Stats: Add ChannelConfig & Return error on subscription

app/stats/channel.go

@@ -5,15 +5,33 @@ package stats
 import (
 	"sync"
 	"time"
+
+	"v2ray.com/core/common"
 )
 
 // Channel is an implementation of stats.Channel.
 type Channel struct {
+	channel     chan interface{}
+	subscribers []chan interface{}
+
+	// Synchronization components
 	access sync.RWMutex
 	closed chan struct{}
 
-	channel     chan interface{}
+	// Channel options
-	subscribers []chan interface{}
+	subscriberLimit   int           // Set to 0 as no subscriber limit
+	channelBufferSize int           // Set to 0 as no buffering
+	broadcastTimeout  time.Duration // Set to 0 as non-blocking immediate timeout
+}
+
+// NewChannel creates an instance of Statistics Channel.
+func NewChannel(config *ChannelConfig) *Channel {
+	return &Channel{
+		channel:           make(chan interface{}, config.BufferSize),
+		subscriberLimit:   int(config.SubscriberLimit),
+		channelBufferSize: int(config.BufferSize),
+		broadcastTimeout:  time.Duration(config.BroadcastTimeout+1) * time.Millisecond,
+	}
 }
 
 // Channel returns the underlying go channel.
@@ -31,16 +49,19 @@ func (c *Channel) Subscribers() []chan interface{} {
 }
 
 // Subscribe implements stats.Channel.
-func (c *Channel) Subscribe() chan interface{} {
+func (c *Channel) Subscribe() (chan interface{}, error) {
 	c.access.Lock()
 	defer c.access.Unlock()
-	subscriber := make(chan interface{})
+	if c.subscriberLimit > 0 && len(c.subscribers) >= c.subscriberLimit {
+		return nil, newError("Number of subscribers has reached limit")
+	}
+	subscriber := make(chan interface{}, c.channelBufferSize)
 	c.subscribers = append(c.subscribers, subscriber)
-	return subscriber
+	return subscriber, nil
 }
 
 // Unsubscribe implements stats.Channel.
-func (c *Channel) Unsubscribe(subscriber chan interface{}) {
+func (c *Channel) Unsubscribe(subscriber chan interface{}) error {
 	c.access.Lock()
 	defer c.access.Unlock()
 	for i, s := range c.subscribers {
@@ -50,9 +71,9 @@ func (c *Channel) Unsubscribe(subscriber chan interface{}) {
 			copy(subscribers[:i], c.subscribers[:i])
 			copy(subscribers[i:], c.subscribers[i+1:])
 			c.subscribers = subscribers
-			return
 		}
 	}
+	return nil
 }
 
 // Publish implements stats.Channel.
@@ -85,12 +106,7 @@ func (c *Channel) Running() bool {
 func (c *Channel) Start() error {
 	c.access.Lock()
 	defer c.access.Unlock()
-	if c.Running() {
+	if !c.Running() {
-		return nil
-	}
-	if c.channel == nil { // Initialize publisher channel
-		c.channel = make(chan interface{}, 16)
-	}
 		c.closed = make(chan struct{}) // Reset close signal
 		go func() {
 			for {
@@ -99,20 +115,21 @@ func (c *Channel) Start() error {
 					for _, sub := range c.Subscribers() { // Concurrency-safe subscribers retreivement
 						select {
 						case sub <- message: // Successfully sent message
-					case <-time.After(100 * time.Millisecond):
+						case <-time.After(c.broadcastTimeout): // Remove timeout subscriber
-						c.Unsubscribe(sub) // Remove timeout subscriber
+							common.Must(c.Unsubscribe(sub))
 							close(sub) // Actively close subscriber as notification
 						}
 					}
 				case <-c.closed: // Channel closed
 					for _, sub := range c.Subscribers() { // Remove all subscribers
-					c.Unsubscribe(sub)
+						common.Must(c.Unsubscribe(sub))
 						close(sub)
 					}
 					return
 				}
 			}
 		}()
+	}
 	return nil
 }
 

app/stats/channel_test.go

@@ -1,7 +1,6 @@
 package stats_test
 
 import (
-	"context"
 	"fmt"
 	"testing"
 	"time"
@@ -12,25 +11,30 @@ import (
 )
 
 func TestStatsChannel(t *testing.T) {
-	raw, err := common.CreateObject(context.Background(), &Config{})
+	// At most 2 subscribers could be registered
+	c := NewChannel(&ChannelConfig{SubscriberLimit: 2})
+	source := c.Channel()
+
+	a, err := stats.SubscribeRunnableChannel(c)
+	common.Must(err)
+	if !c.Running() {
+		t.Fatal("unexpected failure in running channel after first subscription")
+	}
+
+	b, err := c.Subscribe()
 	common.Must(err)
 
