code: /*
   * 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.skywalking.oap.server.configuration.grpc;
  
  import io.grpc.netty.NettyChannelBuilder;
  import java.util.Objects;
  import java.util.Optional;
  import java.util.Set;
  import lombok.extern.slf4j.Slf4j;
  import org.apache.skywalking.oap.server.configuration.api.ConfigTable;
  import org.apache.skywalking.oap.server.configuration.api.ConfigWatcherRegister;
  import org.apache.skywalking.oap.server.configuration.api.GroupConfigTable;
  import org.apache.skywalking.oap.server.configuration.service.ConfigurationRequest;
  import org.apache.skywalking.oap.server.configuration.service.ConfigurationResponse;
  import org.apache.skywalking.oap.server.configuration.service.ConfigurationServiceGrpc;
  import org.apache.skywalking.oap.server.configuration.service.GroupConfigurationResponse;
  
  @Slf4j
  public class GRPCConfigWatcherRegister extends ConfigWatcherRegister {
      private RemoteEndpointSettings settings;
      private ConfigurationServiceGrpc.ConfigurationServiceBlockingStub stub;
      private String uuid = null;
      private String groupUuid = null;
  
      public GRPCConfigWatcherRegister(RemoteEndpointSettings settings) {
          super(settings.getPeriod());
          this.settings = settings;
          stub = ConfigurationServiceGrpc.newBlockingStub(
              NettyChannelBuilder.forAddress(settings.getHost(), settings.getPort())
                                 .usePlaintext()
                                 .build());
      }
  
      @Override
      public Optional<ConfigTable> readConfig(Set<String> keys) {
          ConfigTable table = new ConfigTable();
          try {
              ConfigurationRequest.Builder builder = ConfigurationRequest.newBuilder()
                                                                         .setClusterName(settings.getClusterName());
              if (uuid != null) {
                  builder.setUuid(uuid);
              }
              ConfigurationResponse response = stub.call(builder.build());
              String responseUuid = response.getUuid();
              if (Objects.equals(uuid, responseUuid)) {
                  // If UUID matched, the config table is expected as empty.
                  return Optional.empty();
              }
              response.getConfigTableList().forEach(config -> {
                  final String name = config.getName();
                  if (keys.contains(name)) {
                      table.add(new ConfigTable.ConfigItem(name, config.getValue()));
                  }
              });
              this.uuid = responseUuid;
          } catch (Exception e) {
              log.error("Remote config center [{}] is not available.", settings, e);
          }
          return Optional.of(table);
      }
  
      @Override
      public Optional<GroupConfigTable> readGroupConfig(final Set<String> keys) {
          GroupConfigTable groupConfigTable = new GroupConfigTable();
          try {
              ConfigurationRequest.Builder builder = ConfigurationRequest.newBuilder()
                                                                         .setClusterName(settings.getClusterName());
              if (groupUuid != null) {
                  builder.setUuid(groupUuid);
              }
              GroupConfigurationResponse response = stub.callGroup(builder.build());
              String responseUuid = response.getUuid();
              if (Objects.equals(groupUuid, responseUuid)) {
                  // If UUID matched, the config table is expected as empty.
                  return Optional.empty();
              }
  
              response.getGroupConfigTableList().forEach(rspGroupConfigItems -> {
                  String groupName = rspGroupConfigItems.getGroupName();
                  if (keys.contains(groupName)) {
                      GroupConfigTable.GroupConfigItems groupConfigItems = new GroupConfigTable.GroupConfigItems(
                          groupName);
                      groupConfigTable.addGroupConfigItems(groupConfigItems);
                      rspGroupConfigItems.getItemsList().forEach(item -> {
                          groupConfigItems.add(new ConfigTable.ConfigItem(item.getName(), item.getValue()));
                      });
                  }
              });
              this.groupUuid = responseUuid;
          } catch (Exception e) {
              log.error("Remote config center [{}] is not available.", settings, e);
          }
          return Optional.of(groupConfigTable);
      }
  }
  