fixed a couple of issues flagged by coderabbit

Signed-off-by: Dmitri Dolguikh <dmitri.external@netbird.io>

client/internal/netflow/manager.go

@@ -223,12 +223,12 @@ func (m *Manager) startSender(ctx context.Context, flowConfigInterval time.Durat
 			collectedEvents := m.logger.ResetAggregationWindow()
 			events := collectedEvents.GetAggregatedEvents()
 			for _, event := range events {
+				m.eventsWithoutAcks.StoreEvent(event)
 				if err := m.send(event); err != nil {
 					log.Errorf("failed to send flow event to server: %v", err)
 				} else {
 					log.Tracef("sent flow event: %s", event.ID)
 				}
-				m.eventsWithoutAcks.StoreEvent(event)
 			}
 		}
 	}
@@ -271,6 +271,7 @@ func (m *Manager) startRetries(ctx context.Context, flowConfigInterval time.Dura
 		case <-ctx.Done():
 			return
 		case <-timer.C:
+			resetBackoff := true
 			for _, e := range m.eventsWithoutAcks.GetEvents() {
 				if e.Timestamp.Add(time.Second).After(time.Now()) {
 					// grace period on retries to avoid early retries
@@ -278,12 +279,15 @@ func (m *Manager) startRetries(ctx context.Context, flowConfigInterval time.Dura
 					continue
 				}
 				if err := m.send(e); err != nil {
-					timer = time.NewTimer(retryBackoff.NextBackOff()) //nolint:staticcheck,wastedassign
+					timer = time.NewTimer(retryBackoff.NextBackOff())
+					resetBackoff = false
 					break
 				}
 			}
-			retryBackoff.Reset()
+			if resetBackoff { // use regular retry interval in absense of network errors
-			timer = time.NewTimer(m.retryInterval)
+				retryBackoff.Reset()
+				timer = time.NewTimer(m.retryInterval)
+			}
 		}
 	}
 }

client/internal/netflow/store/memory.go

@@ -70,7 +70,7 @@ func (am *AggregatingMemory) ResetAggregationWindow() types.FlowEventAggregator
 	defer am.mux.Unlock()
 
 	now := time.Now()
-	toret := AggregatingMemory{WindowStart: am.WindowStart, WindowEnd: now, Memory: Memory{events: am.events}}
+	toret := AggregatingMemory{WindowStart: am.WindowStart, WindowEnd: now, Memory: Memory{events: am.events}, rnd: v2.NewPCG(rand.Uint64(), rand.Uint64())}
 
 	am.events = make(map[uuid.UUID]*types.Event)
 	am.WindowStart = now

flow/client/client.go

@@ -109,7 +109,7 @@ func (c *GRPCClient) Close() error {
 func (c *GRPCClient) Send(event *proto.FlowEvent) error {
 	c.mu.Lock()
 	stream := c.stream
-	c.mu.Unlock()
+	defer c.mu.Unlock() // stream.Send() is not safe to call concurrently from multiple goroutines
 
 	if stream == nil {
 		return errors.New("stream not initialized")