV store
42func NewEtcdClient(addr string, timeout int) (*EtcdClient, error) {
43 duration := GetDuration(timeout)
44
45 c, err := v3Client.New(v3Client.Config{
46 Endpoints: []string{addr},
47 DialTimeout: duration,
48 })
49 if err != nil {
khenaidoob332f9b2020-01-16 16:25:26 -050050 logger.Error(err)
Scott Baker2c1c4822019-10-16 11:02:41 -070051 return nil, err
52 }
53
54 reservations := make(map[string]*v3Client.LeaseID)
55 lockMutexMap := make(map[string]*v3Concurrency.Mutex)
56 lockSessionMap := make(map[string]*v3Concurrency.Session)
57
58 return &EtcdClient{ectdAPI: c, keyReservations: reservations, lockToMutexMap: lockMutexMap,
59 lockToSessionMap: lockSessionMap}, nil
60}
61
62// IsConnectionUp returns whether the connection to the Etcd KV store is up. If a timeout occurs then
63// it is assumed the connection is down or unreachable.
npujar5bf737f2020-01-16 19:35:25 +053064func (c *EtcdClient) IsConnectionUp(ctx context.Context) bool {
Scott Baker2c1c4822019-10-16 11:02:41 -070065 // Let's try to get a non existent key. If the connection is up then there will be no error returned.
npujar5bf737f2020-01-16 19:35:25 +053066 if _, err := c.Get(ctx, "non-existent-key"); err != nil {
Scott Baker2c1c4822019-10-16 11:02:41 -070067 return false
68 }
npujar5bf737f2020-01-16 19:35:25 +053069 //cancel()
Scott Baker2c1c4822019-10-16 11:02:41 -070070 return true
71}
72
73// List returns an array of key-value pairs with key as a prefix. Timeout defines how long the function will
74// wait for a response
npujar5bf737f2020-01-16 19:35:25 +053075func (c *EtcdClient) List(ctx context.Context, key string) (map[string]*KVPair, error) {
Scott Baker2c1c4822019-10-16 11:02:41 -070076 resp, err := c.ectdAPI.Get(ctx, key, v3Client.WithPrefix())
Scott Baker2c1c4822019-10-16 11:02:41 -070077 if err != nil {
khenaidoob332f9b2020-01-16 16:25:26 -050078 logger.Error(err)
Scott Baker2c1c4822019-10-16 11:02:41 -070079 return nil, err
80 }
81 m := make(map[string]*KVPair)
82 for _, ev := range resp.Kvs {
83 m[string(ev.Key)] = NewKVPair(string(ev.Key), ev.Value, "", ev.Lease, ev.Version)
84 }
85 return m, nil
86}
87
88// Get returns a key-value pair for a given key. Timeout defines how long the function will
89// wait for a response
npujar5bf737f2020-01-16 19:35:25 +053090func (c *EtcdClient) Get(ctx context.Context, key string) (*KVPair, error) {
Scott Baker2c1c4822019-10-16 11:02:41 -070091
92 resp, err := c.ectdAPI.Get(ctx, key)
npujar5bf737f2020-01-16 19:35:25 +053093
Scott Baker2c1c4822019-10-16 11:02:41 -070094 if err != nil {
khenaidoob332f9b2020-01-16 16:25:26 -050095 logger.Error(err)
Scott Baker2c1c4822019-10-16 11:02:41 -070096 return nil, err
97 }
98 for _, ev := range resp.Kvs {
99 // Only one value is returned
100 return NewKVPair(string(ev.Key), ev.Value, "", ev.Lease, ev.Version), nil
101 }
102 return nil, nil
103}
104
105// Put writes a key-value pair to the KV store. Value can only be a string or []byte since the etcd API
106// accepts only a string as a value for a put operation. Timeout defines how long the function will
