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.kafka.common.replica;
  
  import org.apache.kafka.common.Configurable;
  import org.apache.kafka.common.TopicPartition;
  
  import java.io.Closeable;
  import java.io.IOException;
  import java.util.Map;
  import java.util.Optional;
  
  /**
   * Plug-able interface for selecting a preferred read replica given the current set of replicas for a partition
   * and metadata from the client.
   * Implement {@link org.apache.kafka.common.metrics.Monitorable} to enable the selector to register metrics.
   * The following tags are automatically added to all metrics registered: <code>config</code> set to
   * <code>replica.selector.class</code>, and <code>class</code> set to the ReplicaSelector class name.
   */
  public interface ReplicaSelector extends Configurable, Closeable {
  
      /**
       * Select the preferred replica a client should use for fetching. If no replica is available, this will return an
       * empty optional.
       */
      Optional<ReplicaView> select(TopicPartition topicPartition,
                                   ClientMetadata clientMetadata,
                                   PartitionView partitionView);
      @Override
      default void close() throws IOException {
          // No-op by default
      }
  
      @Override
      default void configure(Map<String, ?> configs) {
          // No-op by default
      }
  }
  