db/kvstore/etcdclient.go - voltha-go - Gitiles

 /*
  * Copyright 2018-present Open Networking Foundation

  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
  * You may obtain a copy of the License at

  * http://www.apache.org/licenses/LICENSE-2.0

  * Unless required by applicable law or agreed to in writing, software
  * distributed under the License is distributed on an "AS IS" BASIS,
  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
 package kvstore

 import (
 	"context"
 	"errors"
 	"fmt"
 	"github.com/opencord/voltha-go/common/log"
 	v3Client "go.etcd.io/etcd/clientv3"
 	v3Concurrency "go.etcd.io/etcd/clientv3/concurrency"
 	v3rpcTypes "go.etcd.io/etcd/etcdserver/api/v3rpc/rpctypes"
 	"sync"
 )

 // EtcdClient represents the Etcd KV store client
 type EtcdClient struct {
 	ectdAPI         *v3Client.Client
 	leaderRev       v3Client.Client
 	keyReservations map[string]*v3Client.LeaseID
 	watchedChannels map[string][]map[chan *Event]v3Client.Watcher
 	writeLock       sync.Mutex
 }

 // NewEtcdClient returns a new client for the Etcd KV store
 func NewEtcdClient(addr string, timeout int) (*EtcdClient, error) {
 	duration := GetDuration(timeout)

 	c, err := v3Client.New(v3Client.Config{
 		Endpoints:   []string{addr},
 		DialTimeout: duration,
 	})
 	if err != nil {
 		log.Error(err)
 		return nil, err
 	}
 	wc := make(map[string][]map[chan *Event]v3Client.Watcher)
 	reservations := make(map[string]*v3Client.LeaseID)

 	return &EtcdClient{ectdAPI: c, watchedChannels: wc, keyReservations: reservations}, nil
 }

 // List returns an array of key-value pairs with key as a prefix.  Timeout defines how long the function will
 // wait for a response
 func (c *EtcdClient) List(key string, timeout int, lock ...bool) (map[string]*KVPair, error) {
 	duration := GetDuration(timeout)

 	ctx, cancel := context.WithTimeout(context.Background(), duration)

 	// DO NOT lock by default; otherwise lock per instructed value
 	if len(lock) > 0 && lock[0] {
 		session, _ := v3Concurrency.NewSession(c.ectdAPI, v3Concurrency.WithContext(ctx))
 		mu := v3Concurrency.NewMutex(session, "/lock" + key)
 		mu.Lock(context.Background())
 		defer mu.Unlock(context.Background())
 		defer session.Close()
 	}

 	resp, err := c.ectdAPI.Get(ctx, key, v3Client.WithPrefix())
 	cancel()
 	if err != nil {
 		log.Error(err)
 		return nil, err
 	}
 	m := make(map[string]*KVPair)
 	for _, ev := range resp.Kvs {
 		m[string(ev.Key)] = NewKVPair(string(ev.Key), ev.Value, "", ev.Lease)
 	}
 	return m, nil
 }

 // Get returns a key-value pair for a given key. Timeout defines how long the function will
 // wait for a response
 func (c *EtcdClient) Get(key string, timeout int, lock ...bool) (*KVPair, error) {
 	duration := GetDuration(timeout)

 	ctx, cancel := context.WithTimeout(context.Background(), duration)

 	// Lock by default; otherwise lock per instructed value
 	if len(lock) == 0 || lock[0] {
 		session, _ := v3Concurrency.NewSession(c.ectdAPI, v3Concurrency.WithContext(ctx))
 		mu := v3Concurrency.NewMutex(session, "/lock" + key)
 		mu.Lock(context.Background())
 		defer mu.Unlock(context.Background())
 		defer session.Close()
 	}

 	resp, err := c.ectdAPI.Get(ctx, key)
 	cancel()
 	if err != nil {
 		log.Error(err)
 		return nil, err
 	}
 	for _, ev := range resp.Kvs {
 		// Only one value is returned
 		return NewKVPair(string(ev.Key), ev.Value, "", ev.Lease), nil
 	}
 	return nil, nil
 }

