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

 /*
 * Copyright 2018-2023 Open Networking Foundation (ONF) and the ONF Contributors

 * 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"
 	"os"
 	"strconv"
 	"sync"
 	"time"

 	"github.com/opencord/voltha-lib-go/v7/pkg/log"
 	v3Client "go.etcd.io/etcd/clientv3"
 	v3rpcTypes "go.etcd.io/etcd/etcdserver/api/v3rpc/rpctypes"
 )

 const (
 	poolCapacityEnvName = "VOLTHA_ETCD_CLIENT_POOL_CAPACITY"
 	maxUsageEnvName     = "VOLTHA_ETCD_CLIENT_MAX_USAGE"
 )

 const (
 	defaultMaxPoolCapacity = 1000 // Default size of an Etcd Client pool
 	defaultMaxPoolUsage    = 100  // Maximum concurrent request an Etcd Client is allowed to process
 )

 // EtcdClient represents the Etcd KV store client
 type EtcdClient struct {
 	pool               EtcdClientAllocator
 	watchedChannels    sync.Map
 	watchedClients     map[string]*v3Client.Client
 	watchedClientsLock sync.RWMutex
 }

 // NewEtcdCustomClient returns a new client for the Etcd KV store allowing
 // the called to specify etcd client configuration
 func NewEtcdCustomClient(ctx context.Context, addr string, timeout time.Duration, level log.LogLevel) (*EtcdClient, error) {
 	// Get the capacity and max usage from the environment
 	capacity := defaultMaxPoolCapacity
 	maxUsage := defaultMaxPoolUsage
 	if capacityStr, present := os.LookupEnv(poolCapacityEnvName); present {
 		if val, err := strconv.Atoi(capacityStr); err == nil {
 			capacity = val
 			logger.Infow(ctx, "env-variable-set", log.Fields{"pool-capacity": capacity})
 		} else {
 			logger.Warnw(ctx, "invalid-capacity-value", log.Fields{"error": err, "capacity": capacityStr})
 		}
 	}
 	if maxUsageStr, present := os.LookupEnv(maxUsageEnvName); present {
 		if val, err := strconv.Atoi(maxUsageStr); err == nil {
 			maxUsage = val
 			logger.Infow(ctx, "env-variable-set", log.Fields{"max-usage": maxUsage})
 		} else {
 			logger.Warnw(ctx, "invalid-max-usage-value", log.Fields{"error": err, "max-usage": maxUsageStr})
 		}
 	}

 	var err error

 	pool, err := NewRoundRobinEtcdClientAllocator([]string{addr}, timeout, capacity, maxUsage, level)
 	if err != nil {
 		logger.Errorw(ctx, "failed-to-create-rr-client", log.Fields{
 			"error": err,
 		})
 	}

 	logger.Infow(ctx, "etcd-pool-created", log.Fields{"capacity": capacity, "max-usage": maxUsage})

 	return &EtcdClient{pool: pool,
 		watchedClients: make(map[string]*v3Client.Client),
 	}, nil
 }

 // NewEtcdClient returns a new client for the Etcd KV store
 func NewEtcdClient(ctx context.Context, addr string, timeout time.Duration, level log.LogLevel) (*EtcdClient, error) {
 	return NewEtcdCustomClient(ctx, addr, timeout, level)
 }

 // IsConnectionUp returns whether the connection to the Etcd KV store is up.  If a timeout occurs then
 // it is assumed the connection is down or unreachable.
 func (c *EtcdClient) IsConnectionUp(ctx context.Context) bool {
 	// Let's try to get a non existent key.  If the connection is up then there will be no error returned.
 	if _, err := c.Get(ctx, "non-existent-key"); err != nil {
 		return false
 	}
 	return true
 }

 // 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(ctx context.Context, key string) (map[string]*KVPair, error) {
 	client, err := c.pool.Get(ctx)
 	if err != nil {
 		return nil, err
 	}
 	defer c.pool.Put(client)
 	resp, err := client.Get(ctx, key, v3Client.WithPrefix())

 	if err != nil {
 		logger.Error(ctx, 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, ev.Version)
 	}
 	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(ctx context.Context, key string) (*KVPair, error) {
 	client, err := c.pool.Get(ctx)
 	if err != nil {
 		return nil, err
 	}
 	defer c.pool.Put(client)

