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.bookkeeper.discover;
  
  import java.net.UnknownHostException;
  import java.util.Set;
  import java.util.concurrent.CompletableFuture;
  import org.apache.bookkeeper.common.annotation.InterfaceAudience.LimitedPrivate;
  import org.apache.bookkeeper.common.annotation.InterfaceStability.Evolving;
  import org.apache.bookkeeper.common.concurrent.FutureUtils;
  import org.apache.bookkeeper.net.BookieId;
  import org.apache.bookkeeper.versioning.LongVersion;
  import org.apache.bookkeeper.versioning.Versioned;
  
  /**
   * A registration client, which the bookkeeper client will use to interact with registration service.
   */
  
  @LimitedPrivate
  @Evolving
  public interface RegistrationClient extends AutoCloseable {
  
      /**
       * Listener to receive changes from the registration service.
       */
      interface RegistrationListener {
  
          void onBookiesChanged(Versioned<Set<BookieId>> bookies);
  
      }
  
      @Override
      void close();
  
      /**
       * Get the list of writable bookie identifiers.
       *
       * @return a future represents the list of writable bookies.
       */
      CompletableFuture<Versioned<Set<BookieId>>> getWritableBookies();
  
      /**
       * Get the list of all bookies identifiers.
       *
       * @return a future represents the list of all bookies.
       */
      CompletableFuture<Versioned<Set<BookieId>>> getAllBookies();
  
      /**
       * Get the list of readonly bookie identifiers.
       *
       * @return a future represents the list of readonly bookies.
       */
      CompletableFuture<Versioned<Set<BookieId>>> getReadOnlyBookies();
  
      /**
       * Get detailed information about the services exposed by a Bookie.
       * For old bookies it is expected to return an empty BookieServiceInfo structure.
       *
       * @param bookieId this is the id of the bookie, it can be computed from a {@link BookieId}
       * @return a future represents the available information.
       *
       * @since 4.11
       */
      default CompletableFuture<Versioned<BookieServiceInfo>> getBookieServiceInfo(BookieId bookieId) {
          try {
              BookieServiceInfo bookieServiceInfo = BookieServiceInfoUtils
                      .buildLegacyBookieServiceInfo(bookieId.toString());
              return FutureUtils.value(new Versioned<>(bookieServiceInfo, new LongVersion(-1)));
          } catch (UnknownHostException e) {
              return FutureUtils.exception(e);
          }
      }
  
      /**
       * Watch the changes of bookies.
       *
       * <p>The topology changes of bookies will be propagated to the provided <i>listener</i>.
       *
       * @param listener listener to receive the topology changes of bookies.
       * @return a future which completes when the bookies have been read for
       *         the first time
       */
      CompletableFuture<Void> watchWritableBookies(RegistrationListener listener);
  
      /**
       * Unwatch the changes of bookies.
       *
       * @param listener listener to receive the topology changes of bookies.
       */
      void unwatchWritableBookies(RegistrationListener listener);
  
      /**
       * Watch the changes of bookies.
       *
       * <p>The topology changes of bookies will be propagated to the provided <i>listener</i>.
       *
       * @param listener listener to receive the topology changes of bookies.
       * @return a future which completes when the bookies have been read for
       *         the first time
       */
      CompletableFuture<Void> watchReadOnlyBookies(RegistrationListener listener);
  
      /**
       * Unwatch the changes of bookies.
       *
       * @param listener listener to receive the topology changes of bookies.
       */
      void unwatchReadOnlyBookies(RegistrationListener listener);
  
  }
  