 // Put writes a key-value pair to the KV store.  Value can only be a string or []byte since the etcd API
 // accepts only a string as a value for a put operation. Timeout defines how long the function will
 // wait for a response
 func (c *EtcdClient) Put(key string, value interface{}, timeout int, lock ...bool) error {

 	// Validate that we can convert value to a string as etcd API expects a string
 	var val string
 	var er error
 	if val, er = ToString(value); er != nil {
 		return fmt.Errorf("unexpected-type-%T", value)
 	}

 	duration := GetDuration(timeout)

 	ctx, cancel := context.WithTimeout(context.Background(), duration)

 	// Lock by default; otherwise lock per instructed value
 	if len(lock) == 0 || lock[0] {
 		session, _ := v3Concurrency.NewSession(c.ectdAPI, v3Concurrency.WithContext(ctx))
 		mu := v3Concurrency.NewMutex(session, "/lock" + key)
 		mu.Lock(context.Background())
 		defer mu.Unlock(context.Background())
 		defer session.Close()
 	}

 	c.writeLock.Lock()
 	defer c.writeLock.Unlock()
 	_, err := c.ectdAPI.Put(ctx, key, val)
 	cancel()
 	if err != nil {
 		switch err {
 		case context.Canceled:
 			log.Warnw("context-cancelled", log.Fields{"error": err})
 		case context.DeadlineExceeded:
 			log.Warnw("context-deadline-exceeded", log.Fields{"error": err})
 		case v3rpcTypes.ErrEmptyKey:
 			log.Warnw("etcd-client-error", log.Fields{"error": err})
 		default:
 			log.Warnw("bad-endpoints", log.Fields{"error": err})
 		}
 		return err
 	}
 	return nil
 }

 // Delete removes a key from the KV store. Timeout defines how long the function will
 // wait for a response
 func (c *EtcdClient) Delete(key string, timeout int, lock ...bool) error {

 	duration := GetDuration(timeout)

 	ctx, cancel := context.WithTimeout(context.Background(), duration)

 	// Lock by default; otherwise lock per instructed value
 	if len(lock) == 0 || lock[0] {
 		session, _ := v3Concurrency.NewSession(c.ectdAPI, v3Concurrency.WithContext(ctx))
 		mu := v3Concurrency.NewMutex(session, "/lock" + key)
 		mu.Lock(context.Background())
 		defer mu.Unlock(context.Background())
 		defer session.Close()
 	}

 	defer cancel()

 	c.writeLock.Lock()
 	defer c.writeLock.Unlock()

 	// count keys about to be deleted
 	gresp, err := c.ectdAPI.Get(ctx, key, v3Client.WithPrefix())
 	if err != nil {
 		log.Error(err)
 		return err
 	}

 	// delete the keys
 	dresp, err := c.ectdAPI.Delete(ctx, key, v3Client.WithPrefix())
 	if err != nil {
 		log.Error(err)
 		return err
 	}

 	if dresp == nil || gresp == nil {
 		log.Debug("nothing-to-delete")
 		return nil
 	}

 	log.Debugw("delete-keys", log.Fields{"all-keys-deleted": int64(len(gresp.Kvs)) == dresp.Deleted})
 	if int64(len(gresp.Kvs)) == dresp.Deleted {
 		log.Debug("All-keys-deleted")
 	} else {
 		log.Error("not-all-keys-deleted")
 		err := errors.New("not-all-keys-deleted")
 		return err
 	}
 	return nil
 }