 	attempt := 0

 startLoop:
 	for {
 		resp, err := client.Get(ctx, key)
 		if err != nil {
 			switch err {
 			case context.Canceled:
 				logger.Warnw(ctx, "context-cancelled", log.Fields{"error": err})
 			case context.DeadlineExceeded:
 				logger.Warnw(ctx, "context-deadline-exceeded", log.Fields{"error": err, "context": ctx})
 			case v3rpcTypes.ErrEmptyKey:
 				logger.Warnw(ctx, "etcd-client-error", log.Fields{"error": err})
 			case v3rpcTypes.ErrLeaderChanged,
 				v3rpcTypes.ErrGRPCNoLeader,
 				v3rpcTypes.ErrTimeout,
 				v3rpcTypes.ErrTimeoutDueToLeaderFail,
 				v3rpcTypes.ErrTimeoutDueToConnectionLost:
 				// Retry for these server errors
 				attempt += 1
 				if er := backoff(ctx, attempt); er != nil {
 					logger.Warnw(ctx, "get-retries-failed", log.Fields{"key": key, "error": er, "attempt": attempt})
 					return nil, err
 				}
 				logger.Warnw(ctx, "retrying-get", log.Fields{"key": key, "error": err, "attempt": attempt})
 				goto startLoop
 			default:
 				logger.Warnw(ctx, "etcd-server-error", log.Fields{"error": err})
 			}
 			return nil, err
 		}

 		for _, ev := range resp.Kvs {
 			// Only one value is returned
 			return NewKVPair(string(ev.Key), ev.Value, "", ev.Lease, ev.Version), 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(ctx context.Context, key string, value interface{}) error {

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

 	client, err := c.pool.Get(ctx)
 	if err != nil {
 		return err
 	}
 	defer c.pool.Put(client)

 	attempt := 0
 startLoop:
 	for {
 		_, err = client.Put(ctx, key, val)
 		if err != nil {
 			switch err {
 			case context.Canceled:
 				logger.Warnw(ctx, "context-cancelled", log.Fields{"error": err})
 			case context.DeadlineExceeded:
 				logger.Warnw(ctx, "context-deadline-exceeded", log.Fields{"error": err, "context": ctx})
 			case v3rpcTypes.ErrEmptyKey:
 				logger.Warnw(ctx, "etcd-client-error", log.Fields{"error": err})
 			case v3rpcTypes.ErrLeaderChanged,
 				v3rpcTypes.ErrGRPCNoLeader,
 				v3rpcTypes.ErrTimeout,
 				v3rpcTypes.ErrTimeoutDueToLeaderFail,
 				v3rpcTypes.ErrTimeoutDueToConnectionLost:
 				// Retry for these server errors
 				attempt += 1
 				if er := backoff(ctx, attempt); er != nil {
 					logger.Warnw(ctx, "put-retries-failed", log.Fields{"key": key, "error": er, "attempt": attempt})
 					return err
 				}
 				logger.Warnw(ctx, "retrying-put", log.Fields{"key": key, "error": err, "attempt": attempt})
 				goto startLoop
 			default:
 				logger.Warnw(ctx, "etcd-server-error", 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(ctx context.Context, key string) error {
 	client, err := c.pool.Get(ctx)
 	if err != nil {
 		return err
 	}
 	defer c.pool.Put(client)

 	attempt := 0
 startLoop:
 	for {
 		_, err = client.Delete(ctx, key)
 		if err != nil {
 			switch err {
 			case context.Canceled:
 				logger.Warnw(ctx, "context-cancelled", log.Fields{"error": err})
 			case context.DeadlineExceeded:
 				logger.Warnw(ctx, "context-deadline-exceeded", log.Fields{"error": err, "context": ctx})
 			case v3rpcTypes.ErrEmptyKey:
 				logger.Warnw(ctx, "etcd-client-error", log.Fields{"error": err})
 			case v3rpcTypes.ErrLeaderChanged,
 				v3rpcTypes.ErrGRPCNoLeader,
 				v3rpcTypes.ErrTimeout,
 				v3rpcTypes.ErrTimeoutDueToLeaderFail,
 				v3rpcTypes.ErrTimeoutDueToConnectionLost:
 				// Retry for these server errors
 				attempt += 1
 				if er := backoff(ctx, attempt); er != nil {
 					logger.Warnw(ctx, "delete-retries-failed", log.Fields{"key": key, "error": er, "attempt": attempt})
 					return err
 				}
 				logger.Warnw(ctx, "retrying-delete", log.Fields{"key": key, "error": err, "attempt": attempt})
 				goto startLoop
 			default:
 				logger.Warnw(ctx, "etcd-server-error", log.Fields{"error": err})
 			}
 			return err
 		}
 		logger.Debugw(ctx, "key(s)-deleted", log.Fields{"key": key})
 		return nil
 	}
 }

 func (c *EtcdClient) DeleteWithPrefix(ctx context.Context, prefixKey string) error {

 	client, err := c.pool.Get(ctx)
 	if err != nil {
 		return err
 	}
 	defer c.pool.Put(client)

