fix: close redis proxy connection ID tracker on goroutine end (#520)

Signed-off-by: Jonathan West <[email protected]>

Author: jgwest

principal/event.go

@@ -377,6 +377,11 @@ func (s *Server) processRedisEventResponse(ctx context.Context, logCtx *logrus.E
 		// PushFromSubscribe is asynchronous, so we can't use event id tracker to find the corresponding channel.
 		// - We instead use connection id, which maps directly to the connection from Argo CD
 		trAgent, evChan := s.redisProxy.ConnectionIDTracker.Tracked(resReq.ConnectionUUID)
+		if evChan == nil {
+			logCtx.Debug("connection UUID is no longer in connectionIDTracker, likely the principal connection has closed")
+			return nil
+		}
+
 		if trAgent != agentName {
 			err := fmt.Errorf("agent mismap between event and tracking for PushFromSubscribe: '%s' '%s' '%s'", trAgent, agentName, resReq.ConnectionUUID)
 			return err

principal/redisproxy/redisproxy.go

@@ -458,6 +458,11 @@ func (rp *RedisProxy) handleAgentSubscribe(connState *connectionState, channelNa
 		// Forward all events from 'subscriptionChannel' to 'connectionUUIDEventsChannel'
 		go func() {
 			defer close(connState.connectionUUIDEventsChannel)
+			defer func() {
+				if err := rp.ConnectionIDTracker.StopTracking(connState.connUUID); err != nil {
+					logCtx.WithError(err).Error("connection ID tracker reported an unexpected error. At this stage of the goroutine lifecycle, the resource should still necessarily be tracked.")
+				}
+			}()
 
 			for {
 				select {