totalMessages  int64
	failedMessages int64

	wg sync.WaitGroup

	// Channel of log entries.
	// Reading logCh must hold read lock on logChMu (to avoid read race)
	// Sending a value on logCh must hold read lock on logChMu (to avoid closing)
	logCh   chan interface{}
	logChMu sync.RWMutex

	// store to persist and replay the logs to the target
	// to avoid missing events when the target is down.