@Override
  protected void regionMoved(int region, int oldServer, int newServer) {
    int tableIdx = cluster.regionIndexToTableIndex[region];
    costsPerTable[tableIdx].applyCostsChange(costs -> {
      costs[oldServer] = cluster.numRegionsPerServerPerTable[tableIdx][oldServer];
      costs[newServer] = cluster.numRegionsPerServerPerTable[tableIdx][newServer];
    });
  }
Compute the cost of a potential cluster configuration based upon how evenly distributed tables
are.
hbase-balancer/src/main/java/org/apache/hadoop/hbase/master/balancer/TableSkewCostFunction.java