-	m := raw.(stats.Manager)
+	// Test that third subscriber is forbidden
-	c, err := m.RegisterChannel("test.channel")
+	_, err = c.Subscribe()
-	common.Must(err)
+	if err == nil {
-	common.Must(m.Start())
+		t.Fatal("unexpected successful subscription")
-	defer m.Close()
+	}
-
+	t.Log("expected error: ", err)
-	source := c.(*Channel).Channel()
-	a := c.Subscribe()
-	b := c.Subscribe()
-	defer c.Unsubscribe(a)
-	defer c.Unsubscribe(b)
 
 	stopCh := make(chan struct{})
 	errCh := make(chan string)
 
-	go func() {
+	go func() { // Blocking publish
 		source <- 1
 		source <- 2
 		source <- "3"
@@ -84,22 +88,31 @@ func TestStatsChannel(t *testing.T) {
 		t.Fatal(e)
 	case <-stopCh:
 	}
+
+	// Test the unsubscription of channel
+	common.Must(c.Unsubscribe(b))
+
+	// Test the last subscriber will close channel with `UnsubscribeClosableChannel`
+	common.Must(stats.UnsubscribeClosableChannel(c, a))
+	if c.Running() {
+		t.Fatal("unexpected running channel after unsubscribing the last subscriber")
+	}
 }
 
 func TestStatsChannelUnsubcribe(t *testing.T) {
-	raw, err := common.CreateObject(context.Background(), &Config{})
+	c := NewChannel(&ChannelConfig{})
-	common.Must(err)
+	common.Must(c.Start())
+	defer c.Close()
 
-	m := raw.(stats.Manager)
+	source := c.Channel()
-	c, err := m.RegisterChannel("test.channel")
-	common.Must(err)
-	common.Must(m.Start())
-	defer m.Close()
 
-	a := c.Subscribe()
+	a, err := c.Subscribe()
-	b := c.Subscribe()
+	common.Must(err)
 	defer c.Unsubscribe(a)
 
+	b, err := c.Subscribe()
+	common.Must(err)
+
 	pauseCh := make(chan struct{})
 	stopCh := make(chan struct{})
 	errCh := make(chan string)
@@ -119,10 +132,10 @@ func TestStatsChannelUnsubcribe(t *testing.T) {
 		}
 	}
 
-	go func() {
+	go func() { // Blocking publish
-		c.Publish(1)
+		source <- 1
 		<-pauseCh // Wait for `b` goroutine to resume sending message
-		c.Publish(2)
+		source <- 2
 	}()
 
 	go func() {
@@ -179,26 +192,27 @@ func TestStatsChannelUnsubcribe(t *testing.T) {
 }
 
 func TestStatsChannelTimeout(t *testing.T) {
-	raw, err := common.CreateObject(context.Background(), &Config{})
+	// Do not use buffer so as to create blocking scenario
-	common.Must(err)
+	c := NewChannel(&ChannelConfig{BufferSize: 0, BroadcastTimeout: 50})
+	common.Must(c.Start())
+	defer c.Close()
 
-	m := raw.(stats.Manager)
+	source := c.Channel()
-	c, err := m.RegisterChannel("test.channel")
-	common.Must(err)
-	common.Must(m.Start())
-	defer m.Close()
 
-	a := c.Subscribe()
+	a, err := c.Subscribe()
-	b := c.Subscribe()
+	common.Must(err)
 	defer c.Unsubscribe(a)
+
+	b, err := c.Subscribe()
+	common.Must(err)
 	defer c.Unsubscribe(b)
 
 	stopCh := make(chan struct{})
 	errCh := make(chan string)
 
-	go func() {
+	go func() { // Blocking publish
-		c.Publish(1)
+		source <- 1
-		c.Publish(2)
+		source <- 2
 	}()
 
 	go func() {
@@ -229,7 +243,7 @@ func TestStatsChannelTimeout(t *testing.T) {
 			errCh <- fmt.Sprint("unexpected receiving: ", v, ", wanted ", 1)
 		}
 		// Block `b` channel for a time longer than `source`'s timeout
-		<-time.After(150 * time.Millisecond)
+		<-time.After(200 * time.Millisecond)
 		{ // Test `b` has been unsubscribed by source
 			var aSet, bSet bool
 			for _, s := range c.Subscribers() {
@@ -264,25 +278,27 @@ func TestStatsChannelTimeout(t *testing.T) {
 }
 
 func TestStatsChannelConcurrency(t *testing.T) {
-	raw, err := common.CreateObject(context.Background(), &Config{})
+	// Do not use buffer so as to create blocking scenario
-	common.Must(err)
+	c := NewChannel(&ChannelConfig{BufferSize: 0, BroadcastTimeout: 100})
+	common.Must(c.Start())
+	defer c.Close()
 