 	//delete the prefix
 	if _, err := client.Delete(ctx, prefixKey, v3Client.WithPrefix()); err != nil {
 		logger.Errorw(ctx, "failed-to-delete-prefix-key", log.Fields{"key": prefixKey, "error": err})
 		return err
 	}
 	logger.Debugw(ctx, "key(s)-deleted", log.Fields{"key": prefixKey})
 	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(ctx context.Context, key string, withPrefix bool) chan *Event {
 	var err error
 	// Reuse the Etcd client when multiple callees are watching the same key.
 	c.watchedClientsLock.Lock()
 	client, exist := c.watchedClients[key]
 	if !exist {
 		client, err = c.pool.Get(ctx)
 		if err != nil {
 			logger.Errorw(ctx, "failed-to-an-etcd-client", log.Fields{"key": key, "error": err})
 			c.watchedClientsLock.Unlock()
 			return nil
 		}
 		c.watchedClients[key] = client
 	}
 	c.watchedClientsLock.Unlock()

 	w := v3Client.NewWatcher(client)
 	ctx, cancel := context.WithCancel(ctx)
 	var channel v3Client.WatchChan
 	if withPrefix {
 		channel = w.Watch(ctx, key, v3Client.WithPrefix())
 	} else {
 		channel = w.Watch(ctx, key)
 	}

 	// 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
 	channelMaps := c.addChannelMap(key, channelMap)

 	// Changing the log field (from channelMaps) as the underlying logger cannot format the map of channels into a
 	// json format.
 	logger.Debugw(ctx, "watched-channels", log.Fields{"len": len(channelMaps)})
 	// Launch a go routine to listen for updates
 	go c.listenForKeyChange(ctx, channel, ch, cancel)

 	return ch

 }

 func (c *EtcdClient) addChannelMap(key string, channelMap map[chan *Event]v3Client.Watcher) []map[chan *Event]v3Client.Watcher {
 	var channels interface{}
 	var exists bool

 	if channels, exists = c.watchedChannels.Load(key); exists {
 		channels = append(channels.([]map[chan *Event]v3Client.Watcher), channelMap)
 	} else {
 		channels = []map[chan *Event]v3Client.Watcher{channelMap}
 	}
 	c.watchedChannels.Store(key, channels)

 	return channels.([]map[chan *Event]v3Client.Watcher)
 }

 func (c *EtcdClient) removeChannelMap(key string, pos int) []map[chan *Event]v3Client.Watcher {
 	var channels interface{}
 	var exists bool

 	if channels, exists = c.watchedChannels.Load(key); exists {
 		channels = append(channels.([]map[chan *Event]v3Client.Watcher)[:pos], channels.([]map[chan *Event]v3Client.Watcher)[pos+1:]...)
 		c.watchedChannels.Store(key, channels)
 	}

 	return channels.([]map[chan *Event]v3Client.Watcher)
 }

 func (c *EtcdClient) getChannelMaps(key string) ([]map[chan *Event]v3Client.Watcher, bool) {
 	var channels interface{}
 	var exists bool

 	channels, exists = c.watchedChannels.Load(key)

 	if channels == nil {
 		return nil, exists
 	}

 	return channels.([]map[chan *Event]v3Client.Watcher), exists
 }

 // 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(ctx context.Context, key string, ch chan *Event) {
 	// Get the array of channels mapping
 	var watchedChannels []map[chan *Event]v3Client.Watcher
 	var ok bool

 	if watchedChannels, ok = c.getChannelMaps(key); !ok {
 		logger.Warnw(ctx, "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 {
 			logger.Debug(ctx, "channel-found")
 			// Close the etcd watcher before the client channel.  This should close the etcd channel as well
 			if err := t.Close(); err != nil {
 				logger.Errorw(ctx, "watcher-cannot-be-closed", log.Fields{"key": key, "error": err})
 			}
 			pos = i
 			break
 		}
 	}

 	channelMaps, _ := c.getChannelMaps(key)
 	// Remove that entry if present
 	if pos >= 0 {
 		channelMaps = c.removeChannelMap(key, pos)
 	}

