Add ReconnectClient (#18)

* Add ReconnectClient
* Temporary implement incremental wait
* Implement auto resubscribe
* Add Client.Handle

client.go

@@ -10,11 +10,10 @@ import (
 type BaseClient struct {
 	// Transport is an underlying connection. Typically net.Conn.
 	Transport io.ReadWriteCloser
-	// Handler of incoming messages.
-	Handler Handler
 	// ConnState is called if the connection state is changed.
 	ConnState func(ConnState, error)
 
+	handler    Handler
 	sig        *signaller
 	mu         sync.RWMutex
 	connState  ConnState
@@ -24,6 +23,13 @@ type BaseClient struct {
 	idLast     uint32
 }
 
+// Handle registers the message handler.
+func (c *BaseClient) Handle(handler Handler) {
+	c.mu.Lock()
+	defer c.mu.Unlock()
+	c.handler = handler
+}
+
 // WithUserNamePassword sets plain text auth information used in Connect.
 func WithUserNamePassword(userName, password string) ConnectOption {
 	return func(o *ConnectOptions) error {

client_integration_test.go

@@ -27,16 +27,17 @@ func ExampleClient() {
 	if err != nil {
 		panic(err)
 	}
-	baseCli.Handler = HandlerFunc(func(msg *Message) {
-		fmt.Printf("%s[%d]: %s", msg.Topic, int(msg.QoS), []byte(msg.Payload))
-		close(done)
-	})
 
 	// store as Client to make it easy to enable high level wrapper later
 	var cli Client = baseCli
 	ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
 	defer cancel()
 
+	cli.Handle(HandlerFunc(func(msg *Message) {
+		fmt.Printf("%s[%d]: %s", msg.Topic, int(msg.QoS), []byte(msg.Payload))
+		close(done)
+	}))
+
 	if _, err := cli.Connect(ctx, "TestClient", WithCleanSession(true)); err != nil {
 		panic(err)
 	}
@@ -123,9 +124,6 @@ func TestIntegration_PublishQoS2_SubscribeQoS2(t *testing.T) {
 			}
 
 			chReceived := make(chan *Message, 100)
-			cli.Handler = HandlerFunc(func(msg *Message) {
-				chReceived <- msg
-			})
 			cli.ConnState = func(s ConnState, err error) {
 				switch s {
 				case StateActive:
@@ -142,6 +140,10 @@ func TestIntegration_PublishQoS2_SubscribeQoS2(t *testing.T) {
 				t.Fatalf("Unexpected error: '%v'", err)
 			}
 
+			cli.Handle(HandlerFunc(func(msg *Message) {
+				chReceived <- msg
+			}))
+
 			if err := cli.Subscribe(ctx, Subscription{Topic: "test", QoS: QoS2}); err != nil {
 				t.Fatalf("Unexpected error: '%v'", err)
 			}
@@ -155,6 +157,8 @@ func TestIntegration_PublishQoS2_SubscribeQoS2(t *testing.T) {
 			}
 
 			select {
+			case <-ctx.Done():
+				t.Fatalf("Unexpected error: '%v'", ctx.Err())
 			case msg, ok := <-chReceived:
 				if !ok {
 					t.Errorf("Connection closed unexpectedly")
@@ -238,9 +242,6 @@ func BenchmarkPublishSubscribe(b *testing.B) {
 			}
 
 			chReceived := make(chan *Message, 100)
-			cli.Handler = HandlerFunc(func(msg *Message) {
-				chReceived <- msg
-			})
 			cli.ConnState = func(s ConnState, err error) {
 				switch s {
 				case StateActive:
@@ -256,6 +257,10 @@ func BenchmarkPublishSubscribe(b *testing.B) {
 				b.Fatalf("Unexpected error: '%v'", err)
 			}
 
+			cli.Handle(HandlerFunc(func(msg *Message) {
+				chReceived <- msg
+			}))
+
 			if err := cli.Subscribe(ctx, Subscription{Topic: "test", QoS: QoS2}); err != nil {
 				b.Fatalf("Unexpected error: '%v'", err)
 			}

conn.go

@@ -16,6 +16,22 @@ var ErrUnsupportedProtocol = errors.New("unsupported protocol")
 // ErrClosedTransport means that the underlying connection is closed.
 var ErrClosedTransport = errors.New("read/write on closed transport")
 