107// wait for a response
npujar5bf737f2020-01-16 19:35:25 +0530108func (c *EtcdClient) Put(ctx context.Context, key string, value interface{}) error {
Scott Baker2c1c4822019-10-16 11:02:41 -0700109
110 // Validate that we can convert value to a string as etcd API expects a string
111 var val string
112 var er error
113 if val, er = ToString(value); er != nil {
114 return fmt.Errorf("unexpected-type-%T", value)
115 }
116
Scott Baker2c1c4822019-10-16 11:02:41 -0700117 var err error
118 // Check if there is already a lease for this key - if there is then use it, otherwise a PUT will make
119 // that KV key permanent instead of automatically removing it after a lease expiration
Matteo Scandoloed128822020-02-10 15:52:35 -0800120 c.keyReservationsLock.RLock()
121 leaseID, ok := c.keyReservations[key]
122 c.keyReservationsLock.RUnlock()
123 if ok {
Scott Baker2c1c4822019-10-16 11:02:41 -0700124 _, err = c.ectdAPI.Put(ctx, key, val, v3Client.WithLease(*leaseID))
125 } else {
126 _, err = c.ectdAPI.Put(ctx, key, val)
127 }
npujar5bf737f2020-01-16 19:35:25 +0530128
Scott Baker2c1c4822019-10-16 11:02:41 -0700129 if err != nil {
130 switch err {
131 case context.Canceled:
khenaidoob332f9b2020-01-16 16:25:26 -0500132 logger.Warnw("context-cancelled", log.Fields{"error": err})
Scott Baker2c1c4822019-10-16 11:02:41 -0700133 case context.DeadlineExceeded:
khenaidoob332f9b2020-01-16 16:25:26 -0500134 logger.Warnw("context-deadline-exceeded", log.Fields{"error": err})
Scott Baker2c1c4822019-10-16 11:02:41 -0700135 case v3rpcTypes.ErrEmptyKey:
khenaidoob332f9b2020-01-16 16:25:26 -0500136 logger.Warnw("etcd-client-error", log.Fields{"error": err})
Scott Baker2c1c4822019-10-16 11:02:41 -0700137 default:
khenaidoob332f9b2020-01-16 16:25:26 -0500138 logger.Warnw("bad-endpoints", log.Fields{"error": err})
Scott Baker2c1c4822019-10-16 11:02:41 -0700139 }
140 return err
141 }
142 return nil
143}
144
145// Delete removes a key from the KV store. Timeout defines how long the function will
146// wait for a response
npujar5bf737f2020-01-16 19:35:25 +0530147func (c *EtcdClient) Delete(ctx context.Context, key string) error {
Scott Baker2c1c4822019-10-16 11:02:41 -0700148
Scott Baker2c1c4822019-10-16 11:02:41 -0700149 // delete the key
150 if _, err := c.ectdAPI.Delete(ctx, key); err != nil {
khenaidoob332f9b2020-01-16 16:25:26 -0500151 logger.Errorw("failed-to-delete-key", log.Fields{"key": key, "error": err})
Scott Baker2c1c4822019-10-16 11:02:41 -0700152 return err
153 }
khenaidoob332f9b2020-01-16 16:25:26 -0500154 logger.Debugw("key(s)-deleted", log.Fields{"key": key})
Scott Baker2c1c4822019-10-16 11:02:41 -0700155 return nil
156}
157
158// Reserve is invoked to acquire a key and set it to a given value. Value can only be a string or []byte since
159// the etcd API accepts only a string. Timeout defines how long the function will wait for a response. TTL
160// defines how long that reservation is valid. When TTL expires the key is unreserved by the KV store itself.
