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.core.cluster;
  
  import com.google.common.collect.Sets;
  import lombok.Setter;
  import org.apache.skywalking.oap.server.core.CoreModuleConfig;
  import org.apache.skywalking.oap.server.library.util.CollectionUtils;
  
  import java.util.List;
  import java.util.Set;
  import java.util.stream.Collectors;
  
  public class OAPNodeChecker {
      private static final Set<String> ILLEGAL_NODE_ADDRESS_IN_CLUSTER_MODE = Sets.newHashSet("127.0.0.1", "localhost");
  
      @Setter
      private static CoreModuleConfig.Role ROLE = CoreModuleConfig.Role.Mixed;
  
      public static boolean hasIllegalNodeAddress(List<RemoteInstance> remoteInstances) {
          if (CollectionUtils.isEmpty(remoteInstances)) {
              return false;
          }
          Set<String> remoteAddressSet = remoteInstances.stream().map(remoteInstance ->
                  remoteInstance.getAddress().getHost()).collect(Collectors.toSet());
          return !Sets.intersection(ILLEGAL_NODE_ADDRESS_IN_CLUSTER_MODE, remoteAddressSet).isEmpty();
      }
  
      /**
       * Check the remote instance healthiness, set health to false for bellow conditions:
       * 1.can't get the instance list
       * 2.can't get itself
       * 3.check for illegal node in cluster mode such as 127.0.0.1, localhost
       *
       * @param remoteInstances all the remote instances from cluster
       * @return true health false unHealth
       */
      public static ClusterHealthStatus isHealth(List<RemoteInstance> remoteInstances) {
          if (CollectionUtils.isEmpty(remoteInstances)) {
              return ClusterHealthStatus.unHealth("can't get the instance list");
          }
          if (!CoreModuleConfig.Role.Receiver.equals(ROLE)) {
              List<RemoteInstance> selfInstances = remoteInstances.stream().
                      filter(remoteInstance -> remoteInstance.getAddress().isSelf()).collect(Collectors.toList());
              if (CollectionUtils.isEmpty(selfInstances)) {
                  return ClusterHealthStatus.unHealth("can't get itself");
              }
          }
          if (remoteInstances.size() > 1 && hasIllegalNodeAddress(remoteInstances)) {
              return ClusterHealthStatus.unHealth("find illegal node in cluster mode such as 127.0.0.1, localhost");
          }
          return ClusterHealthStatus.HEALTH;
      }
  }