content: /*
   * Licensed to the Apache Software Foundation (ASF) under one
   * or more contributor license agreements.  See the NOTICE file
   * distributed with this work for additional information
   * regarding copyright ownership.  The ASF licenses this file
   * to you under the Apache License, Version 2.0 (the
   * "License"); you may not use this file except in compliance
   * with the License.  You may obtain a copy of the License at
   *
   *     http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  package org.apache.cassandra.locator;
  
  import java.net.UnknownHostException;
  import java.util.ArrayList;
  import java.util.Collections;
  import java.util.List;
  import java.util.Map;
  
  import com.google.common.annotations.VisibleForTesting;
  
  import org.apache.cassandra.config.CassandraRelevantProperties;
  import org.apache.cassandra.config.Config;
  import org.apache.cassandra.config.DatabaseDescriptor;
  import org.apache.cassandra.utils.FBUtilities;
  
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  public class SimpleSeedProvider implements SeedProvider
  {
      private static final Logger logger = LoggerFactory.getLogger(SimpleSeedProvider.class);
      @VisibleForTesting
      public static final String SEEDS_KEY = "seeds";
      @VisibleForTesting
      public static final String RESOLVE_MULTIPLE_IP_ADDRESSES_PER_DNS_RECORD_KEY = "resolve_multiple_ip_addresses_per_dns_record";
      private static final int SEED_COUNT_WARN_THRESHOLD = CassandraRelevantProperties.SEED_COUNT_WARN_THRESHOLD.getInt(20);
  
      private final String[] defaultSeeds;
  
      public SimpleSeedProvider(Map<String, String> args)
      {
          defaultSeeds = new String[] { FBUtilities.getLocalAddressAndPort().getHostAddress(true) };
      }
  
      public List<InetAddressAndPort> getSeeds()
      {
          Config conf;
          try
          {
              conf = DatabaseDescriptor.loadConfig();
          }
          catch (Exception e)
          {
              throw new AssertionError(e);
          }
  
          assert conf.seed_provider != null : "conf.seed_provider is null!";
  
          boolean resolveMultipleIps;
          String[] hosts;
  
          Map<String, String> parameters = conf.seed_provider.parameters;
          if (parameters == null)
          {
              resolveMultipleIps = false;
              hosts = defaultSeeds;
          }
          else
          {
              hosts = parameters.getOrDefault(SEEDS_KEY, defaultSeeds[0]).split(",", -1);
              resolveMultipleIps = Boolean.parseBoolean(parameters.getOrDefault(RESOLVE_MULTIPLE_IP_ADDRESSES_PER_DNS_RECORD_KEY, Boolean.FALSE.toString()));
          }
  
          List<InetAddressAndPort> seeds = new ArrayList<>(hosts.length);
  
          for (String host : hosts)
          {
              try
              {
                  if (!host.trim().isEmpty())
                  {
                      if (resolveMultipleIps)
                      {
                          List<InetAddressAndPort> resolvedSeeds = InetAddressAndPort.getAllByName(host.trim());
                          seeds.addAll(resolvedSeeds);
                          logger.debug("{} resolves to {}", host, resolvedSeeds);
                      }
                      else
                      {
                          InetAddressAndPort addressAndPort = InetAddressAndPort.getByName(host.trim());
                          seeds.add(addressAndPort);
                          logger.debug("Only resolving one IP per DNS record - {} resolves to {}", host, addressAndPort);
                      }
                  }
              }
              catch (UnknownHostException ex)
              {
                  // not fatal... DD will bark if there end up being zero seeds.
                  logger.warn("Seed provider couldn't lookup host {}", host);
              }
          }
  
          if (seeds.size() > SEED_COUNT_WARN_THRESHOLD)
              logger.warn("Seed provider returned more than {} seeds. " +
                          "A large seed list may impact effectiveness of the third gossip round.",
                          SEED_COUNT_WARN_THRESHOLD);
  
          return Collections.unmodifiableList(seeds);
      }
  }
  