gracefully shutdown master, pserver, fix gometalinter errors

go/cmd/master/master.go

@@ -19,6 +19,8 @@ import (
 	"net"
 	"net/http"
 	"net/rpc"
+	"os"
+	"os/signal"
 	"strconv"
 	"strings"
 	"time"
@@ -68,6 +70,20 @@ func main() {
 		store = &master.InMemStore{}
 	}
 
+	shutdown := func() {
+		log.Infoln("shutting down gracefully")
+		err := store.Shutdown()
+		if err != nil {
+			log.Errorln(err)
+		}
+	}
+
+	// Guaranteed to run even panic happens.
+	defer shutdown()
+
+	c := make(chan os.Signal, 1)
+	signal.Notify(c, os.Interrupt)
+
 	s, err := master.NewService(store, *chunkPerTask, *taskTimeoutDur, *taskTimeoutMax)
 	if err != nil {
 		log.Fatal(err)
@@ -84,8 +100,12 @@ func main() {
 		log.Fatal(err)
 	}
 
-	err = http.Serve(l, nil)
-	if err != nil {
-		log.Fatal(err)
-	}
+	go func() {
+		err = http.Serve(l, nil)
+		if err != nil {
+			log.Fatal(err)
+		}
+	}()
+
+	<-c
 }

go/cmd/pserver/pserver.go

@@ -18,6 +18,8 @@ import (
 	"net"
 	"net/http"
 	"net/rpc"
+	"os"
+	"os/signal"
 	"strconv"
 	"time"
 
@@ -33,7 +35,8 @@ func main() {
 	index := flag.Int("index", -1, "index of this pserver, should be larger or equal than 0")
 	etcdEndpoint := flag.String("etcd-endpoint", "http://127.0.0.1:2379",
 		"comma separated endpoint string for pserver to connect to etcd")
-	etcdTimeout := flag.Duration("etcd-timeout", 5*time.Second, "timeout for etcd calls")
+	dialTimeout := flag.Duration("dial-timeout", 5*time.Second, "dial timeout")
+	etcdTTL := flag.Int("etcd-ttl", 5, "etcd time to live in seconds")
 	numPservers := flag.Int("num-pservers", 1, "total pserver count in a training job")
 	checkpointPath := flag.String("checkpoint-path", "/checkpoints/", "save checkpoint path")
 	checkpointInterval := flag.Duration("checkpoint-interval", 600*time.Second, "save checkpoint per interval seconds")
@@ -53,7 +56,7 @@ func main() {
 	if *index >= 0 {
 		idx = *index
 	} else {
-		e = pserver.NewEtcdClient(*etcdEndpoint, *numPservers, *etcdTimeout)
+		e = pserver.NewEtcdClient(*etcdEndpoint, *numPservers, *dialTimeout, *etcdTTL)
 		idx, err = e.Register(*port)
 		candy.Must(err)
 
@@ -67,6 +70,20 @@ func main() {
 		}
 	}
 
+	shutdown := func() {
+		log.Infoln("shutting down gracefully")
+		sErr := e.Shutdown()
+		if sErr != nil {
+			log.Errorln(sErr)
+		}
+	}
+
+	// Guaranteed to run even panic happens.
+	defer shutdown()
+
+	c := make(chan os.Signal, 1)
+	signal.Notify(c, os.Interrupt)
+
 	s, err := pserver.NewService(idx, *checkpointInterval, *checkpointPath, e, cp)
 	candy.Must(err)
 
@@ -77,7 +94,11 @@ func main() {
 	l, err := net.Listen("tcp", ":"+strconv.Itoa(*port))
 	candy.Must(err)
 
-	log.Infof("start pserver at port %d", *port)
-	err = http.Serve(l, nil)
-	candy.Must(err)
+	go func() {
+		log.Infof("start pserver at port %d", *port)
+		err = http.Serve(l, nil)
+		candy.Must(err)
+	}()
+
+	<-c
 }

go/master/etcd_client.go

@@ -39,15 +39,12 @@ type EtcdClient struct {
 	statePath string
 	client    *clientv3.Client
 	lock      *concurrency.Mutex
+	sess      *concurrency.Session
 }
 
 // NewEtcdClient creates a new EtcdClient.
 func NewEtcdClient(endpoints []string, addr string, lockPath, addrPath, statePath string, ttlSec int) (*EtcdClient, error) {
 	log.Debugf("Connecting to etcd at %v", endpoints)
-	// TODO(helin): gracefully shutdown etcd store. Because etcd
-	// store holds a etcd lock, even though the lock will expire
-	// when the lease timeout, we need to implement graceful
-	// shutdown to release the lock.
 	cli, err := clientv3.New(clientv3.Config{
 		Endpoints:   endpoints,
 		DialTimeout: dialTimeout,
@@ -67,12 +64,12 @@ func NewEtcdClient(endpoints []string, addr string, lockPath, addrPath, statePat
 	// one master running, but split-brain problem may cause
 	// multiple master servers running), and the cluster management
 	// software will kill one of them.
-	log.Debugf("Trying to acquire lock at %s.", lockPath)
+	log.Infof("Trying to acquire lock at %s.", lockPath)
 	err = lock.Lock(context.TODO())
 	if err != nil {
 		return nil, err
 	}
-	log.Debugf("Successfully acquired lock at %s.", lockPath)
+	log.Infof("Successfully acquired lock at %s.", lockPath)
 
 	put := clientv3.OpPut(addrPath, addr)
 	resp, err := cli.Txn(context.Background()).If(lock.IsOwner()).Then(put).Commit()
@@ -89,6 +86,7 @@ func NewEtcdClient(endpoints []string, addr string, lockPath, addrPath, statePat
 		statePath: statePath,
 		client:    cli,
 		lock:      lock,
+		sess:      sess,
 	}
 
 	return e, nil
@@ -157,6 +155,21 @@ func (e *EtcdClient) Load() ([]byte, error) {
 	return state, nil
 }
 
+// Shutdown shuts down the etcd client gracefully.
+func (e *EtcdClient) Shutdown() error {
+	err := e.sess.Close()
+	newErr := e.client.Close()
+	if newErr != nil {
+		if err == nil {
+			err = newErr
+		} else {
+			log.Errorln(newErr)
+		}
+	}
+
+	return err
+}
+
 // GetKey gets the value by the specify key.
 func GetKey(c *clientv3.Client, key string, timeout time.Duration) (string, error) {
 	ctx, cancel := context.WithTimeout(context.Background(), timeout)

go/master/inmem_store.go

@@ -40,3 +40,8 @@ func (m *InMemStore) Load() ([]byte, error) {
 
 	return m.buf, nil
 }
+
+// Shutdown shuts down the in mem store.
+func (m *InMemStore) Shutdown() error {
+	return nil
+}

go/master/service.go

@@ -50,6 +50,7 @@ var ErrPassAfter = errors.New("pass number larger than master")
 type Store interface {
 	Save([]byte) error
 	Load() ([]byte, error)
+	Shutdown() error
 }
 
 // Chunk is a chunk of data consisted of several data instances.

go/pserver/client/c/cclient.go

@@ -55,10 +55,10 @@ var curHandle C.paddle_pserver_client
 func add(c *client.Client) C.paddle_pserver_client {
 	mu.Lock()
 	defer mu.Unlock()
-	client := curHandle
+	cli := curHandle
 	curHandle++
-	handleMap[client] = c
-	return client
+	handleMap[cli] = c
+	return cli
 }
 
 func get(client C.paddle_pserver_client) *client.Client {