 // Reserve is invoked to acquire a key and set it to a given value. Value can only be a string or []byte since
 // the etcd API accepts only a string.  Timeout defines how long the function will wait for a response.  TTL
 // defines how long that reservation is valid.  When TTL expires the key is unreserved by the KV store itself.
 // If the key is acquired then the value returned will be the value passed in.  If the key is already acquired
 // then the value assigned to that key will be returned.
 func (c *EtcdClient) Reserve(key string, value interface{}, ttl int64) (interface{}, error) {
 	// Validate that we can convert value to a string as etcd API expects a string
 	var val string
 	var er error
 	if val, er = ToString(value); er != nil {
 		return nil, fmt.Errorf("unexpected-type%T", value)
 	}

 	// Create a lease
 	resp, err := c.ectdAPI.Grant(context.Background(), ttl)
 	if err != nil {
 		log.Error(err)
 		return nil, err
 	}
 	// Register the lease id
 	c.writeLock.Lock()
 	c.keyReservations[key] = &resp.ID
 	c.writeLock.Unlock()

 	// Revoke lease if reservation is not successful
 	reservationSuccessful := false
 	defer func() {
 		if !reservationSuccessful {
 			if err = c.ReleaseReservation(key); err != nil {
 				log.Errorf("cannot-release-lease")
 			}
 		}
 	}()

 	// Try to grap the Key with the above lease
 	c.ectdAPI.Txn(context.Background())
 	txn := c.ectdAPI.Txn(context.Background())
 	txn = txn.If(v3Client.Compare(v3Client.Version(key), "=", 0))
 	txn = txn.Then(v3Client.OpPut(key, val, v3Client.WithLease(resp.ID)))
 	txn = txn.Else(v3Client.OpGet(key))
 	result, er := txn.Commit()
 	if er != nil {
 		return nil, er
 	}

 	if !result.Succeeded {
 		// Verify whether we are already the owner of that Key
 		if len(result.Responses) > 0 &&
 			len(result.Responses[0].GetResponseRange().Kvs) > 0 {
 			kv := result.Responses[0].GetResponseRange().Kvs[0]
 			if string(kv.Value) == val {
 				reservationSuccessful = true
 				return value, nil
 			}
 			return kv.Value, nil
 		}
 	} else {
 		// Read the Key to ensure this is our Key
 		m, err := c.Get(key, defaultKVGetTimeout, false)
 		if err != nil {
 			return nil, err
 		}
 		if m != nil {
 			if m.Key == key && isEqual(m.Value, value) {
 				// My reservation is successful - register it.  For now, support is only for 1 reservation per key
 				// per session.
 				reservationSuccessful = true
 				return value, nil
 			}
 			// My reservation has failed.  Return the owner of that key
 			return m.Value, nil
 		}
 	}
 	return nil, nil
 }

 // ReleaseAllReservations releases all key reservations previously made (using Reserve API)
 func (c *EtcdClient) ReleaseAllReservations() error {
 	c.writeLock.Lock()
 	defer c.writeLock.Unlock()
 	for key, leaseID := range c.keyReservations {
 		_, err := c.ectdAPI.Revoke(context.Background(), *leaseID)
 		if err != nil {
 			log.Errorw("cannot-release-reservation", log.Fields{"key": key, "error": err})
 			return err
 		}
 		delete(c.keyReservations, key)
 	}
 	return nil
 }

 // ReleaseReservation releases reservation for a specific key.
 func (c *EtcdClient) ReleaseReservation(key string) error {
 	// Get the leaseid using the key
 	var ok bool
 	var leaseID *v3Client.LeaseID
 	c.writeLock.Lock()
 	defer c.writeLock.Unlock()
 	if leaseID, ok = c.keyReservations[key]; !ok {
 		return errors.New("key-not-reserved")
 	}
 	if leaseID != nil {
 		_, err := c.ectdAPI.Revoke(context.Background(), *leaseID)
 		if err != nil {
 			log.Error(err)
 			return err
 		}
 		delete(c.keyReservations, key)
 	}
 	return nil
 }

