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/*
* 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"
"sync"
"github.com/opencord/voltha-lib-go/v3/pkg/log"
v3Client "go.etcd.io/etcd/clientv3"
v3Concurrency "go.etcd.io/etcd/clientv3/concurrency"
v3rpcTypes "go.etcd.io/etcd/etcdserver/api/v3rpc/rpctypes"
)
// EtcdClient represents the Etcd KV store client
type EtcdClient struct {
ectdAPI *v3Client.Client
leaderRev v3Client.Client
keyReservations map[string]*v3Client.LeaseID
watchedChannels sync.Map
writeLock sync.Mutex
lockToMutexMap map[string]*v3Concurrency.Mutex
lockToSessionMap map[string]*v3Concurrency.Session
lockToMutexLock sync.Mutex
}
// Connection Timeout in Seconds
var connTimeout int = 2
// 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 {
logger.Error(err)
return nil, err
}
reservations := make(map[string]*v3Client.LeaseID)
lockMutexMap := make(map[string]*v3Concurrency.Mutex)
lockSessionMap := make(map[string]*v3Concurrency.Session)
return &EtcdClient{ectdAPI: c, keyReservations: reservations, lockToMutexMap: lockMutexMap,
lockToSessionMap: lockSessionMap}, nil
}
// 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
}
//cancel()
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) {
resp, err := c.ectdAPI.Get(ctx, key, v3Client.WithPrefix())
if err != nil {
logger.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, 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) {
resp, err := c.ectdAPI.Get(ctx, key)
if err != nil {
logger.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 er error
if val, er = ToString(value); er != nil {
return fmt.Errorf("unexpected-type-%T", value)
}
c.writeLock.Lock()
defer c.writeLock.Unlock()
var err error
// Check if there is already a lease for this key - if there is then use it, otherwise a PUT will make
// that KV key permanent instead of automatically removing it after a lease expiration
if leaseID, ok := c.keyReservations[key]; ok {
_, err = c.ectdAPI.Put(ctx, key, val, v3Client.WithLease(*leaseID))
} else {
_, err = c.ectdAPI.Put(ctx, key, val)
}
if err != nil {
switch err {
case context.Canceled:
logger.Warnw("context-cancelled", log.Fields{"error": err})
case context.DeadlineExceeded:
logger.Warnw("context-deadline-exceeded", log.Fields{"error": err})
case v3rpcTypes.ErrEmptyKey:
logger.Warnw("etcd-client-error", log.Fields{"error": err})
default:
logger.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(ctx context.Context, key string) error {
c.writeLock.Lock()
defer c.writeLock.Unlock()
// delete the key
if _, err := c.ectdAPI.Delete(ctx, key); err != nil {
logger.Errorw("failed-to-delete-key", log.Fields{"key": key, "error": err})
return err
}
logger.Debugw("key(s)-deleted", log.Fields{"key": key})
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(ctx context.Context, 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)
}
resp, err := c.ectdAPI.Grant(ctx, ttl)
if err != nil {
logger.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(context.Background(), key); err != nil {
logger.Error("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(ctx, key)
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(ctx context.Context) error {
c.writeLock.Lock()
defer c.writeLock.Unlock()
for key, leaseID := range c.keyReservations {
_, err := c.ectdAPI.Revoke(ctx, *leaseID)
if err != nil {
logger.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(ctx context.Context, key string) error {
// Get the leaseid using the key
logger.Debugw("Release-reservation", log.Fields{"key": key})
var ok bool
var leaseID *v3Client.LeaseID
c.writeLock.Lock()
defer c.writeLock.Unlock()
if leaseID, ok = c.keyReservations[key]; !ok {
return nil
}
if leaseID != nil {
_, err := c.ectdAPI.Revoke(ctx, *leaseID)
if err != nil {
logger.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(ctx context.Context, 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(ctx, *leaseID)
if err != nil {
logger.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(ctx context.Context, key string) chan *Event {
w := v3Client.NewWatcher(c.ectdAPI)
ctx, cancel := context.WithCancel(ctx)
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("watched-channels", log.Fields{"len": len(channelMaps)})
// Launch a go routine to listen for updates
go c.listenForKeyChange(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(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.getChannelMaps(key); !ok {
logger.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 {
logger.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 {
logger.Errorw("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)
}
logger.Infow("watcher-channel-exiting", log.Fields{"key": key, "channel": channelMaps})
}
func (c *EtcdClient) listenForKeyChange(channel v3Client.WatchChan, ch chan<- *Event, cancel context.CancelFunc) {
logger.Debug("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("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 {
logger.Errorw("error-closing-client", log.Fields{"error": err})
}
}
func (c *EtcdClient) addLockName(lockName string, lock *v3Concurrency.Mutex, session *v3Concurrency.Session) {
c.lockToMutexLock.Lock()
defer c.lockToMutexLock.Unlock()
c.lockToMutexMap[lockName] = lock
c.lockToSessionMap[lockName] = session
}
func (c *EtcdClient) deleteLockName(lockName string) {
c.lockToMutexLock.Lock()
defer c.lockToMutexLock.Unlock()
delete(c.lockToMutexMap, lockName)
delete(c.lockToSessionMap, lockName)
}
func (c *EtcdClient) getLock(lockName string) (*v3Concurrency.Mutex, *v3Concurrency.Session) {
c.lockToMutexLock.Lock()
defer c.lockToMutexLock.Unlock()
var lock *v3Concurrency.Mutex
var session *v3Concurrency.Session
if l, exist := c.lockToMutexMap[lockName]; exist {
lock = l
}
if s, exist := c.lockToSessionMap[lockName]; exist {
session = s
}
return lock, session
}
func (c *EtcdClient) AcquireLock(ctx context.Context, lockName string, timeout int) error {
session, _ := v3Concurrency.NewSession(c.ectdAPI, v3Concurrency.WithContext(ctx))
mu := v3Concurrency.NewMutex(session, "/devicelock_"+lockName)
if err := mu.Lock(context.Background()); err != nil {
//cancel()
return err
}
c.addLockName(lockName, mu, session)
return nil
}
func (c *EtcdClient) ReleaseLock(lockName string) error {
lock, session := c.getLock(lockName)
var err error
if lock != nil {
if e := lock.Unlock(context.Background()); e != nil {
err = e
}
}
if session != nil {
if e := session.Close(); e != nil {
err = e
}
}
c.deleteLockName(lockName)
return err
}