basic-lib/src/main/java/com/streamsets/pipeline/stage/processor/aggregation/aggregator/Aggregators.java
public Map<Aggregator, AggregatorData> roll(long newDataWindowEndTimeMillis) {
    Utils.checkState(started, "Not started");
    Utils.checkState(!stopped, "Already stopped");
    return dataProvider.roll(newDataWindowEndTimeMillis);
  }
public Map<Aggregator, AggregatorData> roll(long newDataWindowEndTimeMillis) {
    Utils.checkState(started, "Not started");
    Utils.checkState(!stopped, "Already stopped");
    return dataProvider.roll(newDataWindowEndTimeMillis);
  }
Atomically rolls the DataWindow of all aggregators associated with the Aggregators instance.

@param newDataWindowEndTimeMillis ending time of the new DataWindow.
@return a Map with all the aggregators data of the DataWindow that closed.