implement pserver RPC part, and simple parameter partition.

doc/design/cluster_train/pserver_client.md

@@ -136,6 +136,9 @@ int paddle_send_grads(paddle_pserver_client* client, const paddle_gradient* grad
 /**
  * @brief paddle_get_params gets parameters from parameter servers.
  *
+ * paddle_get_params will block until parameters are initialized on
+ * the parameter servers.
+ *
  * @param names the array of names of the parameters to get.
  * @param dst the destination array of parameters to save to.
  * @param len the length of the names array and the paddle_parameter

go/pserver/cclient/cclient.go

@@ -39,6 +39,7 @@ import "C"
 
 import (
 	"log"
+	"strings"
 	"sync"
 	"unsafe"
 
@@ -86,29 +87,46 @@ func cArrayToSlice(p unsafe.Pointer, len int) []byte {
 	return (*[1 << 30]byte)(p)[:len:len]
 }
 
+type selector bool
+
+func (s selector) Select() bool {
+	return bool(s)
+}
+
+type lister []pserver.Server
+
+func (l lister) List() []pserver.Server {
+	return l
+}
+
 //export paddle_new_pserver_client
-func paddle_new_pserver_client(addr *C.char) C.client {
-	c := pserver.NewClient(C.GoString(addr))
+func paddle_new_pserver_client(addrs *C.char, selected bool) C.client {
+	a := C.GoString(addrs)
+	as := strings.Split(a, ",")
+	servers := make([]pserver.Server, len(as))
+	for i := range as {
+		servers[i].Index = i
+		servers[i].Addr = as[i]
+	}
+	c := pserver.NewClient(lister(servers), len(as), selector(selected))
 	return add(c)
 }
 
+//export paddle_new_etcd_pserver_client
+func paddle_new_etcd_pserver_client(etcd_addr *C.char) C.client {
+	// TODO(helin): fault tolerant pserver client using etcd.
+	panic("not implemented.")
+}
+
 //export paddle_pserver_client_release
 func paddle_pserver_client_release(client C.client) {
-	c := remove(client)
-	c.Cleanup()
+	remove(client)
 }
 
 //export paddle_begin_init_params
-func paddle_begin_init_params(client C.client, pserver_config unsafe.Pointer, config_len C.int) C.int {
+func paddle_begin_init_params(client C.client) C.int {
 	c := get(client)
-	b := cArrayToSlice(pserver_config, int(config_len))
-	selected, err := c.BeginInitParams(b)
-	if err != nil {
-		log.Println(err)
-		return -1
-	}
-
-	if selected {
+	if selected := c.BeginInitParams(); selected {
 		return 1
 	}
 	return 0
@@ -230,7 +248,7 @@ func paddle_get_params(client C.client, names **C.char, dst **C.paddle_parameter
 func paddle_save_model(client C.client, path *C.char) C.int {
 	p := C.GoString(path)
 	c := get(client)
-	err := c.SaveModel(p)
+	err := c.Save(p)
 	if err != nil {
 		log.Println(err)
 		return -1

go/pserver/client.go

 package pserver
 
+import (
+	"hash/fnv"
+	"log"
+	"sort"
+	"time"
+
+	"github.com/PaddlePaddle/Paddle/paddle/go/pserver/internal/connection"
+)
+
+// TODO(helin): add RPC call retry logic
+
+// Selector selects if the client should initialize parameter servers.
+type Selector interface {
+	Select() bool
+}
+
+// Server is the identification of a parameter Server.
+type Server struct {
+	Index int
+	Addr  string
+}
+
+// Lister lists currently available parameter servers.
+type Lister interface {
+	List() []Server
+}
+
 // Client is the client to parameter servers.
 type Client struct {
+	sel      Selector
+	pservers []*connection.Conn
 }
 
