private long calculateMaxSteps(BalancerClusterState cluster) {
    return (long) cluster.numRegions * (long) this.stepsPerRegion * (long) cluster.numServers;
  }
Select the candidate generator to use based on the cost of cost functions. The chance of
selecting a candidate generator is proportional to the share of cost of all cost functions
among all cost functions that benefit from it.
hbase-balancer/src/main/java/org/apache/hadoop/hbase/master/balancer/StochasticLoadBalancer.java