 // RenewReservation renews a reservation.  A reservation will go stale after the specified TTL (Time To Live)
 // period specified when reserving the key
 func (c *EtcdClient) RenewReservation(key string) error {
 	// Get the leaseid using the key
 	var ok bool
 	var leaseID *v3Client.LeaseID
 	c.writeLock.Lock()
 	defer c.writeLock.Unlock()
 	if leaseID, ok = c.keyReservations[key]; !ok {
 		return errors.New("key-not-reserved")
 	}

 	if leaseID != nil {
 		_, err := c.ectdAPI.KeepAliveOnce(context.Background(), *leaseID)
 		if err != nil {
 			log.Errorw("lease-may-have-expired", log.Fields{"error": err})
 			return err
 		}
 	} else {
 		return errors.New("lease-expired")
 	}
 	return nil
 }

 // Watch provides the watch capability on a given key.  It returns a channel onto which the callee needs to
 // listen to receive Events.
 func (c *EtcdClient) Watch(key string) chan *Event {
 	w := v3Client.NewWatcher(c.ectdAPI)
 	channel := w.Watch(context.Background(), key, v3Client.WithPrefix())

 	// Create a new channel
 	ch := make(chan *Event, maxClientChannelBufferSize)

 	// Keep track of the created channels so they can be closed when required
 	channelMap := make(map[chan *Event]v3Client.Watcher)
 	channelMap[ch] = w
 	//c.writeLock.Lock()
 	//defer c.writeLock.Unlock()
 	c.watchedChannels[key] = append(c.watchedChannels[key], channelMap)

 	log.Debugw("watched-channels", log.Fields{"channels": c.watchedChannels[key]})
 	// Launch a go routine to listen for updates
 	go c.listenForKeyChange(channel, ch)

 	return ch

 }

 // CloseWatch closes a specific watch. Both the key and the channel are required when closing a watch as there
 // may be multiple listeners on the same key.  The previously created channel serves as a key
 func (c *EtcdClient) CloseWatch(key string, ch chan *Event) {
 	// Get the array of channels mapping
 	var watchedChannels []map[chan *Event]v3Client.Watcher
 	var ok bool
 	c.writeLock.Lock()
 	defer c.writeLock.Unlock()

 	if watchedChannels, ok = c.watchedChannels[key]; !ok {
 		log.Warnw("key-has-no-watched-channels", log.Fields{"key": key})
 		return
 	}
 	// Look for the channels
 	var pos = -1
 	for i, chMap := range watchedChannels {
 		if t, ok := chMap[ch]; ok {
 			log.Debug("channel-found")
 			// Close the etcd watcher before the client channel.  This should close the etcd channel as well
 			if err := t.Close(); err != nil {
 				log.Errorw("watcher-cannot-be-closed", log.Fields{"key": key, "error": err})
 			}
 			close(ch)
 			pos = i
 			break
 		}
 	}
 	// Remove that entry if present
 	if pos >= 0 {
 		c.watchedChannels[key] = append(c.watchedChannels[key][:pos], c.watchedChannels[key][pos+1:]...)
 	}
 	log.Infow("watcher-channel-exiting", log.Fields{"key": key, "channel": c.watchedChannels[key]})
 }

 func (c *EtcdClient) listenForKeyChange(channel v3Client.WatchChan, ch chan<- *Event) {
 	log.Infow("start-listening-on-channel", log.Fields{"channel": ch})
 	for resp := range channel {
 		for _, ev := range resp.Events {
 			//log.Debugf("%s %q : %q\n", ev.Type, ev.Kv.Key, ev.Kv.Value)
 			ch <- NewEvent(getEventType(ev), ev.Kv.Key, ev.Kv.Value)
 		}
 	}
 	log.Info("stop-listening-on-channel")
 }

 func getEventType(event *v3Client.Event) int {
 	switch event.Type {
 	case v3Client.EventTypePut:
 		return PUT
 	case v3Client.EventTypeDelete:
 		return DELETE
 	}
 	return UNKNOWN
 }

