@Override
      public ReturnCode canTakeRow(HRegionLocation loc, Row row) {
        if (isEnd) {
          return ReturnCode.END;
        }
        long heapSizeOfRow = (row instanceof Mutation) ? ((Mutation) row).heapSize() : 0;
        ReturnCode code = ReturnCode.INCLUDE;
        for (RowChecker checker : checkers) {
          switch (checker.canTakeOperation(loc, heapSizeOfRow)) {
            case END:
              isEnd = true;
              code = ReturnCode.END;
              break;
            case SKIP:
              code = ReturnCode.SKIP;
              break;
            case INCLUDE:
            default:
              break;
          }
          if (code == ReturnCode.END) {
            break;
          }
        }
        for (RowChecker checker : checkers) {
          checker.notifyFinal(code, loc, heapSizeOfRow);
        }
        return code;
      }
The number of task simultaneously executed on a single region server.
hbase-client/src/main/java/org/apache/hadoop/hbase/client/SimpleRequestController.java