 	// If we don't have any keys being watched then return the Etcd client to the pool
 	if len(channelMaps) == 0 {
 		c.watchedClientsLock.Lock()
 		// Sanity
 		if client, ok := c.watchedClients[key]; ok {
 			c.pool.Put(client)
 			delete(c.watchedClients, key)
 		}
 		c.watchedClientsLock.Unlock()
 	}
 	logger.Infow(ctx, "watcher-channel-exiting", log.Fields{"key": key, "channel": channelMaps})
 }

 func (c *EtcdClient) listenForKeyChange(ctx context.Context, channel v3Client.WatchChan, ch chan<- *Event, cancel context.CancelFunc) {
 	logger.Debug(ctx, "start-listening-on-channel ...")
 	defer cancel()
 	defer close(ch)
 	for resp := range channel {
 		for _, ev := range resp.Events {
 			ch <- NewEvent(getEventType(ev), ev.Kv.Key, ev.Kv.Value, ev.Kv.Version)
 		}
 	}
 	logger.Debug(ctx, "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 all the connection in the pool store client
 func (c *EtcdClient) Close(ctx context.Context) {
 	logger.Debug(ctx, "closing-etcd-pool")
 	c.pool.Close(ctx)
 }

 // The APIs below are not used
 var errUnimplemented = errors.New("deprecated")

 // Reserve is deprecated
 func (c *EtcdClient) Reserve(ctx context.Context, key string, value interface{}, ttl time.Duration) (interface{}, error) {
 	return nil, errUnimplemented
 }

 // ReleaseAllReservations is deprecated
 func (c *EtcdClient) ReleaseAllReservations(ctx context.Context) error {
 	return errUnimplemented
 }

 // ReleaseReservation is deprecated
 func (c *EtcdClient) ReleaseReservation(ctx context.Context, key string) error {
 	return errUnimplemented
 }

 // RenewReservation is deprecated
 func (c *EtcdClient) RenewReservation(ctx context.Context, key string) error {
 	return errUnimplemented
 }

 // AcquireLock is deprecated
 func (c *EtcdClient) AcquireLock(ctx context.Context, lockName string, timeout time.Duration) error {
 	return errUnimplemented
 }

 // ReleaseLock is deprecated
 func (c *EtcdClient) ReleaseLock(lockName string) error {
 	return errUnimplemented
 }
	/*
	* Copyright 2018-2023 Open Networking Foundation (ONF) and the ONF Contributors

	* 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"
	"os"
	"strconv"
	"sync"
	"time"

	"github.com/opencord/voltha-lib-go/v7/pkg/log"
	v3Client "go.etcd.io/etcd/clientv3"
	v3rpcTypes "go.etcd.io/etcd/etcdserver/api/v3rpc/rpctypes"
	)

	const (
	poolCapacityEnvName = "VOLTHA_ETCD_CLIENT_POOL_CAPACITY"
	maxUsageEnvName = "VOLTHA_ETCD_CLIENT_MAX_USAGE"
	)

	const (
	defaultMaxPoolCapacity = 1000 // Default size of an Etcd Client pool
	defaultMaxPoolUsage = 100 // Maximum concurrent request an Etcd Client is allowed to process
	)

	// EtcdClient represents the Etcd KV store client
	type EtcdClient struct {
	pool EtcdClientAllocator
	watchedChannels sync.Map
	watchedClients map[string]*v3Client.Client
	watchedClientsLock sync.RWMutex
	}

	// NewEtcdCustomClient returns a new client for the Etcd KV store allowing
	// the called to specify etcd client configuration
	func NewEtcdCustomClient(ctx context.Context, addr string, timeout time.Duration, level log.LogLevel) (*EtcdClient, error) {
	// Get the capacity and max usage from the environment
	capacity := defaultMaxPoolCapacity
	maxUsage := defaultMaxPoolUsage
	if capacityStr, present := os.LookupEnv(poolCapacityEnvName); present {
	if val, err := strconv.Atoi(capacityStr); err == nil {
	capacity = val
	logger.Infow(ctx, "env-variable-set", log.Fields{"pool-capacity": capacity})
	} else {
	logger.Warnw(ctx, "invalid-capacity-value", log.Fields{"error": err, "capacity": capacityStr})
	}
	}
	if maxUsageStr, present := os.LookupEnv(maxUsageEnvName); present {
	if val, err := strconv.Atoi(maxUsageStr); err == nil {
	maxUsage = val
	logger.Infow(ctx, "env-variable-set", log.Fields{"max-usage": maxUsage})
	} else {
	logger.Warnw(ctx, "invalid-max-usage-value", log.Fields{"error": err, "max-usage": maxUsageStr})
	}
	}

