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consul.go
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consul.go
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package store
import (
"crypto/tls"
"net/http"
"strings"
"sync"
"time"
log "github.com/Sirupsen/logrus"
api "github.com/hashicorp/consul/api"
)
const (
// DefaultWatchWaitTime is how long we block for at a time to check if the
// watched key has changed. This affects the minimum time it takes to
// cancel a watch.
DefaultWatchWaitTime = 15 * time.Second
)
// Consul embeds the client and watches
type Consul struct {
sync.Mutex
config *api.Config
client *api.Client
ephemeralTTL time.Duration
ephemeralSession string
}
type consulLock struct {
lock *api.Lock
}
// InitializeConsul creates a new Consul client given
// a list of endpoints and optional tls config
func InitializeConsul(endpoints []string, options *Config) (Store, error) {
s := &Consul{}
// Create Consul client
config := api.DefaultConfig()
s.config = config
config.HttpClient = http.DefaultClient
config.Address = endpoints[0]
config.Scheme = "http"
// Set options
if options != nil {
if options.TLS != nil {
s.setTLS(options.TLS)
}
if options.ConnectionTimeout != 0 {
s.setTimeout(options.ConnectionTimeout)
}
if options.EphemeralTTL != 0 {
s.setEphemeralTTL(options.EphemeralTTL)
}
}
// Creates a new client
client, err := api.NewClient(config)
if err != nil {
log.Errorf("Couldn't initialize consul client..")
return nil, err
}
s.client = client
return s, nil
}
// SetTLS sets Consul TLS options
func (s *Consul) setTLS(tls *tls.Config) {
s.config.HttpClient.Transport = &http.Transport{
TLSClientConfig: tls,
}
s.config.Scheme = "https"
}
// SetTimeout sets the timout for connecting to Consul
func (s *Consul) setTimeout(time time.Duration) {
s.config.WaitTime = time
}
// SetEphemeralTTL sets the ttl for ephemeral nodes
func (s *Consul) setEphemeralTTL(ttl time.Duration) {
s.ephemeralTTL = ttl
}
// createEphemeralSession creates the global session
// once that is used to delete keys at node failure
func (s *Consul) createEphemeralSession() error {
s.Lock()
defer s.Unlock()
// Create new session
if s.ephemeralSession == "" {
entry := &api.SessionEntry{
Behavior: api.SessionBehaviorDelete,
TTL: s.ephemeralTTL.String(),
}
// Create global ephemeral keys session
session, _, err := s.client.Session().Create(entry, nil)
if err != nil {
return err
}
s.ephemeralSession = session
}
return nil
}
// checkActiveSession checks if the key already has a session attached
func (s *Consul) checkActiveSession(key string) (string, error) {
pair, _, err := s.client.KV().Get(key, nil)
if err != nil {
return "", err
}
if pair != nil && pair.Session != "" {
return pair.Session, nil
}
return "", nil
}
// Normalize the key for usage in Consul
func (s *Consul) normalize(key string) string {
key = normalize(key)
return strings.TrimPrefix(key, "/")
}
// Get the value at "key", returns the last modified index
// to use in conjunction to CAS calls
func (s *Consul) Get(key string) (*KVPair, error) {
options := &api.QueryOptions{
AllowStale: false,
RequireConsistent: true,
}
pair, meta, err := s.client.KV().Get(s.normalize(key), options)
if err != nil {
return nil, err
}
if pair == nil {
return nil, ErrKeyNotFound
}
return &KVPair{pair.Key, pair.Value, meta.LastIndex}, nil
}
// Put a value at "key"
func (s *Consul) Put(key string, value []byte, opts *WriteOptions) error {
key = s.normalize(key)
p := &api.KVPair{
Key: key,
Value: value,
}
if opts != nil && opts.Ephemeral {
// Check if there is any previous session with an active TTL
previous, err := s.checkActiveSession(key)
if err != nil {
return err
}
// Create the global ephemeral session if it does not exist yet
if s.ephemeralSession == "" {
if err = s.createEphemeralSession(); err != nil {
return err
}
}
// If a previous session is still active for that key, use it
// else we use the global ephemeral session
if previous != "" {
p.Session = previous
} else {
p.Session = s.ephemeralSession
}
// Create lock option with the
// EphemeralSession
lockOpts := &api.LockOptions{
Key: key,
Session: p.Session,
}
// Lock and ignore if lock is held
// It's just a placeholder for the
// ephemeral behavior
lock, _ := s.client.LockOpts(lockOpts)
if lock != nil {
lock.Lock(nil)
}
// Renew the session
_, _, err = s.client.Session().Renew(p.Session, nil)
if err != nil {
s.ephemeralSession = ""
return err
}
}
_, err := s.client.KV().Put(p, nil)
return err
}
// Delete a value at "key"
func (s *Consul) Delete(key string) error {
_, err := s.client.KV().Delete(s.normalize(key), nil)
return err
}
// Exists checks that the key exists inside the store
func (s *Consul) Exists(key string) (bool, error) {
_, err := s.Get(key)
if err != nil && err == ErrKeyNotFound {
return false, err
}
return true, nil
}
// List the content of a given prefix
func (s *Consul) List(prefix string) ([]*KVPair, error) {
pairs, _, err := s.client.KV().List(s.normalize(prefix), nil)
if err != nil {
return nil, err
}
if len(pairs) == 0 {
return nil, ErrKeyNotFound
}
kv := []*KVPair{}
for _, pair := range pairs {
if pair.Key == prefix {
continue
}
kv = append(kv, &KVPair{pair.Key, pair.Value, pair.ModifyIndex})
}
return kv, nil
}
// DeleteTree deletes a range of keys based on prefix
func (s *Consul) DeleteTree(prefix string) error {
_, err := s.client.KV().DeleteTree(s.normalize(prefix), nil)
return err
}
// Watch changes on a key.