 // Close closes the KV store client
 func (c *EtcdClient) Close() {
 	c.writeLock.Lock()
 	defer c.writeLock.Unlock()
 	if err := c.ectdAPI.Close(); err != nil {
 		log.Errorw("error-closing-client", log.Fields{"error": err})
 	}
 }
	/*
	* Copyright 2018-present Open Networking Foundation

	* Licensed under the Apache License, Version 2.0 (the "License");
	* you may not use this file except in compliance with the License.
	* You may obtain a copy of the License at

	* http://www.apache.org/licenses/LICENSE-2.0

	* Unless required by applicable law or agreed to in writing, software
	* distributed under the License is distributed on an "AS IS" BASIS,
	* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
	* See the License for the specific language governing permissions and
	* limitations under the License.
	*/
	package kvstore

	import (
	"context"
	"errors"
	"fmt"
	"github.com/opencord/voltha-go/common/log"
	v3Client "go.etcd.io/etcd/clientv3"
	v3Concurrency "go.etcd.io/etcd/clientv3/concurrency"
	v3rpcTypes "go.etcd.io/etcd/etcdserver/api/v3rpc/rpctypes"
	"sync"
	)

	// EtcdClient represents the Etcd KV store client
	type EtcdClient struct {
	ectdAPI *v3Client.Client
	leaderRev v3Client.Client
	keyReservations map[string]*v3Client.LeaseID
	watchedChannels map[string][]map[chan *Event]v3Client.Watcher
	writeLock sync.Mutex
	}

	// NewEtcdClient returns a new client for the Etcd KV store
	func NewEtcdClient(addr string, timeout int) (*EtcdClient, error) {
	duration := GetDuration(timeout)

	c, err := v3Client.New(v3Client.Config{
	Endpoints: []string{addr},
	DialTimeout: duration,
	})
	if err != nil {
	log.Error(err)
	return nil, err
	}
	wc := make(map[string][]map[chan *Event]v3Client.Watcher)
	reservations := make(map[string]*v3Client.LeaseID)

	return &EtcdClient{ectdAPI: c, watchedChannels: wc, keyReservations: reservations}, nil
	}

	// List returns an array of key-value pairs with key as a prefix. Timeout defines how long the function will
	// wait for a response
	func (c EtcdClient) List(key string, timeout int, lock ...bool) (map[string]KVPair, error) {
	duration := GetDuration(timeout)

	ctx, cancel := context.WithTimeout(context.Background(), duration)

	// DO NOT lock by default; otherwise lock per instructed value
	if len(lock) > 0 && lock[0] {
	session, _ := v3Concurrency.NewSession(c.ectdAPI, v3Concurrency.WithContext(ctx))
	mu := v3Concurrency.NewMutex(session, "/lock" + key)
	mu.Lock(context.Background())
	defer mu.Unlock(context.Background())
	defer session.Close()
	}

	resp, err := c.ectdAPI.Get(ctx, key, v3Client.WithPrefix())
	cancel()
	if err != nil {
	log.Error(err)
	return nil, err
	}
	m := make(map[string]*KVPair)
	for _, ev := range resp.Kvs {
	m[string(ev.Key)] = NewKVPair(string(ev.Key), ev.Value, "", ev.Lease)
	}
	return m, nil
	}

	// Get returns a key-value pair for a given key. Timeout defines how long the function will
	// wait for a response
	func (c EtcdClient) Get(key string, timeout int, lock ...bool) (KVPair, error) {
	duration := GetDuration(timeout)

	ctx, cancel := context.WithTimeout(context.Background(), duration)

