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.library.kubernetes;
  
  import com.google.common.cache.CacheBuilder;
  import com.google.common.cache.CacheLoader;
  import com.google.common.cache.LoadingCache;
  import io.fabric8.kubernetes.api.model.Service;
  import io.fabric8.kubernetes.client.KubernetesClientBuilder;
  import lombok.SneakyThrows;
  import org.slf4j.LoggerFactory;
  
  import java.time.Duration;
  import java.util.Collections;
  import java.util.List;
  import java.util.Optional;
  
  public enum KubernetesServices {
      INSTANCE;
  
      private final LoadingCache<KubernetesServices, List<Service>> services;
      private final LoadingCache<ObjectID, Optional<Service>> serviceByID;
  
      @SneakyThrows
      KubernetesServices() {
          final CacheBuilder<Object, Object> cacheBuilder =
                  CacheBuilder.newBuilder()
                          .expireAfterAccess(Duration.ofMinutes(3));
  
          services = cacheBuilder.build(CacheLoader.from(() -> {
              try (final var kubernetesClient = new KubernetesClientBuilder().build()) {
                  return kubernetesClient
                          .services()
                          .inAnyNamespace()
                          .list()
                          .getItems();
              } catch (Exception e) {
                  LoggerFactory.getLogger(getClass()).error("Failed to list Services.", e);
                  return Collections.emptyList();
              }
          }));
  
          serviceByID = cacheBuilder.build(new CacheLoader<>() {
              @Override
              public Optional<Service> load(ObjectID id) {
                  try (final var kubernetesClient = new KubernetesClientBuilder().build()) {
                      return Optional.ofNullable(
                          kubernetesClient
                              .services()
                              .inNamespace(id.namespace())
                              .withName(id.name())
                              .get());
                  }
              }
          });
      }
  
      @SneakyThrows
      public List<Service> list() {
          return services.get(this);
      }
  
      @SneakyThrows
      public Optional<Service> findByID(final ObjectID id) {
          return serviceByID.get(id);
      }
  }
  