Make initial/max retry duration configurable

closes donovanhide#40

stream.go

@@ -18,7 +18,12 @@ type Stream struct {
 	c           *http.Client
 	req         *http.Request
 	lastEventId string
-	retry       time.Duration
+	// InitialRetryDelay indicates how long to wait before attempting to reconnect.
+	// This may be overridden by the server.
+	InitialRetryDelay time.Duration
+	// MaxRetryDelay specifies the maximum time to wait between consecutive
+	// reconnect attempts.
+	MaxRetryDelay time.Duration
 	// Events emits the events received by the stream
 	Events chan Event
 	// Errors emits any errors encountered while reading events from the stream.
@@ -63,12 +68,13 @@ func SubscribeWithRequest(lastEventId string, request *http.Request) (*Stream, e
 // control over the http client settings (timeouts, tls, etc)
 func SubscribeWith(lastEventId string, client *http.Client, request *http.Request) (*Stream, error) {
 	stream := &Stream{
-		c:           client,
-		req:         request,
-		lastEventId: lastEventId,
-		retry:       time.Millisecond * 3000,
-		Events:      make(chan Event),
-		Errors:      make(chan error),
+		c:                 client,
+		req:               request,
+		lastEventId:       lastEventId,
+		InitialRetryDelay: time.Millisecond * 3000,
+		MaxRetryDelay:     0,
+		Events:            make(chan Event),
+		Errors:            make(chan error),
 	}
 	stream.c.CheckRedirect = checkRedirect
 
@@ -163,7 +169,7 @@ func (stream *Stream) receiveEvents(r io.ReadCloser) {
 
 		pub := ev.(*publication)
 		if pub.Retry() > 0 {
-			stream.retry = time.Duration(pub.Retry()) * time.Millisecond
+			stream.InitialRetryDelay = time.Duration(pub.Retry()) * time.Millisecond
 		}
 		if len(pub.Id()) > 0 {
 			stream.lastEventId = pub.Id()
@@ -173,7 +179,7 @@ func (stream *Stream) receiveEvents(r io.ReadCloser) {
 }
 
 func (stream *Stream) retryRestartStream() {
-	backoff := stream.retry
+	backoff := stream.InitialRetryDelay
 	for {
 		if stream.Logger != nil {
 			stream.Logger.Printf("Reconnecting in %0.4f secs\n", backoff.Seconds())
@@ -192,5 +198,8 @@ func (stream *Stream) retryRestartStream() {
 		}
 		stream.Errors <- err
 		backoff *= 2
+		if stream.MaxRetryDelay > 0 && backoff > stream.MaxRetryDelay {
+			backoff = stream.MaxRetryDelay
+		}
 	}
 }