 // NewClient creates a new client.
-func NewClient(addr string) *Client {
-	return &Client{}
+func NewClient(l Lister, pserverNum int, sel Selector) *Client {
+	c := &Client{sel: sel}
+	c.pservers = make([]*connection.Conn, pserverNum)
+	for i := 0; i < pserverNum; i++ {
+		c.pservers[i] = connection.New()
+	}
+	go c.monitorPservers(l, pserverNum)
+	return c
+}
+
+// monitorPservers monitors pserver addresses, and updates connection
+// when the address changes.
+func (c *Client) monitorPservers(l Lister, pserverNum int) {
+	knownServers := make([]Server, pserverNum)
+	ticker := time.NewTicker(10 * time.Second)
+	monitor := func() {
+		curServers := make([]Server, pserverNum)
+		list := l.List()
+		for _, l := range list {
+			curServers[l.Index] = l
+		}
+
+		for i := range knownServers {
+			if knownServers[i].Addr != curServers[i].Addr {
+				err := c.pservers[i].Connect(curServers[i].Addr)
+				if err != nil {
+					log.Println(err)
+
+					// connect to addr failed, set
+					// to last known addr in order
+					// to retry next time.
+					curServers[i].Addr = knownServers[i].Addr
+				}
+			}
+		}
+
+		knownServers = curServers
+	}
+
+	monitor()
+	for _ = range ticker.C {
+		monitor()
+	}
 }
 
 // BeginInitParams begins to initialize parameters on parameter
@@ -17,38 +87,146 @@ func NewClient(addr string) *Client {
 // servers. Other trainers will be blocked until the initialization is
 // done, and they need to get the initialized parameters from
 // parameter servers using GetParams.
-func (c *Client) BeginInitParams(pserverConfigProto []byte) (selected bool, err error) {
-	return true, nil
+func (c *Client) BeginInitParams() bool {
+	return c.sel.Select()
 }
 
 // InitParam initializes the parameter on parameter servers.
 func (c *Client) InitParam(paramWithConfigs ParameterWithConfig) error {
-	return nil
+	var dummy int
+	return c.pservers[c.partition(paramWithConfigs.Param.Name)].Call("Service.InitParam", paramWithConfigs, &dummy)
 }
 
 // FinishInitParams tells parameter servers client has sent all
 // parameters to parameter servers as initialization.
 func (c *Client) FinishInitParams() error {
+	for _, p := range c.pservers {
+		var dummy int
+		err := p.Call("Service.FinishInitParams", dummy, &dummy)
+		if err != nil {
+			return err
+		}
+	}
 	return nil
 }
 
 // SendGrads sends gradients to parameter servers for updating
 // parameters.
 func (c *Client) SendGrads(grads []Gradient) error {
+	errCh := make(chan error, len(grads))
+	for _, g := range grads {
+		go func(g Gradient) {
+			var dummy int
+			err := c.pservers[c.partition(g.Name)].Call("Service.SendGrad", g, &dummy)
+			errCh <- err
+		}(g)
+	}
+
+	recv := 0
+	for err := range errCh {
+		if err != nil {
+			return err
+		}
+
+		recv++
+		if recv == len(grads) {
+			break
+		}
+	}
 	return nil
 }
 
+type result struct {
+	idx int
+	p   Parameter
+	err error
+}
+
+type results []result
+
+func (r results) Len() int {
+	return len(r)
+}
+
+func (r results) Less(i int, j int) bool {
+	return r[i].idx < r[j].idx
+}
+
+func (r results) Swap(i int, j int) {
+	r[i], r[j] = r[j], r[i]
+}
+
 // GetParams gets parameters from parameter servers.
 func (c *Client) GetParams(names []string) ([]Parameter, error) {
-	return nil, nil
+	rCh := make(chan result, len(names))
+
+	for idx, name := range names {
+		go func(name string, idx int) {
+			var parameter Parameter
+			err := c.pservers[c.partition(name)].Call("Service.GetParam", name, &parameter)
+			rCh <- result{idx: idx, p: parameter, err: err}
+		}(name, idx)
+	}
+
+	var rs results
+	recv := 0
+	for r := range rCh {
+		if r.err != nil {
+			return nil, r.err
+		}
+		rs = append(rs, r)
+
+		recv++
+		if recv == len(names) {
+			break
+		}
+	}
+	sort.Sort(rs)
+
+	ps := make([]Parameter, len(rs))
+	for i := range rs {
+		ps[i] = rs[i].p
+	}
+
+	return ps, nil
 }
 