// Returns a channel that will receive changes or an error.
// Upon creating a watch, the current value will be sent to the channel.
// Providing a non-nil stopCh can be used to stop watching.
func (s *Consul) Watch(key string, stopCh <-chan struct{}) (<-chan *KVPair, error) {
key = s.normalize(key)
kv := s.client.KV()
watchCh := make(chan *KVPair)
go func() {
defer close(watchCh)
// Use a wait time in order to check if we should quit from time to
// time.
opts := &api.QueryOptions{WaitTime: DefaultWatchWaitTime}
for {
// Check if we should quit
select {
case <-stopCh:
return
default:
}
pair, meta, err := kv.Get(key, opts)
if err != nil {
log.Errorf("consul: %v", err)
return
}
// If LastIndex didn't change then it means `Get` returned because
// of the WaitTime and the key didn't change.
if opts.WaitIndex == meta.LastIndex {
continue
}
opts.WaitIndex = meta.LastIndex
// FIXME: What happens when a key is deleted?
if pair != nil {
watchCh <- &KVPair{pair.Key, pair.Value, pair.ModifyIndex}
}
}
}()
return watchCh, nil
}
// WatchTree watches changes on a "directory"
// Returns a channel that will receive changes or an error.
// Upon creating a watch, the current value will be sent to the channel.
// Providing a non-nil stopCh can be used to stop watching.
func (s *Consul) WatchTree(prefix string, stopCh <-chan struct{}) (<-chan []*KVPair, error) {
prefix = s.normalize(prefix)
kv := s.client.KV()
watchCh := make(chan []*KVPair)
go func() {
defer close(watchCh)
// Use a wait time in order to check if we should quit from time to
// time.
opts := &api.QueryOptions{WaitTime: DefaultWatchWaitTime}
for {
// Check if we should quit
select {
case <-stopCh:
return
default:
}
pairs, meta, err := kv.List(prefix, opts)
if err != nil {
log.Errorf("consul: %v", err)
return
}
// If LastIndex didn't change then it means `Get` returned because
// of the WaitTime and the key didn't change.
if opts.WaitIndex == meta.LastIndex {
continue
}
opts.WaitIndex = meta.LastIndex
kv := []*KVPair{}
for _, pair := range pairs {
if pair.Key == prefix {
continue
}
kv = append(kv, &KVPair{pair.Key, pair.Value, pair.ModifyIndex})
}
watchCh <- kv
}
}()
return watchCh, nil
}
// NewLock returns a handle to a lock struct which can be used to acquire and
// release the mutex.
func (s *Consul) NewLock(key string, options *LockOptions) (Locker, error) {
consulOpts := &api.LockOptions{
Key: s.normalize(key),
}
if options != nil {
consulOpts.Value = options.Value
}
l, err := s.client.LockOpts(consulOpts)
if err != nil {
return nil, err
}
return &consulLock{lock: l}, nil
}
// Lock attempts to acquire the lock and blocks while doing so.
// Returns a channel that is closed if our lock is lost or an error.
func (l *consulLock) Lock() (<-chan struct{}, error) {
return l.lock.Lock(nil)
}
// Unlock released the lock. It is an error to call this
// if the lock is not currently held.
func (l *consulLock) Unlock() error {
return l.lock.Unlock()
}
// AtomicPut put a value at "key" if the key has not been
// modified in the meantime, throws an error if this is the case
func (s *Consul) AtomicPut(key string, value []byte, previous *KVPair, options *WriteOptions) (bool, *KVPair, error) {
if previous == nil {
return false, nil, ErrPreviousNotSpecified
}
p := &api.KVPair{Key: s.normalize(key), Value: value, ModifyIndex: previous.LastIndex}
if work, _, err := s.client.KV().CAS(p, nil); err != nil {
return false, nil, err
} else if !work {
return false, nil, ErrKeyModified
}
pair, err := s.Get(key)
if err != nil {
return false, nil, err
}
return true, pair, nil
}
// AtomicDelete deletes a value at "key" if the key has not
// been modified in the meantime, throws an error if this is the case
func (s *Consul) AtomicDelete(key string, previous *KVPair) (bool, error) {
if previous == nil {
return false, ErrPreviousNotSpecified
}
p := &api.KVPair{Key: s.normalize(key), ModifyIndex: previous.LastIndex}
if work, _, err := s.client.KV().DeleteCAS(p, nil); err != nil {
return false, err
} else if !work {
return false, ErrKeyModified
}
return true, nil
}
// Close closes the client connection
func (s *Consul) Close() {
return
}