	var err error

	pool, err := NewRoundRobinEtcdClientAllocator([]string{addr}, timeout, capacity, maxUsage, level)
	if err != nil {
	logger.Errorw(ctx, "failed-to-create-rr-client", log.Fields{
	"error": err,
	})
	}

	logger.Infow(ctx, "etcd-pool-created", log.Fields{"capacity": capacity, "max-usage": maxUsage})

	return &EtcdClient{pool: pool,
	watchedClients: make(map[string]*v3Client.Client),
	}, nil
	}

	// NewEtcdClient returns a new client for the Etcd KV store
	func NewEtcdClient(ctx context.Context, addr string, timeout time.Duration, level log.LogLevel) (*EtcdClient, error) {
	return NewEtcdCustomClient(ctx, addr, timeout, level)
	}

	// IsConnectionUp returns whether the connection to the Etcd KV store is up. If a timeout occurs then
	// it is assumed the connection is down or unreachable.
	func (c *EtcdClient) IsConnectionUp(ctx context.Context) bool {
	// Let's try to get a non existent key. If the connection is up then there will be no error returned.
	if _, err := c.Get(ctx, "non-existent-key"); err != nil {
	return false
	}
	return true
	}

	// 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(ctx context.Context, key string) (map[string]KVPair, error) {
	client, err := c.pool.Get(ctx)
	if err != nil {
	return nil, err
	}
	defer c.pool.Put(client)
	resp, err := client.Get(ctx, key, v3Client.WithPrefix())

	if err != nil {
	logger.Error(ctx, 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, ev.Version)
	}
	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(ctx context.Context, key string) (KVPair, error) {
	client, err := c.pool.Get(ctx)
	if err != nil {
	return nil, err
	}
	defer c.pool.Put(client)

	attempt := 0

	startLoop:
	for {
	resp, err := client.Get(ctx, key)
	if err != nil {
	switch err {
	case context.Canceled:
	logger.Warnw(ctx, "context-cancelled", log.Fields{"error": err})
	case context.DeadlineExceeded:
	logger.Warnw(ctx, "context-deadline-exceeded", log.Fields{"error": err, "context": ctx})
	case v3rpcTypes.ErrEmptyKey:
	logger.Warnw(ctx, "etcd-client-error", log.Fields{"error": err})
	case v3rpcTypes.ErrLeaderChanged,
	v3rpcTypes.ErrGRPCNoLeader,
	v3rpcTypes.ErrTimeout,
	v3rpcTypes.ErrTimeoutDueToLeaderFail,
	v3rpcTypes.ErrTimeoutDueToConnectionLost:
	// Retry for these server errors
	attempt += 1
	if er := backoff(ctx, attempt); er != nil {
	logger.Warnw(ctx, "get-retries-failed", log.Fields{"key": key, "error": er, "attempt": attempt})
	return nil, err
	}
	logger.Warnw(ctx, "retrying-get", log.Fields{"key": key, "error": err, "attempt": attempt})
	goto startLoop
	default:
	logger.Warnw(ctx, "etcd-server-error", log.Fields{"error": err})
	}
	return nil, err
	}

	for _, ev := range resp.Kvs {
	// Only one value is returned
	return NewKVPair(string(ev.Key), ev.Value, "", ev.Lease, ev.Version), 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(ctx context.Context, key string, value interface{}) error {

