/**
   * Writes out a bunch of mutations for a single column family.
   *
   * @param mutations A group of Mutations for the same keyspace and column family.
   * @return The ColumnFamilyStore that was used.
   */
  public static ColumnFamilyStore writeColumnFamily(List<Mutation> mutations) {
    IMutation first = mutations.get(0);
    String keyspaceName = first.getKeyspaceName();
    UUID cfid = first.getColumnFamilyIds().iterator().next();

    for (Mutation rm : mutations) rm.applyUnsafe();

    ColumnFamilyStore store = Keyspace.open(keyspaceName).getColumnFamilyStore(cfid);
    store.forceBlockingFlush();
    return store;
  }
  /** Creates initial set of nodes and tokens. Nodes are added to StorageService as 'normal' */
  public static void createInitialRing(
      StorageService ss,
      IPartitioner partitioner,
      List<Token> endpointTokens,
      List<Token> keyTokens,
      List<InetAddress> hosts,
      List<UUID> hostIds,
      int howMany)
      throws UnknownHostException {
    // Expand pool of host IDs as necessary
    for (int i = hostIdPool.size(); i < howMany; i++) hostIdPool.add(UUID.randomUUID());

    for (int i = 0; i < howMany; i++) {
      endpointTokens.add(new BigIntegerToken(String.valueOf(10 * i)));
      keyTokens.add(new BigIntegerToken(String.valueOf(10 * i + 5)));
      hostIds.add(hostIdPool.get(i));
    }

    for (int i = 0; i < endpointTokens.size(); i++) {
      InetAddress ep = InetAddress.getByName("127.0.0." + String.valueOf(i + 1));
      Gossiper.instance.initializeNodeUnsafe(ep, hostIds.get(i), 1);
      Gossiper.instance.injectApplicationState(
          ep,
          ApplicationState.TOKENS,
          new VersionedValue.VersionedValueFactory(partitioner)
              .tokens(Collections.singleton(endpointTokens.get(i))));
      ss.onChange(
          ep,
          ApplicationState.STATUS,
          new VersionedValue.VersionedValueFactory(partitioner)
              .normal(Collections.singleton(endpointTokens.get(i))));
      hosts.add(ep);
    }

    // check that all nodes are in token metadata
    for (int i = 0; i < endpointTokens.size(); ++i)
      assertTrue(ss.getTokenMetadata().isMember(hosts.get(i)));
  }