feat: agents connect by WebSocket, falling back to long polling and trying again each minute; auto, ws or lp per machine (0.1.0)

internal/server/hub.go

@@ -275,6 +275,18 @@ func (s *Session) PushIn(f proto.InFrame) {
 	}
 }
 
+// Unpoll puts frames taken by PollIn back in front, for frames that could not
+// be delivered.
+func (s *Session) Unpoll(frames []proto.InFrame) {
+	s.mu.Lock()
+	s.inBuf = append(append([]proto.InFrame{}, frames...), s.inBuf...)
+	s.mu.Unlock()
+	select {
+	case s.inSignal <- struct{}{}:
+	default:
+	}
+}
+
 // PollIn drains queued downstream frames, blocking up to timeout for the first.
 func (s *Session) PollIn(timeout time.Duration) ([]proto.InFrame, bool) {
 	deadline := time.After(timeout)