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

	client, err := c.pool.Get(ctx)
	if err != nil {
	return err
	}
	defer c.pool.Put(client)

	attempt := 0
	startLoop:
	for {
	_, err = client.Put(ctx, key, val)
	if err != nil {
	switch err {
	case context.Canceled:
	logger.Warnw(ctx, "context-cancelled", log.Fields{"error": err})
	case context.DeadlineExceeded:
	logger.Warnw(ctx, "context-deadline-exceeded", log.Fields{"error": err, "context": ctx})
	case v3rpcTypes.ErrEmptyKey:
	logger.Warnw(ctx, "etcd-client-error", log.Fields{"error": err})
	case v3rpcTypes.ErrLeaderChanged,
	v3rpcTypes.ErrGRPCNoLeader,
	v3rpcTypes.ErrTimeout,
	v3rpcTypes.ErrTimeoutDueToLeaderFail,
	v3rpcTypes.ErrTimeoutDueToConnectionLost:
	// Retry for these server errors
	attempt += 1
	if er := backoff(ctx, attempt); er != nil {
	logger.Warnw(ctx, "put-retries-failed", log.Fields{"key": key, "error": er, "attempt": attempt})
	return err
	}
	logger.Warnw(ctx, "retrying-put", log.Fields{"key": key, "error": err, "attempt": attempt})
	goto startLoop
	default:
	logger.Warnw(ctx, "etcd-server-error", 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(ctx context.Context, key string) error {
	client, err := c.pool.Get(ctx)
	if err != nil {
	return err
	}
	defer c.pool.Put(client)

	attempt := 0
	startLoop:
	for {
	_, err = client.Delete(ctx, key)
	if err != nil {
	switch err {
	case context.Canceled:
	logger.Warnw(ctx, "context-cancelled", log.Fields{"error": err})
	case context.DeadlineExceeded:
	logger.Warnw(ctx, "context-deadline-exceeded", log.Fields{"error": err, "context": ctx})
	case v3rpcTypes.ErrEmptyKey:
	logger.Warnw(ctx, "etcd-client-error", log.Fields{"error": err})
	case v3rpcTypes.ErrLeaderChanged,
	v3rpcTypes.ErrGRPCNoLeader,
	v3rpcTypes.ErrTimeout,
	v3rpcTypes.ErrTimeoutDueToLeaderFail,
	v3rpcTypes.ErrTimeoutDueToConnectionLost:
	// Retry for these server errors
	attempt += 1
	if er := backoff(ctx, attempt); er != nil {
	logger.Warnw(ctx, "delete-retries-failed", log.Fields{"key": key, "error": er, "attempt": attempt})
	return err
	}
	logger.Warnw(ctx, "retrying-delete", log.Fields{"key": key, "error": err, "attempt": attempt})
	goto startLoop
	default:
	logger.Warnw(ctx, "etcd-server-error", log.Fields{"error": err})
	}
	return err
	}
	logger.Debugw(ctx, "key(s)-deleted", log.Fields{"key": key})
	return nil
	}
	}

	func (c *EtcdClient) DeleteWithPrefix(ctx context.Context, prefixKey string) error {

	client, err := c.pool.Get(ctx)
	if err != nil {
	return err
	}
	defer c.pool.Put(client)

	//delete the prefix
	if _, err := client.Delete(ctx, prefixKey, v3Client.WithPrefix()); err != nil {
	logger.Errorw(ctx, "failed-to-delete-prefix-key", log.Fields{"key": prefixKey, "error": err})
	return err
	}
	logger.Debugw(ctx, "key(s)-deleted", log.Fields{"key": prefixKey})
	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(ctx context.Context, key string, withPrefix bool) chan Event {
	var err error
	// Reuse the Etcd client when multiple callees are watching the same key.
	c.watchedClientsLock.Lock()
	client, exist := c.watchedClients[key]
	if !exist {
	client, err = c.pool.Get(ctx)
	if err != nil {
	logger.Errorw(ctx, "failed-to-an-etcd-client", log.Fields{"key": key, "error": err})
	c.watchedClientsLock.Unlock()
	return nil
	}
	c.watchedClients[key] = client
	}
	c.watchedClientsLock.Unlock()

	w := v3Client.NewWatcher(client)
	ctx, cancel := context.WithCancel(ctx)
	var channel v3Client.WatchChan
	if withPrefix {
	channel = w.Watch(ctx, key, v3Client.WithPrefix())
	} else {
	channel = w.Watch(ctx, key)
	}

	// 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
	channelMaps := c.addChannelMap(key, channelMap)