-	m := raw.(stats.Manager)
+	source := c.Channel()
-	c, err := m.RegisterChannel("test.channel")
-	common.Must(err)
-	common.Must(m.Start())
-	defer m.Close()
 
-	a := c.Subscribe()
+	a, err := c.Subscribe()
-	b := c.Subscribe()
+	common.Must(err)
 	defer c.Unsubscribe(a)
 
+	b, err := c.Subscribe()
+	common.Must(err)
+	defer c.Unsubscribe(b)
+
 	stopCh := make(chan struct{})
 	errCh := make(chan string)
 
-	go func() {
+	go func() { // Blocking publish
-		c.Publish(1)
+		source <- 1
-		c.Publish(2)
+		source <- 2
 	}()
 
 	go func() {

app/stats/config.go

@@ -1,15 +0,0 @@
-// +build !confonly
-
-package stats
-
-import (
-	"context"
-
-	"v2ray.com/core/common"
-)
-
-func init() {
-	common.Must(common.RegisterConfig((*Config)(nil), func(ctx context.Context, config interface{}) (interface{}, error) {
-		return NewManager(ctx, config.(*Config))
-	}))
-}

app/stats/config.pb.go

@@ -63,18 +63,90 @@ func (*Config) Descriptor() ([]byte, []int) {
 	return file_app_stats_config_proto_rawDescGZIP(), []int{0}
 }
 
+type ChannelConfig struct {
+	state         protoimpl.MessageState
+	sizeCache     protoimpl.SizeCache
+	unknownFields protoimpl.UnknownFields
+
+	SubscriberLimit  int32 `protobuf:"varint,1,opt,name=SubscriberLimit,proto3" json:"SubscriberLimit,omitempty"`
+	BufferSize       int32 `protobuf:"varint,2,opt,name=BufferSize,proto3" json:"BufferSize,omitempty"`
+	BroadcastTimeout int32 `protobuf:"varint,3,opt,name=BroadcastTimeout,proto3" json:"BroadcastTimeout,omitempty"`
+}
+
+func (x *ChannelConfig) Reset() {
+	*x = ChannelConfig{}
+	if protoimpl.UnsafeEnabled {
+		mi := &file_app_stats_config_proto_msgTypes[1]
+		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
+		ms.StoreMessageInfo(mi)
+	}
+}
+
+func (x *ChannelConfig) String() string {
+	return protoimpl.X.MessageStringOf(x)
+}
+
+func (*ChannelConfig) ProtoMessage() {}
+
+func (x *ChannelConfig) ProtoReflect() protoreflect.Message {
+	mi := &file_app_stats_config_proto_msgTypes[1]
+	if protoimpl.UnsafeEnabled && x != nil {
+		ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
+		if ms.LoadMessageInfo() == nil {
+			ms.StoreMessageInfo(mi)
+		}
+		return ms
+	}
+	return mi.MessageOf(x)
+}
+
+// Deprecated: Use ChannelConfig.ProtoReflect.Descriptor instead.
+func (*ChannelConfig) Descriptor() ([]byte, []int) {
+	return file_app_stats_config_proto_rawDescGZIP(), []int{1}
+}
+
+func (x *ChannelConfig) GetSubscriberLimit() int32 {
+	if x != nil {
+		return x.SubscriberLimit
+	}
+	return 0
+}
+
+func (x *ChannelConfig) GetBufferSize() int32 {
+	if x != nil {
+		return x.BufferSize
+	}
+	return 0
+}
+
+func (x *ChannelConfig) GetBroadcastTimeout() int32 {
+	if x != nil {
+		return x.BroadcastTimeout
+	}
+	return 0
+}
+
 var File_app_stats_config_proto protoreflect.FileDescriptor
 