161// If the key is acquired then the value returned will be the value passed in. If the key is already acquired
162// then the value assigned to that key will be returned.
npujar5bf737f2020-01-16 19:35:25 +0530163func (c *EtcdClient) Reserve(ctx context.Context, key string, value interface{}, ttl int64) (interface{}, error) {
Scott Baker2c1c4822019-10-16 11:02:41 -0700164 // Validate that we can convert value to a string as etcd API expects a string
165 var val string
166 var er error
167 if val, er = ToString(value); er != nil {
168 return nil, fmt.Errorf("unexpected-type%T", value)
169 }
170
Thomas Lee S86fc9362019-10-31 11:35:19 +0530171 resp, err := c.ectdAPI.Grant(ctx, ttl)
Scott Baker2c1c4822019-10-16 11:02:41 -0700172 if err != nil {
khenaidoob332f9b2020-01-16 16:25:26 -0500173 logger.Error(err)
Scott Baker2c1c4822019-10-16 11:02:41 -0700174 return nil, err
175 }
176 // Register the lease id
Matteo Scandoloed128822020-02-10 15:52:35 -0800177 c.keyReservationsLock.Lock()
Scott Baker2c1c4822019-10-16 11:02:41 -0700178 c.keyReservations[key] = &resp.ID
Matteo Scandoloed128822020-02-10 15:52:35 -0800179 c.keyReservationsLock.Unlock()
Scott Baker2c1c4822019-10-16 11:02:41 -0700180
181 // Revoke lease if reservation is not successful
182 reservationSuccessful := false
183 defer func() {
184 if !reservationSuccessful {
npujar5bf737f2020-01-16 19:35:25 +0530185 if err = c.ReleaseReservation(context.Background(), key); err != nil {
khenaidoob332f9b2020-01-16 16:25:26 -0500186 logger.Error("cannot-release-lease")
Scott Baker2c1c4822019-10-16 11:02:41 -0700187 }
188 }
189 }()
190
191 // Try to grap the Key with the above lease
192 c.ectdAPI.Txn(context.Background())
193 txn := c.ectdAPI.Txn(context.Background())
194 txn = txn.If(v3Client.Compare(v3Client.Version(key), "=", 0))
195 txn = txn.Then(v3Client.OpPut(key, val, v3Client.WithLease(resp.ID)))
196 txn = txn.Else(v3Client.OpGet(key))
197 result, er := txn.Commit()
198 if er != nil {
199 return nil, er
200 }
201
202 if !result.Succeeded {
203 // Verify whether we are already the owner of that Key
204 if len(result.Responses) > 0 &&
205 len(result.Responses[0].GetResponseRange().Kvs) > 0 {
206 kv := result.Responses[0].GetResponseRange().Kvs[0]
207 if string(kv.Value) == val {
208 reservationSuccessful = true
209 return value, nil
210 }
211 return kv.Value, nil
212 }
213 } else {
214 // Read the Key to ensure this is our Key
npujar5bf737f2020-01-16 19:35:25 +0530215 m, err := c.Get(ctx, key)
Scott Baker2c1c4822019-10-16 11:02:41 -0700216 if err != nil {
217 return nil, err
218 }
219 if m != nil {
220 if m.Key == key && isEqual(m.Value, value) {
221 // My reservation is successful - register it. For now, support is only for 1 reservation per key
222 // per session.
223 reservationSuccessful = true
224 return value, nil
225 }
226 // My reservation has failed. Return the owner of that key
227 return m.Value, nil
228 }
229 }
230 return nil, nil
231}
232
233// ReleaseAllReservations releases all key reservations previously made (using Reserve API)
npujar5bf737f2020-01-16 19:35:25 +0530234func (c *EtcdClient) ReleaseAllReservations(ctx context.Context) error {
Matteo Scandoloed128822020-02-10 15:52:35 -0800235 c.keyReservationsLock.Lock()
236 defer c.keyReservationsLock.Unlock()
Thomas Lee S86fc9362019-10-31 11:35:19 +0530237
Scott Baker2c1c4822019-10-16 11:02:41 -0700238 for key, leaseID := range c.keyReservations {
Thomas Lee S86fc9362019-10-31 11:35:19 +0530239 _, err := c.ectdAPI.Revoke(ctx, *leaseID)
Scott Baker2c1c4822019-10-16 11:02:41 -0700240 if err != nil {
khenaidoob332f9b2020-01-16 16:25:26 -0500241 logger.Errorw("cannot-release-reservation", log.Fields{"key": key, "error": err})
Scott Baker2c1c4822019-10-16 11:02:41 -0700242 return err
243 }
244 delete(c.keyReservations, key)
245 }
246 return nil
247}
248
249// ReleaseReservation releases reservation for a specific key.
