conn: send heartbeats to detect dead connections (#1258)

conn.go

@@ -256,6 +256,7 @@ func (s *Session) dial(host *HostInfo, cfg *ConnConfig, errorHandler ConnErrorHa
 	}
 
 	go c.serve()
+	go c.heartBeat()
 
 	return c, nil
 }
@@ -506,6 +507,53 @@ func (p *protocolError) Error() string {
 	return fmt.Sprintf("gocql: received unexpected frame on stream %d: %v", p.frame.Header().stream, p.frame)
 }
 
+func (c *Conn) heartBeat() {
+	sleepTime := 1 * time.Second
+	timer := time.NewTimer(sleepTime)
+	defer timer.Stop()
+
+	var failures int
+
+	for {
+		if failures > 5 {
+			c.closeWithError(fmt.Errorf("gocql: heartbeat failed"))
+			return
+		}
+
+		timer.Reset(sleepTime)
+
+		select {
+		case <-c.quit:
+			return
+		case <-timer.C:
+		}
+
+		framer, err := c.exec(context.Background(), &writeOptionsFrame{}, nil)
+		if err != nil {
+			failures++
+			continue
+		}
+
+		resp, err := framer.parseFrame()
+		if err != nil {
+			// invalid frame
+			failures++
+			continue
+		}
+
+		switch resp.(type) {
+		case *supportedFrame:
+			// Everything ok
+			sleepTime = 5 * time.Second
+			failures = 0
+		case error:
+			// TODO: should we do something here?
+		default:
+			panic(fmt.Sprintf("gocql: unknown frame in response to options: %T", resp))
+		}
+	}
+}
+
 func (c *Conn) recv() error {
 	// not safe for concurrent reads