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.grpc.resolver;
  
  import static com.google.common.base.Preconditions.checkState;
  
  import com.google.common.util.concurrent.ThreadFactoryBuilder;
  import io.grpc.Attributes;
  import io.grpc.EquivalentAddressGroup;
  import io.grpc.NameResolver;
  import java.net.URI;
  import java.util.Collections;
  import java.util.List;
  import java.util.Objects;
  import java.util.Optional;
  import java.util.Set;
  import java.util.concurrent.Executors;
  import java.util.concurrent.ScheduledExecutorService;
  import java.util.stream.Collectors;
  import org.apache.bookkeeper.client.BookieAddressResolverDisabled;
  import org.apache.bookkeeper.client.DefaultBookieAddressResolver;
  import org.apache.bookkeeper.conf.ClientConfiguration;
  import org.apache.bookkeeper.meta.MetadataClientDriver;
  import org.apache.bookkeeper.meta.exceptions.MetadataException;
  import org.apache.bookkeeper.net.BookieId;
  import org.apache.bookkeeper.proto.BookieAddressResolver;
  import org.apache.bookkeeper.stats.NullStatsLogger;
  
  /**
   * A {@link NameResolver} implementation based on bookkeeper {@link org.apache.bookkeeper.discover.RegistrationClient}.
   */
  class BKRegistrationNameResolver extends NameResolver {
  
      private final MetadataClientDriver clientDriver;
      private final URI serviceURI;
      private final ScheduledExecutorService executor;
  
      private Listener listener;
      private boolean shutdown;
      private boolean resolving;
      private BookieAddressResolver bookieAddressResolver;
  
      BKRegistrationNameResolver(MetadataClientDriver clientDriver,
                                 URI serviceURI) {
          this.clientDriver = clientDriver;
          this.serviceURI = serviceURI;
          this.executor = Executors.newSingleThreadScheduledExecutor(
              new ThreadFactoryBuilder().setNameFormat("registration-name-resolver").build());
      }
  
      @Override
      public String getServiceAuthority() {
          return serviceURI.getAuthority();
      }
  
      @Override
      public synchronized void start(Listener listener) {
          checkState(null == this.listener, "Resolver already started");
          this.listener = Objects.requireNonNull(listener, "Listener is null");
  
          ClientConfiguration conf = new ClientConfiguration();
          conf.setMetadataServiceUri(serviceURI.toString());
  
          try {
              clientDriver.initialize(conf, executor, NullStatsLogger.INSTANCE, Optional.empty());
          } catch (MetadataException e) {
              throw new RuntimeException("Failed to initialize registration client driver at " + serviceURI, e);
          }
          this.bookieAddressResolver = conf.getBookieAddressResolverEnabled()
                  ? new DefaultBookieAddressResolver(clientDriver.getRegistrationClient())
                  : new BookieAddressResolverDisabled();
  
          resolve();
      }
  
      private synchronized void resolve() {
          if (resolving || shutdown) {
              return;
          }
          resolving = true;
          this.clientDriver.getRegistrationClient().watchWritableBookies(bookies -> {
              Listener savedListener;
              synchronized (this) {
                  savedListener = listener;
              }
              savedListener.onAddresses(
                  hostsToEquivalentAddressGroups(bookies.getValue()),
                  Attributes.EMPTY
              );
          }).whenComplete((ignored, cause) -> {
              try {
                  if (null != cause) {
                      resolve();
                  }
              } finally {
                  synchronized (this) {
                      resolving = false;
                  }
              }
          });
      }
  
      private List<EquivalentAddressGroup> hostsToEquivalentAddressGroups(Set<BookieId> bookies) {
          return bookies.stream()
              .map(addr -> new EquivalentAddressGroup(
                  Collections.singletonList(bookieAddressResolver.resolve(addr).getSocketAddress()),
                  Attributes.EMPTY
              ))
              .collect(Collectors.toList());
      }
  
      @Override
      public void shutdown() {
          synchronized (this) {
              if (shutdown) {
                  return;
              }
              shutdown = true;
          }
          executor.shutdown();
          clientDriver.close();
      }
  }
  