npujar5bf737f2020-01-16 19:35:25 +0530250func (c *EtcdClient) ReleaseReservation(ctx context.Context, key string) error {
Scott Baker2c1c4822019-10-16 11:02:41 -0700251 // Get the leaseid using the key
khenaidoob332f9b2020-01-16 16:25:26 -0500252 logger.Debugw("Release-reservation", log.Fields{"key": key})
Scott Baker2c1c4822019-10-16 11:02:41 -0700253 var ok bool
254 var leaseID *v3Client.LeaseID
Matteo Scandoloed128822020-02-10 15:52:35 -0800255 c.keyReservationsLock.Lock()
256 defer c.keyReservationsLock.Unlock()
Scott Baker2c1c4822019-10-16 11:02:41 -0700257 if leaseID, ok = c.keyReservations[key]; !ok {
258 return nil
259 }
Thomas Lee S86fc9362019-10-31 11:35:19 +0530260
Scott Baker2c1c4822019-10-16 11:02:41 -0700261 if leaseID != nil {
Thomas Lee S86fc9362019-10-31 11:35:19 +0530262 _, err := c.ectdAPI.Revoke(ctx, *leaseID)
Scott Baker2c1c4822019-10-16 11:02:41 -0700263 if err != nil {
khenaidoob332f9b2020-01-16 16:25:26 -0500264 logger.Error(err)
Scott Baker2c1c4822019-10-16 11:02:41 -0700265 return err
266 }
267 delete(c.keyReservations, key)
268 }
269 return nil
270}
271
272// RenewReservation renews a reservation. A reservation will go stale after the specified TTL (Time To Live)
273// period specified when reserving the key
npujar5bf737f2020-01-16 19:35:25 +0530274func (c *EtcdClient) RenewReservation(ctx context.Context, key string) error {
Scott Baker2c1c4822019-10-16 11:02:41 -0700275 // Get the leaseid using the key
276 var ok bool
277 var leaseID *v3Client.LeaseID
Matteo Scandoloed128822020-02-10 15:52:35 -0800278 c.keyReservationsLock.RLock()
279 leaseID, ok = c.keyReservations[key]
280 c.keyReservationsLock.RUnlock()
281
282 if !ok {
Scott Baker2c1c4822019-10-16 11:02:41 -0700283 return errors.New("key-not-reserved")
284 }
285
286 if leaseID != nil {
Thomas Lee S86fc9362019-10-31 11:35:19 +0530287 _, err := c.ectdAPI.KeepAliveOnce(ctx, *leaseID)
Scott Baker2c1c4822019-10-16 11:02:41 -0700288 if err != nil {
khenaidoob332f9b2020-01-16 16:25:26 -0500289 logger.Errorw("lease-may-have-expired", log.Fields{"error": err})
Scott Baker2c1c4822019-10-16 11:02:41 -0700290 return err
291 }
292 } else {
293 return errors.New("lease-expired")
294 }
295 return nil
296}
297
298// Watch provides the watch capability on a given key. It returns a channel onto which the callee needs to
299// listen to receive Events.
divyadesai8bf96862020-02-07 12:24:26 +0000300func (c *EtcdClient) Watch(ctx context.Context, key string, withPrefix bool) chan *Event {
Scott Baker2c1c4822019-10-16 11:02:41 -0700301 w := v3Client.NewWatcher(c.ectdAPI)
npujar5bf737f2020-01-16 19:35:25 +0530302 ctx, cancel := context.WithCancel(ctx)
divyadesai8bf96862020-02-07 12:24:26 +0000303 var channel v3Client.WatchChan
304 if withPrefix {
305 channel = w.Watch(ctx, key, v3Client.WithPrefix())
306 } else {
307 channel = w.Watch(ctx, key)
308 }
Scott Baker2c1c4822019-10-16 11:02:41 -0700309
310 // Create a new channel
311 ch := make(chan *Event, maxClientChannelBufferSize)
312
313 // Keep track of the created channels so they can be closed when required
314 channelMap := make(map[chan *Event]v3Client.Watcher)
315 channelMap[ch] = w
316
317 channelMaps := c.addChannelMap(key, channelMap)
318
319 // Changing the log field (from channelMaps) as the underlying logger cannot format the map of channels into a
320 // json format.
