traefik/cluster/datastore.go
Ed Robinson ac20ddfc6c
Fix golint
recent additions to golint mean that a number of files cause the
build to start failing if they are edited (we only run against changed
files)

This fixes all the errors in the repo so things don't unexpectedly start
failing for people making PRs
2016-11-16 11:52:15 +01:00

253 lines
5.6 KiB
Go

package cluster
import (
"encoding/json"
"fmt"
"github.com/cenk/backoff"
"github.com/containous/staert"
"github.com/containous/traefik/job"
"github.com/containous/traefik/log"
"github.com/docker/libkv/store"
"github.com/satori/go.uuid"
"golang.org/x/net/context"
"sync"
"time"
)
// Metadata stores Object plus metadata
type Metadata struct {
object Object
Object []byte
Lock string
}
// NewMetadata returns new Metadata
func NewMetadata(object Object) *Metadata {
return &Metadata{object: object}
}
// Marshall marshalls object
func (m *Metadata) Marshall() error {
var err error
m.Object, err = json.Marshal(m.object)
return err
}
func (m *Metadata) unmarshall() error {
if len(m.Object) == 0 {
return nil
}
return json.Unmarshal(m.Object, m.object)
}
// Listener is called when Object has been changed in KV store
type Listener func(Object) error
var _ Store = (*Datastore)(nil)
// Datastore holds a struct synced in a KV store
type Datastore struct {
kv staert.KvSource
ctx context.Context
localLock *sync.RWMutex
meta *Metadata
lockKey string
listener Listener
}
// NewDataStore creates a Datastore
func NewDataStore(ctx context.Context, kvSource staert.KvSource, object Object, listener Listener) (*Datastore, error) {
datastore := Datastore{
kv: kvSource,
ctx: ctx,
meta: &Metadata{object: object},
lockKey: kvSource.Prefix + "/lock",
localLock: &sync.RWMutex{},
listener: listener,
}
err := datastore.watchChanges()
if err != nil {
return nil, err
}
return &datastore, nil
}
func (d *Datastore) watchChanges() error {
stopCh := make(chan struct{})
kvCh, err := d.kv.Watch(d.lockKey, stopCh)
if err != nil {
return err
}
go func() {
ctx, cancel := context.WithCancel(d.ctx)
operation := func() error {
for {
select {
case <-ctx.Done():
stopCh <- struct{}{}
return nil
case _, ok := <-kvCh:
if !ok {
cancel()
return err
}
err = d.reload()
if err != nil {
return err
}
// log.Debugf("Datastore object change received: %+v", d.meta)
if d.listener != nil {
err := d.listener(d.meta.object)
if err != nil {
log.Errorf("Error calling datastore listener: %s", err)
}
}
}
}
}
notify := func(err error, time time.Duration) {
log.Errorf("Error in watch datastore: %+v, retrying in %s", err, time)
}
err := backoff.RetryNotify(operation, job.NewBackOff(backoff.NewExponentialBackOff()), notify)
if err != nil {
log.Errorf("Error in watch datastore: %v", err)
}
}()
return nil
}
func (d *Datastore) reload() error {
log.Debugf("Datastore reload")
d.localLock.Lock()
err := d.kv.LoadConfig(d.meta)
if err != nil {
d.localLock.Unlock()
return err
}
err = d.meta.unmarshall()
if err != nil {
d.localLock.Unlock()
return err
}
d.localLock.Unlock()
return nil
}
// Begin creates a transaction with the KV store.
func (d *Datastore) Begin() (Transaction, Object, error) {
id := uuid.NewV4().String()
log.Debugf("Transaction %s begins", id)
remoteLock, err := d.kv.NewLock(d.lockKey, &store.LockOptions{TTL: 20 * time.Second, Value: []byte(id)})
if err != nil {
return nil, nil, err
}
stopCh := make(chan struct{})
ctx, cancel := context.WithCancel(d.ctx)
var errLock error
go func() {
_, errLock = remoteLock.Lock(stopCh)
cancel()
}()
select {
case <-ctx.Done():
if errLock != nil {
return nil, nil, errLock
}
case <-d.ctx.Done():
stopCh <- struct{}{}
return nil, nil, d.ctx.Err()
}
// we got the lock! Now make sure we are synced with KV store
operation := func() error {
meta := d.get()
if meta.Lock != id {
return fmt.Errorf("Object lock value: expected %s, got %s", id, meta.Lock)
}
return nil
}
notify := func(err error, time time.Duration) {
log.Errorf("Datastore sync error: %v, retrying in %s", err, time)
err = d.reload()
if err != nil {
log.Errorf("Error reloading: %+v", err)
}
}
ebo := backoff.NewExponentialBackOff()
ebo.MaxElapsedTime = 60 * time.Second
err = backoff.RetryNotify(operation, ebo, notify)
if err != nil {
return nil, nil, fmt.Errorf("Datastore cannot sync: %v", err)
}
// we synced with KV store, we can now return Setter
return &datastoreTransaction{
Datastore: d,
remoteLock: remoteLock,
id: id,
}, d.meta.object, nil
}
func (d *Datastore) get() *Metadata {
d.localLock.RLock()
defer d.localLock.RUnlock()
return d.meta
}
// Load load atomically a struct from the KV store
func (d *Datastore) Load() (Object, error) {
d.localLock.Lock()
defer d.localLock.Unlock()
err := d.kv.LoadConfig(d.meta)
if err != nil {
return nil, err
}
err = d.meta.unmarshall()
if err != nil {
return nil, err
}
return d.meta.object, nil
}
// Get atomically a struct from the KV store
func (d *Datastore) Get() Object {
d.localLock.RLock()
defer d.localLock.RUnlock()
return d.meta.object
}
var _ Transaction = (*datastoreTransaction)(nil)
type datastoreTransaction struct {
*Datastore
remoteLock store.Locker
dirty bool
id string
}
// Commit allows to set an object in the KV store
func (s *datastoreTransaction) Commit(object Object) error {
s.localLock.Lock()
defer s.localLock.Unlock()
if s.dirty {
return fmt.Errorf("transaction already used, please begin a new one")
}
s.Datastore.meta.object = object
err := s.Datastore.meta.Marshall()
if err != nil {
return err
}
err = s.kv.StoreConfig(s.Datastore.meta)
if err != nil {
return err
}
err = s.remoteLock.Unlock()
if err != nil {
return err
}
s.dirty = true
log.Debugf("Transaction commited %s", s.id)
return nil
}