-// SaveModel indicates parameters to save the parameter to the given
-// path.
-func (c *Client) SaveModel(path string) error {
+// Save indicates parameters to save the parameter to the given path.
+func (c *Client) Save(path string) error {
+	errCh := make(chan error, len(c.pservers))
+
+	for _, p := range c.pservers {
+		var dummy int
+		err := p.Call("Service.Save", path, &dummy)
+		errCh <- err
+	}
+
+	recv := 0
+	for err := range errCh {
+		if err != nil {
+			return err
+		}
+
+		recv++
+		if recv == len(c.pservers) {
+			break
+		}
+	}
+
+	// TODO(helin): there will be many files under path, need to
+	// merge them into a single file.
 	return nil
 }
 
-// Cleanup cleans up the client states.
-func (c *Client) Cleanup() {
+func strHash(s string) uint32 {
+	h := fnv.New32a()
+	h.Write([]byte(s))
+	return h.Sum32()
+}
+
+// TODO(helin): now partition only select which parameter server to
+// send the entire parameter. We need to partition a parameter into
+// small blocks and send to different parameter servers.
+func (c *Client) partition(key string) int {
+	return int(strHash(key) % uint32(len(c.pservers)))
 }

go/pserver/optimizer.go

@@ -29,11 +29,11 @@ func newOptimizer(t optimizerType, learning_rate float64) *optimizer {
 
 func (o *optimizer) UpdateParameter(p Parameter, g Gradient) error {
 	if len(p.Content) != len(g.Content) {
-		return fmt.Errorf("parameter and gradient length not match, parameter: %d, gradient: %d", len(p.Content), len(g.Content))
+		return fmt.Errorf("Name: %s, parameter and gradient length not match, parameter: %d, gradient: %d", p.Name, len(p.Content), len(g.Content))
 	}
 
 	if p.ElementType != g.ElementType {
-		return fmt.Errorf("parameter and gradient element type not match, parameter: %v, gradient: %v", p.ElementType, g.ElementType)
+		return fmt.Errorf("Name: %s, parameter and gradient element type not match, parameter: %v, gradient: %v", p.Name, p.ElementType, g.ElementType)
 	}
 
 	r := C.paddle_update_parameter(o.opt, unsafe.Pointer(&p.Content[0]), C.paddle_element_type(p.ElementType), unsafe.Pointer(&g.Content[0]), C.int(len(g.Content)))

go/pserver/service.go

@@ -49,33 +49,12 @@ type Service struct {
 
 // NewService creates a new service.
 func NewService() *Service {
-	s := &Service{}
+	s := &Service{opt: newOptimizer(sgd, 0.01)}
 	s.paramMap = make(map[string]Parameter)
 	s.initialized = make(chan struct{})
 	return s
 }
 
-// BeginInitParams tells the parameter server that the parameter
-// initialization has begun.
-func (s *Service) BeginInitParams(config []byte, dummy *int) error {
-	select {
-	case <-s.initialized:
-		return ErrAlreadyInitialized
-	default:
-	}
-
-	s.mu.Lock()
-	defer s.mu.Unlock()
-
-	if s.opt != nil {
-		s.opt.Cleanup()
-	}
-
-	// TODO(helin): parse learning rate from config
-	s.opt = newOptimizer(sgd, 0.01)
-	return nil
-}
-
 // InitParam initializes a parameter.
 func (s *Service) InitParam(paramWithConfigs ParameterWithConfig, dummy *int) error {
 	select {
@@ -109,75 +88,45 @@ func (s *Service) FinishInitParams(dummy0 int, dummy1 *int) error {
 	return nil
 }
 
-// SendGrads sends gradients to parameter servers for parameter
+// SendGrad sends gradient to parameter servers for parameter
 // optimization.
-func (s *Service) SendGrads(grads []Gradient, dummy *int) error {
+func (s *Service) SendGrad(g Gradient, dummy *int) error {
 	select {
 	case <-s.initialized:
 	default:
 		return ErrUninitialized
 	}
 
-	count := len(grads)
-	if count == 0 {
-		return nil
-	}
-
 	s.mu.Lock()
 	defer s.mu.Unlock()
 
-	for _, g := range grads {
-		if _, ok := s.paramMap[g.Name]; !ok {
-			return fmt.Errorf("parameter: %s does not exist", g.Name)
-		}
-	}
-
-	errCh := make(chan error, count)
-	for _, g := range grads {
-		go func(p Parameter, g Gradient) {
-			err := s.opt.UpdateParameter(p, g)
-			errCh <- err
-		}(s.paramMap[g.Name], g)
+	p, ok := s.paramMap[g.Name]
+	if !ok {
+		return fmt.Errorf("parameter: %s does not exist", g.Name)
 	}
 
