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.zookeeper;
  
  import java.nio.charset.StandardCharsets;
  import java.util.Optional;
  import java.util.Set;
  import lombok.extern.slf4j.Slf4j;
  import org.apache.curator.RetryPolicy;
  import org.apache.curator.framework.CuratorFramework;
  import org.apache.curator.framework.CuratorFrameworkFactory;
  import org.apache.curator.framework.recipes.cache.ChildData;
  import org.apache.curator.framework.recipes.cache.PathChildrenCache;
  import org.apache.curator.retry.ExponentialBackoffRetry;
  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;
  
  @Slf4j
  public class ZookeeperConfigWatcherRegister extends ConfigWatcherRegister {
      private final CuratorFramework client;
      private final PathChildrenCache childrenCache;
      private final String prefix;
  
      public ZookeeperConfigWatcherRegister(ZookeeperServerSettings settings) throws Exception {
          super(settings.getPeriod());
          prefix = settings.getNamespace() + "/";
          RetryPolicy retryPolicy = new ExponentialBackoffRetry(settings.getBaseSleepTimeMs(), settings.getMaxRetries());
          this.client = CuratorFrameworkFactory.newClient(settings.getHostPort(), retryPolicy);
          client.start();
          this.childrenCache = new PathChildrenCache(client, settings.getNamespace(), true);
          this.childrenCache.start();
      }
  
      @Override
      public Optional<ConfigTable> readConfig(Set<String> keys) {
          ConfigTable table = new ConfigTable();
          keys.forEach(s -> {
              ChildData data = this.childrenCache.getCurrentData(this.prefix + s);
              String itemValue = null;
              if (data != null && data.getData() != null) {
                  itemValue = new String(data.getData(), StandardCharsets.UTF_8);
              }
              table.add(new ConfigTable.ConfigItem(s, itemValue));
          });
          return Optional.of(table);
      }
  
      @Override
      public Optional<GroupConfigTable> readGroupConfig(final Set<String> keys) {
          GroupConfigTable table = new GroupConfigTable();
          keys.forEach(key -> {
              GroupConfigTable.GroupConfigItems groupConfigItems = new GroupConfigTable.GroupConfigItems(key);
              try {
                  client.getChildren().forPath(this.prefix + key).forEach(itemName -> {
                      byte[] data = null;
                      try {
                          data = client.getData().forPath(this.prefix + key + "/" + itemName);
                      } catch (Exception e) {
                          log.error(e.getMessage(), e);
                      }
                      groupConfigItems.add(
                          new ConfigTable.ConfigItem(
                              itemName, data == null ? null : new String(data, StandardCharsets.UTF_8)));
                  });
              } catch (Exception e) {
                  log.error(e.getMessage(), e);
              }
              table.addGroupConfigItems(groupConfigItems);
          });
          return Optional.of(table);
      }
  }
  