khenaidoob332f9b2020-01-16 16:25:26 -0500321 logger.Debugw("watched-channels", log.Fields{"len": len(channelMaps)})
Scott Baker2c1c4822019-10-16 11:02:41 -0700322 // Launch a go routine to listen for updates
323 go c.listenForKeyChange(channel, ch, cancel)
324
325 return ch
326
327}
328
329func (c *EtcdClient) addChannelMap(key string, channelMap map[chan *Event]v3Client.Watcher) []map[chan *Event]v3Client.Watcher {
330 var channels interface{}
331 var exists bool
332
333 if channels, exists = c.watchedChannels.Load(key); exists {
334 channels = append(channels.([]map[chan *Event]v3Client.Watcher), channelMap)
335 } else {
336 channels = []map[chan *Event]v3Client.Watcher{channelMap}
337 }
338 c.watchedChannels.Store(key, channels)
339
340 return channels.([]map[chan *Event]v3Client.Watcher)
341}
342
343func (c *EtcdClient) removeChannelMap(key string, pos int) []map[chan *Event]v3Client.Watcher {
344 var channels interface{}
345 var exists bool
346
347 if channels, exists = c.watchedChannels.Load(key); exists {
348 channels = append(channels.([]map[chan *Event]v3Client.Watcher)[:pos], channels.([]map[chan *Event]v3Client.Watcher)[pos+1:]...)
349 c.watchedChannels.Store(key, channels)
350 }
351
352 return channels.([]map[chan *Event]v3Client.Watcher)
353}
354
355func (c *EtcdClient) getChannelMaps(key string) ([]map[chan *Event]v3Client.Watcher, bool) {
356 var channels interface{}
357 var exists bool
358
359 channels, exists = c.watchedChannels.Load(key)
360
361 if channels == nil {
362 return nil, exists
363 }
364
365 return channels.([]map[chan *Event]v3Client.Watcher), exists
366}
367
368// CloseWatch closes a specific watch. Both the key and the channel are required when closing a watch as there
369// may be multiple listeners on the same key. The previously created channel serves as a key
370func (c *EtcdClient) CloseWatch(key string, ch chan *Event) {
371 // Get the array of channels mapping
372 var watchedChannels []map[chan *Event]v3Client.Watcher
373 var ok bool
Scott Baker2c1c4822019-10-16 11:02:41 -0700374
375 if watchedChannels, ok = c.getChannelMaps(key); !ok {
khenaidoob332f9b2020-01-16 16:25:26 -0500376 logger.Warnw("key-has-no-watched-channels", log.Fields{"key": key})
Scott Baker2c1c4822019-10-16 11:02:41 -0700377 return
378 }
379 // Look for the channels
380 var pos = -1
381 for i, chMap := range watchedChannels {
382 if t, ok := chMap[ch]; ok {
khenaidoob332f9b2020-01-16 16:25:26 -0500383 logger.Debug("channel-found")
Scott Baker2c1c4822019-10-16 11:02:41 -0700384 // Close the etcd watcher before the client channel. This should close the etcd channel as well
385 if err := t.Close(); err != nil {
khenaidoob332f9b2020-01-16 16:25:26 -0500386 logger.Errorw("watcher-cannot-be-closed", log.Fields{"key": key, "error": err})
Scott Baker2c1c4822019-10-16 11:02:41 -0700387 }
388 pos = i
389 break
390 }
391 }
392
393 channelMaps, _ := c.getChannelMaps(key)
394 // Remove that entry if present
395 if pos >= 0 {
396 channelMaps = c.removeChannelMap(key, pos)
397 }
khenaidoob332f9b2020-01-16 16:25:26 -0500398 logger.Infow("watcher-channel-exiting", log.Fields{"key": key, "channel": channelMaps})
Scott Baker2c1c4822019-10-16 11:02:41 -0700399}
400
401func (c *EtcdClient) listenForKeyChange(channel v3Client.WatchChan, ch chan<- *Event, cancel context.CancelFunc) {
khenaidoob332f9b2020-01-16 16:25:26 -0500402 logger.Debug("start-listening-on-channel ...")