	// Lock by default; otherwise lock per instructed value
	if len(lock) == 0 \|\| lock[0] {
	session, _ := v3Concurrency.NewSession(c.ectdAPI, v3Concurrency.WithContext(ctx))
	mu := v3Concurrency.NewMutex(session, "/lock" + key)
	mu.Lock(context.Background())
	defer mu.Unlock(context.Background())
	defer session.Close()
	}

	resp, err := c.ectdAPI.Get(ctx, key)
	cancel()
	if err != nil {
	log.Error(err)
	return nil, err
	}
	for _, ev := range resp.Kvs {
	// Only one value is returned
	return NewKVPair(string(ev.Key), ev.Value, "", ev.Lease), nil
	}
	return nil, nil
	}

	// Put writes a key-value pair to the KV store. Value can only be a string or []byte since the etcd API
	// accepts only a string as a value for a put operation. Timeout defines how long the function will
	// wait for a response
	func (c *EtcdClient) Put(key string, value interface{}, timeout int, lock ...bool) error {

	// Validate that we can convert value to a string as etcd API expects a string
	var val string
	var er error
	if val, er = ToString(value); er != nil {
	return fmt.Errorf("unexpected-type-%T", value)
	}

	duration := GetDuration(timeout)

	ctx, cancel := context.WithTimeout(context.Background(), duration)

	// Lock by default; otherwise lock per instructed value
	if len(lock) == 0 \|\| lock[0] {
	session, _ := v3Concurrency.NewSession(c.ectdAPI, v3Concurrency.WithContext(ctx))
	mu := v3Concurrency.NewMutex(session, "/lock" + key)
	mu.Lock(context.Background())
	defer mu.Unlock(context.Background())
	defer session.Close()
	}

	c.writeLock.Lock()
	defer c.writeLock.Unlock()
	_, err := c.ectdAPI.Put(ctx, key, val)
	cancel()
	if err != nil {
	switch err {
	case context.Canceled:
	log.Warnw("context-cancelled", log.Fields{"error": err})
	case context.DeadlineExceeded:
	log.Warnw("context-deadline-exceeded", log.Fields{"error": err})
	case v3rpcTypes.ErrEmptyKey:
	log.Warnw("etcd-client-error", log.Fields{"error": err})
	default:
	log.Warnw("bad-endpoints", log.Fields{"error": err})
	}
	return err
	}
	return nil
	}

	// Delete removes a key from the KV store. Timeout defines how long the function will
	// wait for a response
	func (c *EtcdClient) Delete(key string, timeout int, lock ...bool) error {

	duration := GetDuration(timeout)

	ctx, cancel := context.WithTimeout(context.Background(), duration)

	// Lock by default; otherwise lock per instructed value
	if len(lock) == 0 \|\| lock[0] {
	session, _ := v3Concurrency.NewSession(c.ectdAPI, v3Concurrency.WithContext(ctx))
	mu := v3Concurrency.NewMutex(session, "/lock" + key)
	mu.Lock(context.Background())
	defer mu.Unlock(context.Background())
	defer session.Close()
	}

	defer cancel()

	c.writeLock.Lock()
	defer c.writeLock.Unlock()

	// count keys about to be deleted
	gresp, err := c.ectdAPI.Get(ctx, key, v3Client.WithPrefix())
	if err != nil {
	log.Error(err)
	return err
	}

	// delete the keys
	dresp, err := c.ectdAPI.Delete(ctx, key, v3Client.WithPrefix())
	if err != nil {
	log.Error(err)
	return err
	}

	if dresp == nil \|\| gresp == nil {
	log.Debug("nothing-to-delete")
	return nil
	}

	log.Debugw("delete-keys", log.Fields{"all-keys-deleted": int64(len(gresp.Kvs)) == dresp.Deleted})
	if int64(len(gresp.Kvs)) == dresp.Deleted {
	log.Debug("All-keys-deleted")
	} else {
	log.Error("not-all-keys-deleted")
	err := errors.New("not-all-keys-deleted")
	return err
	}
	return nil
	}