-	recv := 0
-	for err := range errCh {
-		if err != nil {
-			return err
-		}
-
-		recv++
-		if recv == count {
-			break
-		}
-	}
-	return nil
+	return s.opt.UpdateParameter(p, g)
 }
 
-// GetParams gets parameters from the parameter server.
-func (s *Service) GetParams(names []string, parameters *[]Parameter) error {
+// GetParam gets parameters from the parameter server.
+func (s *Service) GetParam(name string, parameter *Parameter) error {
 	<-s.initialized
 	s.mu.Lock()
 	defer s.mu.Unlock()
 
-	for _, n := range names {
-		if _, ok := s.paramMap[n]; !ok {
-			return fmt.Errorf("parameter: %s does not exist", n)
-		}
-	}
-
-	*parameters = make([]Parameter, len(names))
-	for i, n := range names {
-		// The parameter content (a byte slice) may change
-		// during RPC serialization due to write from other
-		// goroutine, we allow it since mini-batch based deep
-		// learning optimization methods are stochastic in
-		// nature. This race condition is allowed deliberately
-		// to save the program from making a copy of the
-		// paramter content.
-		(*parameters)[i] = s.paramMap[n]
+	p, ok := s.paramMap[name]
+	if !ok {
+		return fmt.Errorf("parameter: %s does not exist", name)
 	}
 
+	// The parameter content (a byte slice) may change
+	// during RPC serialization due to write from other
+	// goroutine, we allow it since mini-batch based deep
+	// learning optimization methods are stochastic in
+	// nature. This race condition is allowed deliberately
+	// to save the program from making a copy of the
+	// paramter content.
+	*parameter = p
 	return nil
 }
 

go/pserver/service_test.go

@@ -4,23 +4,19 @@ import (
 	"reflect"
 	"sync"
 	"testing"
+	"time"
 
 	"github.com/PaddlePaddle/Paddle/go/pserver"
 )
 
 func TestFull(t *testing.T) {
 	s := pserver.NewService()
-	var dummy int
-	err := s.BeginInitParams(nil, &dummy)
-	if err != nil {
-		t.FailNow()
-	}
-
 	var p pserver.Parameter
 	p.Name = "param_a"
 	p.Content = []byte{1, 0, 0, 0, 2, 0, 0, 0, 3, 0, 0, 0}
 	p.ElementType = pserver.Int32
-	err = s.InitParam(pserver.ParameterWithConfig{p, nil}, &dummy)
+	var dummy int
+	err := s.InitParam(pserver.ParameterWithConfig{p, nil}, &dummy)
 	if err != nil {
 		t.FailNow()
 	}
@@ -39,40 +35,39 @@ func TestFull(t *testing.T) {
 		t.FailNow()
 	}
 
-	var params []pserver.Parameter
-	err = s.GetParams([]string{"param_b", "param_a"}, &params)
+	var param pserver.Parameter
+	err = s.GetParam("param_b", &param)
 	if err != nil {
 		t.FailNow()
 	}
 
-	if len(params) != 2 || !reflect.DeepEqual(params[0], p1) || !reflect.DeepEqual(params[0], p1) {
+	if !reflect.DeepEqual(param, p1) {
 		t.FailNow()
 	}
 
-	grads := []pserver.Gradient{pserver.Gradient(p1), pserver.Gradient(p)}
-	err = s.SendGrads(grads, &dummy)
+	g1, g2 := pserver.Gradient(p1), pserver.Gradient(p)
+	err = s.SendGrad(g1, &dummy)
 	if err != nil {
 		t.FailNow()
 	}
+	err = s.SendGrad(g2, &dummy)
 
-	var params1 []pserver.Parameter
-	err = s.GetParams([]string{"param_b", "param_a"}, &params1)
 	if err != nil {
 		t.FailNow()
 	}
 
-	if len(params) != 2 {
+	var param1 pserver.Parameter
+	err = s.GetParam("param_a", &param1)
+	if err != nil {
 		t.FailNow()
 	}
 