 var file_app_stats_config_proto_rawDesc = []byte{
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+	0x0a, 0x06, 0x43, 0x6f, 0x6e, 0x66, 0x69, 0x67, 0x22, 0x85, 0x01, 0x0a, 0x0d, 0x43, 0x68, 0x61,
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+	0x6e, 0x6e, 0x65, 0x6c, 0x43, 0x6f, 0x6e, 0x66, 0x69, 0x67, 0x12, 0x28, 0x0a, 0x0f, 0x53, 0x75,
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+	0x62, 0x73, 0x63, 0x72, 0x69, 0x62, 0x65, 0x72, 0x4c, 0x69, 0x6d, 0x69, 0x74, 0x18, 0x01, 0x20,
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+	0x01, 0x28, 0x05, 0x52, 0x0f, 0x53, 0x75, 0x62, 0x73, 0x63, 0x72, 0x69, 0x62, 0x65, 0x72, 0x4c,
-	0xaa, 0x02, 0x14, 0x56, 0x32, 0x52, 0x61, 0x79, 0x2e, 0x43, 0x6f, 0x72, 0x65, 0x2e, 0x41, 0x70,
+	0x69, 0x6d, 0x69, 0x74, 0x12, 0x1e, 0x0a, 0x0a, 0x42, 0x75, 0x66, 0x66, 0x65, 0x72, 0x53, 0x69,
-	0x70, 0x2e, 0x53, 0x74, 0x61, 0x74, 0x73, 0x62, 0x06, 0x70, 0x72, 0x6f, 0x74, 0x6f, 0x33,
+	0x7a, 0x65, 0x18, 0x02, 0x20, 0x01, 0x28, 0x05, 0x52, 0x0a, 0x42, 0x75, 0x66, 0x66, 0x65, 0x72,
+	0x53, 0x69, 0x7a, 0x65, 0x12, 0x2a, 0x0a, 0x10, 0x42, 0x72, 0x6f, 0x61, 0x64, 0x63, 0x61, 0x73,
+	0x74, 0x54, 0x69, 0x6d, 0x65, 0x6f, 0x75, 0x74, 0x18, 0x03, 0x20, 0x01, 0x28, 0x05, 0x52, 0x10,
+	0x42, 0x72, 0x6f, 0x61, 0x64, 0x63, 0x61, 0x73, 0x74, 0x54, 0x69, 0x6d, 0x65, 0x6f, 0x75, 0x74,
+	0x42, 0x4d, 0x0a, 0x18, 0x63, 0x6f, 0x6d, 0x2e, 0x76, 0x32, 0x72, 0x61, 0x79, 0x2e, 0x63, 0x6f,
+	0x72, 0x65, 0x2e, 0x61, 0x70, 0x70, 0x2e, 0x73, 0x74, 0x61, 0x74, 0x73, 0x50, 0x01, 0x5a, 0x18,
+	0x76, 0x32, 0x72, 0x61, 0x79, 0x2e, 0x63, 0x6f, 0x6d, 0x2f, 0x63, 0x6f, 0x72, 0x65, 0x2f, 0x61,
+	0x70, 0x70, 0x2f, 0x73, 0x74, 0x61, 0x74, 0x73, 0xaa, 0x02, 0x14, 0x56, 0x32, 0x52, 0x61, 0x79,
+	0x2e, 0x43, 0x6f, 0x72, 0x65, 0x2e, 0x41, 0x70, 0x70, 0x2e, 0x53, 0x74, 0x61, 0x74, 0x73, 0x62,
+	0x06, 0x70, 0x72, 0x6f, 0x74, 0x6f, 0x33,
 }
 
 var (
@@ -89,9 +161,10 @@ func file_app_stats_config_proto_rawDescGZIP() []byte {
 	return file_app_stats_config_proto_rawDescData
 }
 
-var file_app_stats_config_proto_msgTypes = make([]protoimpl.MessageInfo, 1)
+var file_app_stats_config_proto_msgTypes = make([]protoimpl.MessageInfo, 2)
 var file_app_stats_config_proto_goTypes = []interface{}{
 	(*Config)(nil),        // 0: v2ray.core.app.stats.Config
+	(*ChannelConfig)(nil), // 1: v2ray.core.app.stats.ChannelConfig
 }
 var file_app_stats_config_proto_depIdxs = []int32{
 	0, // [0:0] is the sub-list for method output_type
@@ -119,6 +192,18 @@ func file_app_stats_config_proto_init() {
 				return nil
 			}
 		}
+		file_app_stats_config_proto_msgTypes[1].Exporter = func(v interface{}, i int) interface{} {
+			switch v := v.(*ChannelConfig); i {
+			case 0:
+				return &v.state
+			case 1:
+				return &v.sizeCache
+			case 2:
+				return &v.unknownFields
+			default:
+				return nil
+			}
+		}
 	}
 	type x struct{}
 	out := protoimpl.TypeBuilder{
@@ -126,7 +211,7 @@ func file_app_stats_config_proto_init() {
 			GoPackagePath: reflect.TypeOf(x{}).PkgPath(),
 			RawDescriptor: file_app_stats_config_proto_rawDesc,
 			NumEnums:      0,
-			NumMessages:   1,
+			NumMessages:   2,
 			NumExtensions: 0,
 			NumServices:   0,
 		},

