Add MaxConnectRetryInterval client option for reconnect exponential b…

…ackoff related to eclipse-paho#589

Signed-off-by: Daichi Tomaru <[email protected]>

client.go

@@ -255,17 +255,26 @@ func (c *client) Connect() Token {
 			return
 		}
 
+	connectRetryInterval := c.options.ConnectRetryInterval
 	RETRYCONN:
 		var conn net.Conn
 		var rc byte
 		var err error
 		conn, rc, t.sessionPresent, err = c.attemptConnection()
 		if err != nil {
 			if c.options.ConnectRetry {
-				DEBUG.Println(CLI, "Connect failed, sleeping for", int(c.options.ConnectRetryInterval.Seconds()), "seconds and will then retry, error:", err.Error())
-				time.Sleep(c.options.ConnectRetryInterval)
+				DEBUG.Println(CLI, "Connect failed, sleeping for", int(connectRetryInterval.Seconds()), "seconds and will then retry, error:", err.Error())
+				time.Sleep(connectRetryInterval)
 
 				if c.status.ConnectionStatus() == connecting { // Possible connection aborted elsewhere
+					if c.options.ConnectRetryInterval >= c.options.MaxConnectRetryInterval {
+						goto RETRYCONN
+					}
+					if cri := connectRetryInterval * 2; cri <= c.options.MaxConnectRetryInterval {
+						connectRetryInterval = cri
+					} else {
+						connectRetryInterval = c.options.MaxConnectRetryInterval
+					}
 					goto RETRYCONN
 				}
 			}

options.go

@@ -88,6 +88,7 @@ type ClientOptions struct {
 	ConnectTimeout          time.Duration
 	MaxReconnectInterval    time.Duration
 	AutoReconnect           bool
+	MaxConnectRetryInterval time.Duration
 	ConnectRetryInterval    time.Duration
 	ConnectRetry            bool
 	Store                   Store
@@ -136,6 +137,7 @@ func NewClientOptions() *ClientOptions {
 		ConnectTimeout:          30 * time.Second,
 		MaxReconnectInterval:    10 * time.Minute,
 		AutoReconnect:           true,
+		MaxConnectRetryInterval: 30 * time.Second,
 		ConnectRetryInterval:    30 * time.Second,
 		ConnectRetry:            false,
 		Store:                   nil,
@@ -386,6 +388,14 @@ func (o *ClientOptions) SetAutoReconnect(a bool) *ClientOptions {
 	return o
 }
 
+// SetMaxConnectRetryInterval sets the maximum time that will be waited between connection attempts
+// when initially connecting if ConnectRetry is TRUE
+// If ConnectRetryInterval >= MaxConnectRetryInterval, ConnectRetryInterval is kept between the attempts
+func (o *ClientOptions) SetMaxConnectRetryInterval(t time.Duration) *ClientOptions {
+	o.MaxConnectRetryInterval = t
+	return o
+}
+
 // SetConnectRetryInterval sets the time that will be waited between connection attempts
 // when initially connecting if ConnectRetry is TRUE
 func (o *ClientOptions) SetConnectRetryInterval(t time.Duration) *ClientOptions {

options_reader.go

@@ -137,6 +137,11 @@ func (r *ClientOptionsReader) AutoReconnect() bool {
 	return s
 }
 
+func (r *ClientOptionsReader) MaxConnectRetryInterval() time.Duration {
+	s := r.options.MaxConnectRetryInterval
+	return s
+}
+
 // ConnectRetryInterval returns the delay between retries on the initial connection (if ConnectRetry true)
 func (r *ClientOptionsReader) ConnectRetryInterval() time.Duration {
 	s := r.options.ConnectRetryInterval