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.receiver.envoy.als.k8s;
  
  import com.google.common.cache.CacheBuilder;
  import com.google.common.cache.CacheLoader;
  import com.google.common.cache.LoadingCache;
  import com.google.common.collect.ImmutableMap;
  import io.fabric8.kubernetes.api.model.Node;
  import io.fabric8.kubernetes.api.model.NodeAddress;
  import io.fabric8.kubernetes.api.model.NodeStatus;
  import io.fabric8.kubernetes.api.model.ObjectMeta;
  import io.fabric8.kubernetes.api.model.Pod;
  import io.fabric8.kubernetes.api.model.Service;
  import io.fabric8.kubernetes.client.KubernetesClientBuilder;
  import lombok.SneakyThrows;
  import lombok.extern.slf4j.Slf4j;
  import org.apache.skywalking.library.kubernetes.KubernetesEndpoints;
  import org.apache.skywalking.library.kubernetes.KubernetesPods;
  import org.apache.skywalking.library.kubernetes.KubernetesServices;
  import org.apache.skywalking.library.kubernetes.ObjectID;
  import org.apache.skywalking.oap.server.library.util.StringUtil;
  import org.apache.skywalking.oap.server.receiver.envoy.EnvoyMetricReceiverConfig;
  import org.apache.skywalking.oap.server.receiver.envoy.als.ServiceMetaInfo;
  
  import java.time.Duration;
  import java.util.ArrayList;
  import java.util.Collections;
  import java.util.List;
  import java.util.Map;
  import java.util.Objects;
  import java.util.Optional;
  import java.util.Set;
  import java.util.stream.Collectors;
  
  import static java.util.Objects.isNull;
  import static java.util.stream.Collectors.toSet;
  
  @Slf4j
  public class K8SServiceRegistry {
      protected final EnvoyMetricReceiverConfig config;
      protected final ServiceNameFormatter serviceNameFormatter;
  
      protected final LoadingCache<K8SServiceRegistry, Set<String>> nodeIPs;
      protected final LoadingCache<String/* ip */, ServiceMetaInfo> ipServiceMetaInfoMap;
  
      @SneakyThrows
      public K8SServiceRegistry(final EnvoyMetricReceiverConfig config) {
          this.config = config;
  
          serviceNameFormatter = new ServiceNameFormatter(config.getK8sServiceNameRule());
  
          final CacheBuilder<Object, Object> cacheBuilder =
              CacheBuilder.newBuilder()
                  .expireAfterWrite(Duration.ofMinutes(3));
  
          nodeIPs = cacheBuilder.build(CacheLoader.from(() -> {
              try (final var kubernetesClient = new KubernetesClientBuilder().build()) {
                  return kubernetesClient
                      .nodes()
                      .list()
                      .getItems()
                      .stream()
                      .map(Node::getStatus)
                      .map(NodeStatus::getAddresses)
                      .flatMap(it -> it.stream().map(NodeAddress::getAddress)
                          .filter(StringUtil::isNotBlank))
                      .collect(toSet());
              } catch (Exception e) {
                  log.error("Failed to list Nodes.", e);
                  return Collections.emptySet();
              }
          }));
  
          ipServiceMetaInfoMap = cacheBuilder.build(new CacheLoader<>() {
              @Override
              public ServiceMetaInfo load(String ip) {
                  final Optional<Pod> pod = KubernetesPods.INSTANCE.findByIP(ip);
                  if (pod.isEmpty()) {
                      log.debug("No corresponding Pod for IP: {}", ip);
                      return config.serviceMetaInfoFactory().unknown();
                  }
  
                  final Optional<ObjectID> serviceID =
                      KubernetesEndpoints.INSTANCE
                          .list()
                          .stream()
                          .filter(endpoints -> endpoints.getMetadata() != null)
                          .filter(endpoints -> endpoints.getSubsets() != null)
                          .map(endpoints -> {
                              final ObjectMeta metadata = endpoints.getMetadata();
                              if (endpoints
                                  .getSubsets()
                                  .stream()
                                  .filter(subset -> subset.getAddresses() != null)
                                  .flatMap(subset -> subset.getAddresses().stream())
                                  .anyMatch(address -> Objects.equals(ip, address.getIp()))) {
                                  return ObjectID
                                      .builder()
                                      .name(metadata.getName())
                                      .namespace(metadata.getNamespace())
                                      .build();
                              }
                              return null;
                          })
                          .filter(Objects::nonNull)
                          .findFirst();
                  if (serviceID.isEmpty()) {
                      log.debug("No corresponding endpoint for IP: {}", ip);
                      return config.serviceMetaInfoFactory().unknown();
                  }
  
                  final Optional<Service> service =
                      KubernetesServices.INSTANCE.findByID(serviceID.get());
                  if (service.isEmpty()) {
                      log.debug("No service for namespace and name: {}", serviceID.get());
                      return config.serviceMetaInfoFactory().unknown();
                  }
                  log.debug(
                      "Composing service meta info from service and pod for IP: {}", ip);
                  return composeServiceMetaInfo(service.get(), pod.get());
              }
          });
      }
  
      protected List<ServiceMetaInfo.KeyValue> transformLabelsToTags(final ObjectMeta podMeta) {
          final Map<String, String> labels = podMeta.getLabels();
          final List<ServiceMetaInfo.KeyValue> tags = new ArrayList<>();
          tags.add(new ServiceMetaInfo.KeyValue("pod", podMeta.getName()));
          tags.add(new ServiceMetaInfo.KeyValue("namespace", podMeta.getNamespace()));
          if (isNull(labels)) {
              return tags;
          }
          return labels.entrySet()
              .stream()
              .map(each -> new ServiceMetaInfo.KeyValue(each.getKey(), each.getValue()))
              .collect(Collectors.toCollection(() -> tags));
      }
  
      @SneakyThrows
      public ServiceMetaInfo findService(final String ip) {
          if (isNode(ip)) {
              return config.serviceMetaInfoFactory().unknown();
          }
          return ipServiceMetaInfoMap.get(ip);
      }
  
      protected ServiceMetaInfo composeServiceMetaInfo(final Service service, final Pod pod) {
          final Map<String, Object> context = ImmutableMap.of("service", service, "pod", pod);
          final ServiceMetaInfo serviceMetaInfo = new ServiceMetaInfo();
          final ObjectMeta podMetadata = pod.getMetadata();
  
          try {
              serviceMetaInfo.setServiceName(serviceNameFormatter.format(context));
          } catch (Exception e) {
              log.error("Failed to evaluate service name.", e);
              final ObjectMeta serviceMetadata = service.getMetadata();
              if (isNull(serviceMetadata)) {
                  log.warn("Service metadata is null, {}", service);
                  return config.serviceMetaInfoFactory().unknown();
              }
              serviceMetaInfo.setServiceName(serviceMetadata.getName());
          }
          serviceMetaInfo.setServiceInstanceName(
              String.format("%s.%s", podMetadata.getName(), podMetadata.getNamespace()));
          serviceMetaInfo.setTags(transformLabelsToTags(podMetadata));
  
          return serviceMetaInfo;
      }
  
      @SneakyThrows
      public boolean isNode(final String ip) {
          return nodeIPs.get(this).contains(ip);
      }
  }
  