 	// don't compare content, since it's already changed by
 	// gradient update.
-	params1[0].Content = nil
-	params1[0].Content = nil
+	param1.Content = nil
 	p.Content = nil
-	p1.Content = nil
 
-	if !reflect.DeepEqual(params1[0], p1) || !reflect.DeepEqual(params1[0], p1) {
+	if !reflect.DeepEqual(param1, p) {
 		t.FailNow()
 	}
 }
@@ -80,19 +75,7 @@ func TestFull(t *testing.T) {
 func TestMultipleInit(t *testing.T) {
 	s := pserver.NewService()
 	var dummy int
-	err := s.BeginInitParams(nil, &dummy)
-	if err != nil {
-		t.FailNow()
-	}
-
-	// this is fine, it's possible for client to call init
-	// multiple times.
-	err = s.BeginInitParams(nil, &dummy)
-	if err != nil {
-		t.FailNow()
-	}
-
-	err = s.FinishInitParams(0, &dummy)
+	err := s.FinishInitParams(0, &dummy)
 	if err != nil {
 		t.FailNow()
 	}
@@ -101,17 +84,12 @@ func TestMultipleInit(t *testing.T) {
 	if err != pserver.ErrAlreadyInitialized {
 		t.FailNow()
 	}
-
-	err = s.BeginInitParams(nil, &dummy)
-	if err != pserver.ErrAlreadyInitialized {
-		t.FailNow()
-	}
 }
 
 func TestUninitialized(t *testing.T) {
 	s := pserver.NewService()
 	var dummy int
-	err := s.SendGrads(nil, &dummy)
+	err := s.SendGrad(pserver.Gradient{}, &dummy)
 	if err != pserver.ErrUninitialized {
 		t.FailNow()
 	}
@@ -123,8 +101,8 @@ func TestBlockUntilInitialized(t *testing.T) {
 	var wg sync.WaitGroup
 	wg.Add(1)
 	go func() {
-		var params []pserver.Parameter
-		err := s.GetParams(nil, &params)
+		var param pserver.Parameter
+		err := s.GetParam("param_a", &param)
 		if err != nil {
 			t.FailNow()
 		}
@@ -143,11 +121,7 @@ func TestBlockUntilInitialized(t *testing.T) {
 		ch <- struct{}{}
 	}()
 
-	var dummy int
-	err := s.BeginInitParams(nil, &dummy)
-	if err != nil {
-		t.FailNow()
-	}
+	time.Sleep(50 * time.Millisecond)
 
 	select {
 	case <-ch:
@@ -156,6 +130,16 @@ func TestBlockUntilInitialized(t *testing.T) {
 	default:
 	}
 
+	var p pserver.Parameter
+	p.Name = "param_a"
+	p.Content = []byte{1, 0, 0, 0, 2, 0, 0, 0, 3, 0, 0, 0}
+	p.ElementType = pserver.Int32
+	var dummy int
+	err := s.InitParam(pserver.ParameterWithConfig{p, nil}, &dummy)
+	if err != nil {
+		t.FailNow()
+	}
+
 	err = s.FinishInitParams(0, &dummy)
 	if err != nil {
 		t.FailNow()