	// Changing the log field (from channelMaps) as the underlying logger cannot format the map of channels into a
	// json format.
	logger.Debugw(ctx, "watched-channels", log.Fields{"len": len(channelMaps)})
	// Launch a go routine to listen for updates
	go c.listenForKeyChange(ctx, channel, ch, cancel)

	return ch

	}

	func (c EtcdClient) addChannelMap(key string, channelMap map[chan Event]v3Client.Watcher) []map[chan *Event]v3Client.Watcher {
	var channels interface{}
	var exists bool

	if channels, exists = c.watchedChannels.Load(key); exists {
	channels = append(channels.([]map[chan *Event]v3Client.Watcher), channelMap)
	} else {
	channels = []map[chan *Event]v3Client.Watcher{channelMap}
	}
	c.watchedChannels.Store(key, channels)

	return channels.([]map[chan *Event]v3Client.Watcher)
	}

	func (c EtcdClient) removeChannelMap(key string, pos int) []map[chan Event]v3Client.Watcher {
	var channels interface{}
	var exists bool

	if channels, exists = c.watchedChannels.Load(key); exists {
	channels = append(channels.([]map[chan Event]v3Client.Watcher)[:pos], channels.([]map[chan Event]v3Client.Watcher)[pos+1:]...)
	c.watchedChannels.Store(key, channels)
	}

	return channels.([]map[chan *Event]v3Client.Watcher)
	}

	func (c EtcdClient) getChannelMaps(key string) ([]map[chan Event]v3Client.Watcher, bool) {
	var channels interface{}
	var exists bool

	channels, exists = c.watchedChannels.Load(key)

	if channels == nil {
	return nil, exists
	}

	return channels.([]map[chan *Event]v3Client.Watcher), exists
	}

	// 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(ctx context.Context, key string, ch chan Event) {
	// Get the array of channels mapping
	var watchedChannels []map[chan *Event]v3Client.Watcher
	var ok bool

	if watchedChannels, ok = c.getChannelMaps(key); !ok {
	logger.Warnw(ctx, "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 {
	logger.Debug(ctx, "channel-found")
	// Close the etcd watcher before the client channel. This should close the etcd channel as well
	if err := t.Close(); err != nil {
	logger.Errorw(ctx, "watcher-cannot-be-closed", log.Fields{"key": key, "error": err})
	}
	pos = i
	break
	}
	}

	channelMaps, _ := c.getChannelMaps(key)
	// Remove that entry if present
	if pos >= 0 {
	channelMaps = c.removeChannelMap(key, pos)
	}

	// If we don't have any keys being watched then return the Etcd client to the pool
	if len(channelMaps) == 0 {
	c.watchedClientsLock.Lock()
	// Sanity
	if client, ok := c.watchedClients[key]; ok {
	c.pool.Put(client)
	delete(c.watchedClients, key)
	}
	c.watchedClientsLock.Unlock()
	}
	logger.Infow(ctx, "watcher-channel-exiting", log.Fields{"key": key, "channel": channelMaps})
	}

	func (c EtcdClient) listenForKeyChange(ctx context.Context, channel v3Client.WatchChan, ch chan<- Event, cancel context.CancelFunc) {
	logger.Debug(ctx, "start-listening-on-channel ...")
	defer cancel()
	defer close(ch)
	for resp := range channel {
	for _, ev := range resp.Events {
	ch <- NewEvent(getEventType(ev), ev.Kv.Key, ev.Kv.Value, ev.Kv.Version)
	}
	}
	logger.Debug(ctx, "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 all the connection in the pool store client
	func (c *EtcdClient) Close(ctx context.Context) {
	logger.Debug(ctx, "closing-etcd-pool")
	c.pool.Close(ctx)
	}

	// The APIs below are not used
	var errUnimplemented = errors.New("deprecated")

	// Reserve is deprecated
	func (c *EtcdClient) Reserve(ctx context.Context, key string, value interface{}, ttl time.Duration) (interface{}, error) {
	return nil, errUnimplemented
	}

	// ReleaseAllReservations is deprecated
	func (c *EtcdClient) ReleaseAllReservations(ctx context.Context) error {
	return errUnimplemented
	}

	// ReleaseReservation is deprecated
	func (c *EtcdClient) ReleaseReservation(ctx context.Context, key string) error {
	return errUnimplemented
	}

	// RenewReservation is deprecated
	func (c *EtcdClient) RenewReservation(ctx context.Context, key string) error {
	return errUnimplemented
	}

	// AcquireLock is deprecated
	func (c *EtcdClient) AcquireLock(ctx context.Context, lockName string, timeout time.Duration) error {
	return errUnimplemented
	}

	// ReleaseLock is deprecated
	func (c *EtcdClient) ReleaseLock(lockName string) error {
	return errUnimplemented
	}