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 com.google.common.collect.Lists;
  import io.grpc.NameResolver;
  import io.grpc.NameResolverProvider;
  import java.net.URI;
  import javax.annotation.Nullable;
  import lombok.extern.slf4j.Slf4j;
  import org.apache.bookkeeper.common.net.ServiceURI;
  import org.apache.bookkeeper.common.resolver.NameResolverFactoryProvider;
  import org.apache.bookkeeper.common.resolver.NameResolverProviderFactory;
  import org.apache.bookkeeper.meta.MetadataClientDriver;
  import org.apache.bookkeeper.meta.MetadataDrivers;
  
  /**
   * An implementation of {@link NameResolverProvider} that provides {@link io.grpc.NameResolver}s
   * to resolve servers registered using bookkeeper registration library.
   */
  @SuppressWarnings("deprecation")
  // One experimental API (ManagedChannelBuilder.nameResolverFactory)
  // is deprecated in favor of another experimental API (NameResolverRegistry).
  // https://github.com/grpc/grpc-java/issues/1770
  // https://github.com/grpc/grpc-java/issues/7133#issuecomment-680981331
  // Skipping the migration for now, will have to deal with this later when GRPC team
  // finalizes their API.
  @Slf4j
  public class BKRegistrationNameResolverProvider extends NameResolverFactoryProvider {
  
      @Override
      protected boolean isAvailable() {
          return true;
      }
  
      @Override
      protected int priority() {
          return 100;
      }
  
      @Nullable
      @Override
      public NameResolver newNameResolver(URI targetUri, NameResolver.Args args) {
          ServiceURI serviceURI;
          try {
              serviceURI = ServiceURI.create(targetUri);
          } catch (NullPointerException | IllegalArgumentException e) {
              // invalid uri here, so return null to allow grpc to use other name resolvers
              log.info("BKRegistrationNameResolverProvider doesn't know how to resolve {} : cause {}",
                  targetUri, e.getMessage());
              return null;
          }
  
          MetadataClientDriver clientDriver;
          try {
              clientDriver = MetadataDrivers.getClientDriver(serviceURI.getUri());
              return new BKRegistrationNameResolver(clientDriver, serviceURI.getUri());
          } catch (IllegalArgumentException iae) {
              log.error("Unknown service uri : {}", serviceURI, iae);
              return null;
          }
      }
  
      @Override
      public String getDefaultScheme() {
          return ServiceURI.SERVICE_ZK;
      }
  
      @Override
      public NameResolver.Factory toFactory() {
          return new NameResolverProviderFactory(Lists.newArrayList(this));
      }
  }
  