Helin Wang
8 years ago
parent
f277726c72
commit
fd8937556f
@ -0,0 +1,133 @@
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package master
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import (
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"context"
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"sync"
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"github.com/coreos/etcd/clientv3"
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"github.com/coreos/etcd/clientv3/concurrency"
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log "github.com/sirupsen/logrus"
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)
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const (
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// DefaultLockPath is the default etcd master lock path.
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DefaultLockPath = "/master/lock"
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// DefaultStatePath is the default etcd key for master state.
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DefaultStatePath = "/master/state"
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)
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// EtcdStore is the Store implementation backed by etcd.
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type EtcdStore struct {
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lockPath string
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statePath string
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ttlSec int
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client *clientv3.Client
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mu sync.Mutex
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lock *concurrency.Mutex
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}
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// NewEtcdStore creates a new EtcdStore.
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func NewEtcdStore(endpoints []string, lockPath, statePath string, ttlSec int) (*EtcdStore, error) {
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cli, err := clientv3.New(clientv3.Config{
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Endpoints: endpoints,
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DialTimeout: dialTimeout,
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})
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if err != nil {
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return nil, err
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}
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sess, err := concurrency.NewSession(cli, concurrency.WithTTL(ttlSec))
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if err != nil {
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return nil, err
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}
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lock := concurrency.NewMutex(sess, lockPath)
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// It's fine for the lock to get stuck, in this case we have
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// multiple master servers running (only configured to have
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// one master running, but split-brain problem may cuase
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// multiple master servers running), and the cluster management
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// software will kill one of them.
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log.Infof("Trying to acquire lock at %s.", lockPath)
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err = lock.Lock(context.TODO())
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if err != nil {
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return nil, err
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}
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log.Infof("Successfully acquired lock at %s.", lockPath)
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e := &EtcdStore{}
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e.client = cli
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e.lock = lock
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e.lockPath = lockPath
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e.statePath = statePath
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e.ttlSec = ttlSec
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return e, nil
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}
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// Save saves the state into the etcd.
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func (e *EtcdStore) Save(state []byte) error {
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e.mu.Lock()
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defer e.mu.Unlock()
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ctx := context.TODO()
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put := clientv3.OpPut(e.statePath, string(state))
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resp, err := e.client.Txn(ctx).If(e.lock.IsOwner()).Then(put).Commit()
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if err != nil {
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return err
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}
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if !resp.Succeeded {
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log.Errorln("No longer owns the lock, trying to lock and save again.")
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sess, err := concurrency.NewSession(e.client, concurrency.WithTTL(e.ttlSec))
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if err != nil {
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return err
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}
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e.lock = concurrency.NewMutex(sess, e.lockPath)
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log.Infof("Try to acquire lock at %s.", e.lockPath)
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err = e.lock.Lock(context.TODO())
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if err != nil {
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return err
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}
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log.Infof("Successfully acquired lock at %s.", e.lockPath)
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return e.Save(state)
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}
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return nil
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}
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// Load loads the state from etcd.
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func (e *EtcdStore) Load() ([]byte, error) {
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e.mu.Lock()
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ctx := context.TODO()
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get := clientv3.OpGet(e.statePath)
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resp, err := e.client.Txn(ctx).If(e.lock.IsOwner()).Then(get).Commit()
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if err != nil {
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return nil, err
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}
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if !resp.Succeeded {
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log.Errorln("No longer owns the lock, trying to lock and load again.")
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sess, err := concurrency.NewSession(e.client)
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if err != nil {
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return nil, err
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}
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e.lock = concurrency.NewMutex(sess, e.lockPath)
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e.lock.Lock(context.TODO())
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e.mu.Unlock()
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return e.Load()
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}
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kvs := resp.Responses[0].GetResponseRange().Kvs
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if len(kvs) == 0 {
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// No state exists
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e.mu.Unlock()
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return nil, nil
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}
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state := kvs[0].Value
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e.mu.Unlock()
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return state, nil
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}
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