in docker/ops-playground-image/java/flink-playground-clickcountjob/src/main/java/org/apache/flink/playgrounds/ops/clickcount/ClickEventGenerator.java [106:110]
private Date nextTimestamp(String page) {
long nextTimestamp = nextTimestampPerKey.getOrDefault(page, 0L);
nextTimestampPerKey.put(page, nextTimestamp + WINDOW_SIZE.toMilliseconds() / EVENTS_PER_WINDOW);
return new Date(nextTimestamp);
}