Learning Apache Apex

The windowing example

Examples for an augmented word count that show the use of windowing for both, the low-level DAG API and the high-level stream API, can be found at https://github.com/tweise/apex-samples/tree/master/windowing.

The following code block shows the DAG construction for a keyed sum aggregation over a fixed time window of one minute that emits the intermediate sum every second and the final result at the watermark:

public void populateDAG(DAG dag, Configuration configuration)   {     WordGenerator inputOperator = new WordGenerator();     KeyedWindowedOperatorImpl<String, Long, MutableLong,        Long> windowedOperator =       new KeyedWindowedOperatorImpl<>();     Accumulation<Long, MutableLong, Long> sum = new SumAccumulation();  windowedOperator.setAccumulation(sum); ...