paddle/go/pserver/client_test.go

+package pserver_test
+
+import (
+	"net"
+	"net/http"
+	"net/rpc"
+	"strconv"
+	"strings"
+	"testing"
+
+	"github.com/PaddlePaddle/Paddle/paddle/go/pserver"
+)
+
+const numPserver = 10
+
+var port [numPserver]int
+
+func init() {
+	for i := 0; i < numPserver; i++ {
+		l, err := net.Listen("tcp", ":0")
+		if err != nil {
+			panic(err)
+		}
+
+		ss := strings.Split(l.Addr().String(), ":")
+		p, err := strconv.Atoi(ss[len(ss)-1])
+		if err != nil {
+			panic(err)
+		}
+		port[i] = p
+
+		go func(l net.Listener) {
+			s := pserver.NewService()
+			server := rpc.NewServer()
+			err := server.Register(s)
+			if err != nil {
+				panic(err)
+			}
+
+			mux := http.NewServeMux()
+			mux.Handle(rpc.DefaultRPCPath, server)
+			err = http.Serve(l, mux)
+			if err != nil {
+				panic(err)
+			}
+		}(l)
+	}
+}
+
+type selector bool
+
+func (s selector) Select() bool {
+	return bool(s)
+}
+
+type lister []pserver.Server
+
+func (l lister) List() []pserver.Server {
+	return l
+}
+
+func TestClientFull(t *testing.T) {
+	servers := make([]pserver.Server, numPserver)
+	for i := 0; i < numPserver; i++ {
+		servers[i] = pserver.Server{Index: i, Addr: ":" + strconv.Itoa(port[i])}
+	}
+	c := pserver.NewClient(lister(servers), len(servers), selector(true))
+	selected := c.BeginInitParams()
+	if !selected {
+		t.Fatal("should be selected.")
+	}
+
+	const numParameter = 100
+	for i := 0; i < numParameter; i++ {
+		var p pserver.Parameter
+		p.Name = "p_" + strconv.Itoa(i)
+		p.ElementType = pserver.Float32
+		p.Content = make([]byte, (i+1)*100)
+		err := c.InitParam(pserver.ParameterWithConfig{Param: p})
+		if err != nil {
+			t.Fatal(err)
+		}
+	}
+
+	err := c.FinishInitParams()
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	var grads []pserver.Gradient
+	for i := 0; i < numParameter/2; i++ {
+		var g pserver.Gradient
+		g.Name = "p_" + strconv.Itoa(i)
+		g.ElementType = pserver.Float32
+		g.Content = make([]byte, (i+1)*100)
+		grads = append(grads, g)
+	}
+
+	err = c.SendGrads(grads)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	names := make([]string, numParameter)
+	for i := 0; i < numParameter; i++ {
+		names[i] = "p_" + strconv.Itoa(i)
+	}
+
+	params, err := c.GetParams(names)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if len(names) != len(params) {
+		t.Fatalf("parameter size not match, need: %d, have: %d", len(names), len(params))
+	}
+
+	for i := range params {
+		if names[i] != params[i].Name {
+			t.Fatalf("order of returned parameter does not required: parameter name: %s, required name: %s", names[i], params[i])
+		}
+	}
+}

paddle/go/pserver/internal/connection/conn.go

+package connection
+
+import (
+	"errors"
+	"net/rpc"
+	"sync"
+)
+
+// TODO(helin): add TCP re-connect logic
+
+// Conn is a connection to a parameter server
+type Conn struct {
+	mu       sync.Mutex
+	client   *rpc.Client
+	waitConn chan struct{}
+}
+
+// New creates a new connection.
+func New() *Conn {
+	c := &Conn{}
+	return c
+}
+
+// Connect connects the connection to a address.
+func (c *Conn) Connect(addr string) error {
+	c.mu.Lock()
+	if c.client != nil {
+		err := c.client.Close()
+		if err != nil {
+			c.mu.Unlock()
+			return err
+		}
+
+		c.client = nil
+	}
+	c.mu.Unlock()
+
+	client, err := rpc.DialHTTP("tcp", addr)
+	if err != nil {
+		return err
+	}
+
+	c.mu.Lock()
+	defer c.mu.Unlock()
+
+	if c.client == nil {
+		c.client = client
+		if c.waitConn != nil {
+			close(c.waitConn)
+			c.waitConn = nil
+		}
+	} else {
+		return errors.New("client already set from a concurrent goroutine")
+	}
+
+	return nil
+}
+
+// Call make a RPC call.
+//
+// Call will be blocked until the connection to remote RPC service
+// being established.
+func (c *Conn) Call(serviceMethod string, args interface{}, reply interface{}) error {
+	c.mu.Lock()
+	client := c.client
+	var waitCh chan struct{}
+	if client == nil {
+		if c.waitConn != nil {
+			waitCh = c.waitConn
+		} else {
+			waitCh = make(chan struct{})
+			c.waitConn = waitCh
+		}
+	}
+	c.mu.Unlock()
+
+	if waitCh != nil {
+		// wait until new connection being established
+		<-waitCh
+		return c.Call(serviceMethod, args, reply)
+	}
+
+	return client.Call(serviceMethod, args, reply)
+}

paddle/go/pserver/partitioner.go

+package pserver
+
+type partitioner struct {
+	shardNum int
+}
+
+// partitioner partitions the parameters into shards.
+func newPartitioner(shardNum int) *partitioner {
+	return &partitioner{shardNum: shardNum}
+}