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.istio;
  
  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 com.linecorp.armeria.client.endpoint.dns.DnsAddressEndpointGroup;
  import io.fabric8.istio.api.networking.v1beta1.ServiceEntry;
  import io.fabric8.istio.api.networking.v1beta1.WorkloadEntrySpec;
  import io.fabric8.kubernetes.api.model.ObjectMeta;
  import lombok.SneakyThrows;
  import lombok.extern.slf4j.Slf4j;
  import org.apache.commons.net.util.SubnetUtils;
  import org.apache.skywalking.library.kubernetes.IstioServiceEntries;
  import org.apache.skywalking.oap.server.receiver.envoy.EnvoyMetricReceiverConfig;
  import org.apache.skywalking.oap.server.receiver.envoy.als.ServiceMetaInfo;
  import org.apache.skywalking.oap.server.receiver.envoy.als.k8s.ServiceNameFormatter;
  
  import java.time.Duration;
  import java.util.ArrayList;
  import java.util.List;
  import java.util.Map;
  import java.util.Objects;
  import java.util.concurrent.ConcurrentHashMap;
  import java.util.stream.Collectors;
  
  import static java.util.Objects.isNull;
  
  @Slf4j
  public class IstioServiceEntryRegistry {
      protected final EnvoyMetricReceiverConfig config;
      protected final ServiceNameFormatter serviceNameFormatter;
  
      protected final LoadingCache<String/* ip */, ServiceMetaInfo> ipServiceMetaInfoMap;
      protected final Map<String, DnsAddressEndpointGroup> hostnameResolvers = new ConcurrentHashMap<>();
  
      @SneakyThrows
      public IstioServiceEntryRegistry(final EnvoyMetricReceiverConfig config) {
          this.config = config;
  
          serviceNameFormatter = new ServiceNameFormatter(config.getIstioServiceNameRule());
  
          final var cacheBuilder = CacheBuilder.newBuilder().expireAfterWrite(Duration.ofMinutes(3));
  
          ipServiceMetaInfoMap = cacheBuilder.build(new CacheLoader<>() {
              @Override
              public ServiceMetaInfo load(String ip) {
                  final var serviceEntry = IstioServiceEntries
                      .INSTANCE
                      .list()
                      .parallelStream()
                      .filter(se -> se.getMetadata() != null)
                      .filter(se -> se.getSpec() != null)
                      .filter(se -> {
                          final var spec = se.getSpec();
                          switch (spec.getResolution()) {
                              case STATIC:
                                  return spec
                                      .getAddresses()
                                      .parallelStream()
                                      .anyMatch(address -> {
                                          if (address.contains("/")) { // CIDR
                                              final var subnet = new SubnetUtils(address);
                                              return subnet.getInfo().isInRange(ip);
                                          }
                                          return Objects.equals(ip, address);
                                      }) ||
                                      spec
                                          .getEndpoints()
                                          .parallelStream()
                                          .map(WorkloadEntrySpec::getAddress)
                                          .anyMatch(address -> Objects.equals(address, ip));
                              case DNS:
                              case DNS_ROUND_ROBIN:
                                  return spec
                                      .getHosts()
                                      .parallelStream()
                                      .map(host -> hostnameResolvers.computeIfAbsent(host, it -> {
                                          final var endpointGroup = DnsAddressEndpointGroup.of(it);
                                          endpointGroup.whenReady().join(); // Wait for the first resolution
                                          return endpointGroup;
                                      }))
                                      .anyMatch(dnsAddressEndpointGroup ->
                                          dnsAddressEndpointGroup
                                              .endpoints()
                                              .parallelStream()
                                              .anyMatch(endpoint -> Objects.equals(endpoint.ipAddr(), ip)));
                              default:
                                  log.debug("Unsupported service entry resolution: {}", spec.getResolution());
                                  return false;
                          }
                      })
                      .findFirst();
  
                  if (serviceEntry.isEmpty()) {
                      log.debug("No corresponding service entry for IP: {}", ip);
                      return config.serviceMetaInfoFactory().unknown();
                  }
  
                  log.debug(
                      "Composing service meta info from service entry for IP: {}", ip);
                  return composeServiceMetaInfo(serviceEntry.get(), ip);
              }
          });
      }
  
      protected List<ServiceMetaInfo.KeyValue> transformLabelsToTags(final ObjectMeta serviceEntryMeta) {
          final var labels = serviceEntryMeta.getLabels();
          final var tags = new ArrayList<ServiceMetaInfo.KeyValue>();
          tags.add(new ServiceMetaInfo.KeyValue("namespace", serviceEntryMeta.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) {
          return ipServiceMetaInfoMap.get(ip);
      }
  
      protected ServiceMetaInfo composeServiceMetaInfo(final ServiceEntry serviceEntry, String ip) {
          final var context = ImmutableMap.<String, Object>of("serviceEntry", serviceEntry);
          final var serviceMetaInfo = new ServiceMetaInfo();
  
          try {
              serviceMetaInfo.setServiceName(serviceNameFormatter.format(context));
          } catch (Exception e) {
              log.error("Failed to evaluate serviceEntry name.", e);
              final var serviceMetadata = serviceEntry.getMetadata();
              if (isNull(serviceMetadata)) {
                  log.warn("Service metadata is null, {}", serviceEntry);
                  return config.serviceMetaInfoFactory().unknown();
              }
              serviceMetaInfo.setServiceName(serviceMetadata.getName());
          }
          serviceMetaInfo.setTags(transformLabelsToTags(serviceEntry.getMetadata()));
          serviceMetaInfo.setServiceInstanceName(ip);
  
          return serviceMetaInfo;
      }
  }
  