Scott Baker2c1c4822019-10-16 11:02:41 -0700403 defer cancel()
404 defer close(ch)
405 for resp := range channel {
406 for _, ev := range resp.Events {
407 ch <- NewEvent(getEventType(ev), ev.Kv.Key, ev.Kv.Value, ev.Kv.Version)
408 }
409 }
khenaidoob332f9b2020-01-16 16:25:26 -0500410 logger.Debug("stop-listening-on-channel ...")
Scott Baker2c1c4822019-10-16 11:02:41 -0700411}
412
413func getEventType(event *v3Client.Event) int {
414 switch event.Type {
415 case v3Client.EventTypePut:
416 return PUT
417 case v3Client.EventTypeDelete:
418 return DELETE
419 }
420 return UNKNOWN
421}
422
423// Close closes the KV store client
424func (c *EtcdClient) Close() {
Scott Baker2c1c4822019-10-16 11:02:41 -0700425 if err := c.ectdAPI.Close(); err != nil {
khenaidoob332f9b2020-01-16 16:25:26 -0500426 logger.Errorw("error-closing-client", log.Fields{"error": err})
Scott Baker2c1c4822019-10-16 11:02:41 -0700427 }
428}
429
430func (c *EtcdClient) addLockName(lockName string, lock *v3Concurrency.Mutex, session *v3Concurrency.Session) {
431 c.lockToMutexLock.Lock()
432 defer c.lockToMutexLock.Unlock()
433 c.lockToMutexMap[lockName] = lock
434 c.lockToSessionMap[lockName] = session
435}
436
437func (c *EtcdClient) deleteLockName(lockName string) {
438 c.lockToMutexLock.Lock()
439 defer c.lockToMutexLock.Unlock()
440 delete(c.lockToMutexMap, lockName)
441 delete(c.lockToSessionMap, lockName)
442}
443
444func (c *EtcdClient) getLock(lockName string) (*v3Concurrency.Mutex, *v3Concurrency.Session) {
445 c.lockToMutexLock.Lock()
446 defer c.lockToMutexLock.Unlock()
447 var lock *v3Concurrency.Mutex
448 var session *v3Concurrency.Session
449 if l, exist := c.lockToMutexMap[lockName]; exist {
450 lock = l
451 }
452 if s, exist := c.lockToSessionMap[lockName]; exist {
453 session = s
454 }
455 return lock, session
456}
457
npujar5bf737f2020-01-16 19:35:25 +0530458func (c *EtcdClient) AcquireLock(ctx context.Context, lockName string, timeout int) error {
Scott Baker2c1c4822019-10-16 11:02:41 -0700459 session, _ := v3Concurrency.NewSession(c.ectdAPI, v3Concurrency.WithContext(ctx))
460 mu := v3Concurrency.NewMutex(session, "/devicelock_"+lockName)
461 if err := mu.Lock(context.Background()); err != nil {
npujar5bf737f2020-01-16 19:35:25 +0530462 //cancel()
Scott Baker2c1c4822019-10-16 11:02:41 -0700463 return err
464 }
465 c.addLockName(lockName, mu, session)
466 return nil
467}
468
469func (c *EtcdClient) ReleaseLock(lockName string) error {
470 lock, session := c.getLock(lockName)
471 var err error
472 if lock != nil {
473 if e := lock.Unlock(context.Background()); e != nil {
474 err = e
475 }
476 }
477 if session != nil {
478 if e := session.Close(); e != nil {
479 err = e
480 }
481 }
482 c.deleteLockName(lockName)
483
484 return err
485}