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 com.datastax.oss.driver.internal.core.loadbalancing;
  
  import com.datastax.oss.driver.api.core.config.DefaultDriverOption;
  import com.datastax.oss.driver.api.core.context.DriverContext;
  import com.datastax.oss.driver.api.core.loadbalancing.LoadBalancingPolicy;
  import com.datastax.oss.driver.api.core.metadata.Node;
  import com.datastax.oss.driver.internal.core.loadbalancing.helper.InferringLocalDcHelper;
  import edu.umd.cs.findbugs.annotations.NonNull;
  import java.util.Map;
  import java.util.Optional;
  import java.util.UUID;
  import net.jcip.annotations.ThreadSafe;
  
  /**
   * An implementation of {@link LoadBalancingPolicy} that infers the local datacenter from the
   * contact points, if no datacenter was provided neither through configuration nor programmatically.
   *
   * <p>To activate this policy, modify the {@code basic.load-balancing-policy} section in the driver
   * configuration, for example:
   *
   * <pre>
   * datastax-java-driver {
   *   basic.load-balancing-policy {
   *     class = DcInferringLoadBalancingPolicy
   *     local-datacenter = datacenter1 # optional
   *   }
   * }
   * </pre>
   *
   * See {@code reference.conf} (in the manual or core driver JAR) for more details.
   *
   * <p><b>Local datacenter</b>: This implementation requires a local datacenter to be defined,
   * otherwise it will throw an {@link IllegalStateException}. A local datacenter can be supplied
   * either:
   *
   * <ol>
   *   <li>Programmatically with {@link
   *       com.datastax.oss.driver.api.core.session.SessionBuilder#withLocalDatacenter(String)
   *       SessionBuilder#withLocalDatacenter(String)};
   *   <li>Through configuration, by defining the option {@link
   *       DefaultDriverOption#LOAD_BALANCING_LOCAL_DATACENTER
   *       basic.load-balancing-policy.local-datacenter};
   *   <li>Or implicitly: in this case this implementation will infer the local datacenter from the
   *       provided contact points, if and only if they are all located in the same datacenter.
   * </ol>
   *
   * <p><b>Query plan</b>: see {@link DefaultLoadBalancingPolicy} for details on the computation of
   * query plans.
   *
   * <p><b>This class is not recommended for normal users who should always prefer {@link
   * DefaultLoadBalancingPolicy}</b>.
   */
  @ThreadSafe
  public class DcInferringLoadBalancingPolicy extends DefaultLoadBalancingPolicy {
  
    public DcInferringLoadBalancingPolicy(
        @NonNull DriverContext context, @NonNull String profileName) {
      super(context, profileName);
    }
  
    @NonNull
    @Override
    protected Optional<String> discoverLocalDc(@NonNull Map<UUID, Node> nodes) {
      return new InferringLocalDcHelper(context, profile, logPrefix).discoverLocalDc(nodes);
    }
  }
  