app/stats/config.proto

@@ -9,3 +9,9 @@ option java_multiple_files = true;
 message Config {
 
 }
+
+message ChannelConfig {
+    int32 SubscriberLimit = 1;
+    int32 BufferSize = 2;
+    int32 BroadcastTimeout = 3;
+}

app/stats/stats.go

@@ -8,6 +8,8 @@ import (
 	"context"
 	"sync"
 
+	"v2ray.com/core/common"
+	"v2ray.com/core/common/errors"
 	"v2ray.com/core/features/stats"
 )
 
@@ -92,10 +94,10 @@ func (m *Manager) RegisterChannel(name string) (stats.Channel, error) {
 		return nil, newError("Channel ", name, " already registered.")
 	}
 	newError("create new channel ", name).AtDebug().WriteToLog()
-	c := new(Channel)
+	c := NewChannel(&ChannelConfig{BufferSize: 16, BroadcastTimeout: 100})
 	m.channels[name] = c
 	if m.running {
-		c.Start()
+		return c, c.Start()
 	}
 	return c, nil
 }
@@ -108,7 +110,7 @@ func (m *Manager) UnregisterChannel(name string) error {
 	if c, found := m.channels[name]; found {
 		newError("remove channel ", name).AtDebug().WriteToLog()
 		delete(m.channels, name)
-		c.Close()
+		return c.Close()
 	}
 	return nil
 }
@@ -129,8 +131,14 @@ func (m *Manager) Start() error {
 	m.access.Lock()
 	defer m.access.Unlock()
 	m.running = true
+	errs := []error{}
 	for _, channel := range m.channels {
-		channel.Start()
+		if err := channel.Start(); err != nil {
+			errs = append(errs, err)
+		}
+	}
+	if len(errs) != 0 {
+		return errors.Combine(errs...)
 	}
 	return nil
 }
@@ -140,10 +148,22 @@ func (m *Manager) Close() error {
 	m.access.Lock()
 	defer m.access.Unlock()
 	m.running = false
+	errs := []error{}
 	for name, channel := range m.channels {
 		newError("remove channel ", name).AtDebug().WriteToLog()
 		delete(m.channels, name)
-		channel.Close()
+		if err := channel.Close(); err != nil {
+			errs = append(errs, err)
+		}
+	}
+	if len(errs) != 0 {
+		return errors.Combine(errs...)
 	}
 	return nil
 }
+
+func init() {
+	common.Must(common.RegisterConfig((*Config)(nil), func(ctx context.Context, config interface{}) (interface{}, error) {
+		return NewManager(ctx, config.(*Config))
+	}))
+}

app/stats/stats_test.go

@@ -42,7 +42,8 @@ func TestStatsChannelRunnable(t *testing.T) {
 		t.Fatalf("unexpected non-running channel: test.channel.%d", 2)
 	}
 
-	s1 := c1.Subscribe()
+	s1, err := c1.Subscribe()
+	common.Must(err)
 	common.Must(c1.Close())
 
 	if c1.Running() {

features/stats/stats.go

@@ -30,9 +30,30 @@ type Channel interface {
 	// SubscriberCount returns the number of the subscribers.
 	Subscribers() []chan interface{}
 	// Subscribe registers for listening to channel stream and returns a new listener channel.
-	Subscribe() chan interface{}
+	Subscribe() (chan interface{}, error)
 	// Unsubscribe unregisters a listener channel from current Channel object.
-	Unsubscribe(chan interface{})
+	Unsubscribe(chan interface{}) error
+}
+
+// SubscribeRunnableChannel subscribes the channel and starts it if there is first subscriber coming.
+func SubscribeRunnableChannel(c Channel) (chan interface{}, error) {
+	if len(c.Subscribers()) == 0 {
+		if err := c.Start(); err != nil {
+			return nil, err
+		}
+	}
+	return c.Subscribe()
+}
+
+// UnsubscribeClosableChannel unsubcribes the channel and close it if there is no more subscriber.
+func UnsubscribeClosableChannel(c Channel, sub chan interface{}) error {
+	if err := c.Unsubscribe(sub); err != nil {
+		return err
+	}
+	if len(c.Subscribers()) == 0 {
+		return c.Close()
+	}
+	return nil
 }
 
 // Manager is the interface for stats manager.