+// URLDialer is a Dialer using URL string.
+type URLDialer struct {
+	URL     string
+	Options []DialOption
+}
+
+// Dialer is an interface to create connection.
+type Dialer interface {
+	Dial() (ClientCloser, error)
+}
+
+// Dial creates connection using its values.
+func (d *URLDialer) Dial() (ClientCloser, error) {
+	return Dial(d.URL, d.Options...)
+}
+
 // Dial creates MQTT client using URL string.
 func Dial(urlStr string, opts ...DialOption) (*BaseClient, error) {
 	o := &DialOptions{
@@ -113,3 +129,15 @@ func (c *BaseClient) connStateUpdate(newState ConnState) {
 func (c *BaseClient) Close() error {
 	return c.Transport.Close()
 }
+
+// Done is a channel to signal connection close.
+func (c *BaseClient) Done() <-chan struct{} {
+	return c.connClosed
+}
+
+// Err returns connection error.
+func (c *BaseClient) Err() error {
+	c.mu.Lock()
+	defer c.mu.Unlock()
+	return c.err
+}

mqtt.go

@@ -51,11 +51,14 @@ type Client interface {
 	Subscribe(ctx context.Context, subs ...Subscription) error
 	Unsubscribe(ctx context.Context, subs ...string) error
 	Ping(ctx context.Context) error
+	Handle(Handler)
 }
 
 // Closer is the interface of connection closer.
 type Closer interface {
 	Close() error
+	Done() <-chan struct{}
+	Err() error
 }
 
 // ClientCloser groups Client and Closer interface

reconnclient.go

@@ -0,0 +1,72 @@
+package mqtt
+
+import (
+	"context"
+	"sync"
+	"time"
+)
+
+type reconnectClient struct {
+	Client
+}
+
+// NewReconnectClient creates a MQTT client with re-connect/re-publish/re-subscribe features.
+func NewReconnectClient(ctx context.Context, dialer Dialer, clientID string, opts ...ConnectOption) Client {
+	rc := &RetryClient{}
+	cli := &reconnectClient{
+		Client: rc,
+	}
+	done := make(chan struct{})
+	var doneOnce sync.Once
+	go func() {
+		clean := true
+		reconnWaitBase := 50 * time.Millisecond
+		reconnWaitMax := 10 * time.Second
+		reconnWait := reconnWaitBase
+		for {
+			if c, err := dialer.Dial(); err == nil {
+				optsCurr := append([]ConnectOption{}, opts...)
+				optsCurr = append(optsCurr, WithCleanSession(clean))
+				clean = false               // Clean only first time.
+				reconnWait = reconnWaitBase // Reset reconnect wait.
+				rc.SetClient(ctx, c)
+
+				if present, err := rc.Connect(ctx, clientID, optsCurr...); err == nil {
+					doneOnce.Do(func() { close(done) })
+					if present {
+						rc.Resubscribe(ctx)
+					}
+					// Start keep alive.
+					go func() {
+						_ = KeepAlive(ctx, c, time.Second, time.Second)
+					}()
+					select {
+					case <-c.Done():
+						if err := c.Err(); err == nil {
+							// Disconnected as expected; don't restart.
+							return
+						}
+					case <-ctx.Done():
+						// User cancelled; don't restart.
+						return
+					}
+				}
+			}
+			select {
+			case <-time.After(reconnWait):
+			case <-ctx.Done():
+				// User cancelled; don't restart.
+				return
+			}
+			reconnWait *= 2
+			if reconnWait > reconnWaitMax {
+				reconnWait = reconnWaitMax
+			}
+		}
+	}()
+	select {
+	case <-done:
+	case <-ctx.Done():
+	}
+	return cli
+}

reconnclient_integration_test.go

@@ -0,0 +1,58 @@
+// +build integration
+
+package mqtt
+
+import (
+	"context"
+	"crypto/tls"
+	"testing"
+	"time"
+)
+
+func TestIntegration_ReconnectClient(t *testing.T) {
+	for name, url := range urls {
+		t.Run(name, func(t *testing.T) {
+			ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
+			defer cancel()
+
+			chReceived := make(chan *Message, 100)
+			cli := NewReconnectClient(
+				ctx,
+				&URLDialer{
+					URL: url,
+					Options: []DialOption{
+						WithTLSConfig(&tls.Config{InsecureSkipVerify: true}),
+					},
+				},
+				"ReconnectClient",
+			)
+			cli.Handle(HandlerFunc(func(msg *Message) {
+				chReceived <- msg
+			}))
+
+			// Close underlying client.
+			cli.(*reconnectClient).Client.(*RetryClient).Client.(ClientCloser).Close()
+
+			if err := cli.Subscribe(ctx, Subscription{Topic: "test", QoS: QoS1}); err != nil {
+				t.Fatalf("Unexpected error: '%v'", err)
+			}
+			if err := cli.Publish(ctx, &Message{
+				Topic:   "test",
+				QoS:     QoS1,
+				Retain:  true,
+				Payload: []byte("message"),
+			}); err != nil {
+				t.Fatalf("Unexpected error: '%v'", err)
+			}
+
+			time.Sleep(time.Second)
+
+			select {
+			case <-ctx.Done():
+				t.Fatalf("Unexpected error: '%v'", ctx.Err())
+			case <-chReceived:
+			}
+		})
+	}
+
+}