docs: @Override
      synchronized int flush(long txnId)
      {
          int offered = 0;
          if (m_currentReads.containsKey(txnId)) {
              m_currentReads.remove(txnId);
              m_sitePool.completeWork(txnId);
          }
          else {
              assert(m_currentWrites.containsKey(txnId));
              m_currentWrites.remove(txnId);
              assert(m_currentWrites.isEmpty());
          }
          if (taskQueueOffer()) {
              ++offered;
          }
          return offered;
      }