private synchronized void init() {
    startTime = EnvironmentEdgeManager.currentTime();
    prevTime = startTime;
    blockedRequestCount = region.getBlockedRequestsCount();
    writeRequestCount = region.getWriteRequestsCount();
  }
This class represents a split policy which makes the split decision based on how busy a region
is. The metric that is used here is the fraction of total write requests that are blocked due to
high memstore utilization. This fractional rate is calculated over a running window of
"hbase.busy.policy.aggWindow" milliseconds. The rate is a time-weighted aggregated average of the
rate in the current window and the true average rate in the previous window.
hbase-server/src/main/java/org/apache/hadoop/hbase/regionserver/BusyRegionSplitPolicy.java