	// Reserve is invoked to acquire a key and set it to a given value. Value can only be a string or []byte since
	// the etcd API accepts only a string. Timeout defines how long the function will wait for a response. TTL
	// defines how long that reservation is valid. When TTL expires the key is unreserved by the KV store itself.
	// If the key is acquired then the value returned will be the value passed in. If the key is already acquired
	// then the value assigned to that key will be returned.
	func (c *EtcdClient) Reserve(key string, value interface{}, ttl int64) (interface{}, error) {
	// Validate that we can convert value to a string as etcd API expects a string
	var val string
	var er error
	if val, er = ToString(value); er != nil {
	return nil, fmt.Errorf("unexpected-type%T", value)
	}

	// Create a lease
	resp, err := c.ectdAPI.Grant(context.Background(), ttl)
	if err != nil {
	log.Error(err)
	return nil, err
	}
	// Register the lease id
	c.writeLock.Lock()
	c.keyReservations[key] = &resp.ID
	c.writeLock.Unlock()

	// Revoke lease if reservation is not successful
	reservationSuccessful := false
	defer func() {
	if !reservationSuccessful {
	if err = c.ReleaseReservation(key); err != nil {
	log.Errorf("cannot-release-lease")
	}
	}
	}()

	// Try to grap the Key with the above lease
	c.ectdAPI.Txn(context.Background())
	txn := c.ectdAPI.Txn(context.Background())
	txn = txn.If(v3Client.Compare(v3Client.Version(key), "=", 0))
	txn = txn.Then(v3Client.OpPut(key, val, v3Client.WithLease(resp.ID)))
	txn = txn.Else(v3Client.OpGet(key))
	result, er := txn.Commit()
	if er != nil {
	return nil, er
	}

	if !result.Succeeded {
	// Verify whether we are already the owner of that Key
	if len(result.Responses) > 0 &&
	len(result.Responses[0].GetResponseRange().Kvs) > 0 {
	kv := result.Responses[0].GetResponseRange().Kvs[0]
	if string(kv.Value) == val {
	reservationSuccessful = true
	return value, nil
	}
	return kv.Value, nil
	}
	} else {
	// Read the Key to ensure this is our Key
	m, err := c.Get(key, defaultKVGetTimeout, false)
	if err != nil {
	return nil, err
	}
	if m != nil {
	if m.Key == key && isEqual(m.Value, value) {
	// My reservation is successful - register it. For now, support is only for 1 reservation per key
	// per session.
	reservationSuccessful = true
	return value, nil
	}
	// My reservation has failed. Return the owner of that key
	return m.Value, nil
	}
	}
	return nil, nil
	}

	// ReleaseAllReservations releases all key reservations previously made (using Reserve API)
	func (c *EtcdClient) ReleaseAllReservations() error {
	c.writeLock.Lock()
	defer c.writeLock.Unlock()
	for key, leaseID := range c.keyReservations {
	_, err := c.ectdAPI.Revoke(context.Background(), *leaseID)
	if err != nil {
	log.Errorw("cannot-release-reservation", log.Fields{"key": key, "error": err})
	return err
	}
	delete(c.keyReservations, key)
	}
	return nil
	}

	// ReleaseReservation releases reservation for a specific key.
	func (c *EtcdClient) ReleaseReservation(key string) error {
	// Get the leaseid using the key
	var ok bool
	var leaseID *v3Client.LeaseID
	c.writeLock.Lock()
	defer c.writeLock.Unlock()
	if leaseID, ok = c.keyReservations[key]; !ok {
	return errors.New("key-not-reserved")
	}
	if leaseID != nil {
	_, err := c.ectdAPI.Revoke(context.Background(), *leaseID)
	if err != nil {
	log.Error(err)
	return err
	}
	delete(c.keyReservations, key)
	}
	return nil
	}

