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.Endpoints;
  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;
  
  public enum KubernetesEndpoints {
      INSTANCE;
  
      private final LoadingCache<KubernetesEndpoints, List<Endpoints>> endpoints;
  
      @SneakyThrows
      KubernetesEndpoints() {
          final CacheBuilder<Object, Object> cacheBuilder =
                  CacheBuilder.newBuilder()
                          .expireAfterAccess(Duration.ofMinutes(3));
  
          endpoints = cacheBuilder.build(CacheLoader.from(() -> {
              try (final var kubernetesClient = new KubernetesClientBuilder().build()) {
                  return kubernetesClient
                          .endpoints()
                          .inAnyNamespace()
                          .list()
                          .getItems();
              } catch (Exception e) {
                  LoggerFactory.getLogger(getClass()).error("Failed to list Endpoints.", e);
                  return Collections.emptyList();
              }
          }));
      }
  
      @SneakyThrows
      public List<Endpoints> list() {
          return endpoints.get(this);
      }
  }
  