private LoadingCache<RegionInfo, HDFSBlocksDistribution> createCache() {
    return CacheBuilder.newBuilder().expireAfterWrite(CACHE_TIME, TimeUnit.MILLISECONDS)
      .build(loader);
  }
Create a cache for region to list of servers
@return A new Cache.
hbase-balancer/src/main/java/org/apache/hadoop/hbase/master/balancer/RegionHDFSBlockLocationFinder.java