	// RenewReservation renews a reservation. A reservation will go stale after the specified TTL (Time To Live)
	// period specified when reserving the key
	func (c *EtcdClient) RenewReservation(key string) error {
	// Get the leaseid using the key
	var ok bool
	var leaseID *v3Client.LeaseID
	c.writeLock.Lock()
	defer c.writeLock.Unlock()
	if leaseID, ok = c.keyReservations[key]; !ok {
	return errors.New("key-not-reserved")
	}

	if leaseID != nil {
	_, err := c.ectdAPI.KeepAliveOnce(context.Background(), *leaseID)
	if err != nil {
	log.Errorw("lease-may-have-expired", log.Fields{"error": err})
	return err
	}
	} else {
	return errors.New("lease-expired")
	}
	return nil
	}

	// Watch provides the watch capability on a given key. It returns a channel onto which the callee needs to
	// listen to receive Events.
	func (c EtcdClient) Watch(key string) chan Event {
	w := v3Client.NewWatcher(c.ectdAPI)
	channel := w.Watch(context.Background(), key, v3Client.WithPrefix())

	// Create a new channel
	ch := make(chan *Event, maxClientChannelBufferSize)

	// Keep track of the created channels so they can be closed when required
	channelMap := make(map[chan *Event]v3Client.Watcher)
	channelMap[ch] = w
	//c.writeLock.Lock()
	//defer c.writeLock.Unlock()
	c.watchedChannels[key] = append(c.watchedChannels[key], channelMap)

	log.Debugw("watched-channels", log.Fields{"channels": c.watchedChannels[key]})
	// Launch a go routine to listen for updates
	go c.listenForKeyChange(channel, ch)

	return ch

	}

	// CloseWatch closes a specific watch. Both the key and the channel are required when closing a watch as there
	// may be multiple listeners on the same key. The previously created channel serves as a key
	func (c EtcdClient) CloseWatch(key string, ch chan Event) {
	// Get the array of channels mapping
	var watchedChannels []map[chan *Event]v3Client.Watcher
	var ok bool
	c.writeLock.Lock()
	defer c.writeLock.Unlock()

	if watchedChannels, ok = c.watchedChannels[key]; !ok {
	log.Warnw("key-has-no-watched-channels", log.Fields{"key": key})
	return
	}
	// Look for the channels
	var pos = -1
	for i, chMap := range watchedChannels {
	if t, ok := chMap[ch]; ok {
	log.Debug("channel-found")
	// Close the etcd watcher before the client channel. This should close the etcd channel as well
	if err := t.Close(); err != nil {
	log.Errorw("watcher-cannot-be-closed", log.Fields{"key": key, "error": err})
	}
	close(ch)
	pos = i
	break
	}
	}
	// Remove that entry if present
	if pos >= 0 {
	c.watchedChannels[key] = append(c.watchedChannels[key][:pos], c.watchedChannels[key][pos+1:]...)
	}
	log.Infow("watcher-channel-exiting", log.Fields{"key": key, "channel": c.watchedChannels[key]})
	}

	func (c EtcdClient) listenForKeyChange(channel v3Client.WatchChan, ch chan<- Event) {
	log.Infow("start-listening-on-channel", log.Fields{"channel": ch})
	for resp := range channel {
	for _, ev := range resp.Events {
	//log.Debugf("%s %q : %q\n", ev.Type, ev.Kv.Key, ev.Kv.Value)
	ch <- NewEvent(getEventType(ev), ev.Kv.Key, ev.Kv.Value)
	}
	}
	log.Info("stop-listening-on-channel")
	}

	func getEventType(event *v3Client.Event) int {
	switch event.Type {
	case v3Client.EventTypePut:
	return PUT
	case v3Client.EventTypeDelete:
	return DELETE
	}
	return UNKNOWN
	}

	// Close closes the KV store client
	func (c *EtcdClient) Close() {
	c.writeLock.Lock()
	defer c.writeLock.Unlock()
	if err := c.ectdAPI.Close(); err != nil {
	log.Errorw("error-closing-client", log.Fields{"error": err})
	}
	}