@Override
  public HostPartitionClassStorageStatsWrapper queryHostPartitionClassStorageStatsByHost(String hostname, int port,
      Map<String, Set<Integer>> partitionNameAndIds) {
    return partitionStatsMap.get(hostname + "_" + port);
  }
Constructor to instantiate an {@link InmemoryAccountStatsStore}.
@param clusterName the clusterName
@param hostname the hostname
ambry-mysql/src/main/java/com/github/ambry/accountstats/InmemoryAccountStatsStore.java