content: /*
   * Copyright 1999-2018 Alibaba Group Holding Ltd.
   *
   * Licensed 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 com.alibaba.nacos.naming.core;
  
  import com.alibaba.nacos.common.notify.NotifyCenter;
  import com.alibaba.nacos.core.cluster.MemberChangeListener;
  import com.alibaba.nacos.core.cluster.MemberUtil;
  import com.alibaba.nacos.core.cluster.MembersChangeEvent;
  import com.alibaba.nacos.api.common.NodeState;
  import com.alibaba.nacos.core.cluster.ServerMemberManager;
  import com.alibaba.nacos.naming.misc.Loggers;
  import com.alibaba.nacos.naming.misc.SwitchDomain;
  import com.alibaba.nacos.sys.env.EnvUtil;
  import org.apache.commons.collections.CollectionUtils;
  import org.springframework.stereotype.Component;
  
  import javax.annotation.PostConstruct;
  import java.util.ArrayList;
  import java.util.Collection;
  import java.util.Collections;
  import java.util.List;
  
  /**
   * Distro mapper, judge which server response input service.
   *
   * @author nkorange
   */
  @Component("distroMapper")
  public class DistroMapper extends MemberChangeListener {
      
      /**
       * List of service nodes, you must ensure that the order of healthyList is the same for all nodes.
       */
      private volatile List<String> healthyList = new ArrayList<>();
      
      private final SwitchDomain switchDomain;
      
      private final ServerMemberManager memberManager;
      
      public DistroMapper(ServerMemberManager memberManager, SwitchDomain switchDomain) {
          this.memberManager = memberManager;
          this.switchDomain = switchDomain;
      }
      
      public List<String> getHealthyList() {
          return healthyList;
      }
      
      /**
       * init server list.
       */
      @PostConstruct
      public void init() {
          NotifyCenter.registerSubscriber(this);
          this.healthyList = MemberUtil.simpleMembers(memberManager.allMembers());
      }
      
      /**
       * Judge whether current server is responsible for input tag.
       *
       * @param responsibleTag responsible tag, serviceName for v1 and ip:port for v2
       * @return true if input service is response, otherwise false
       */
      public boolean responsible(String responsibleTag) {
          final List<String> servers = healthyList;
          
          if (!switchDomain.isDistroEnabled() || EnvUtil.getStandaloneMode()) {
              return true;
          }
          
          if (CollectionUtils.isEmpty(servers)) {
              // means distro config is not ready yet
              return false;
          }
          
          String localAddress = EnvUtil.getLocalAddress();
          int index = servers.indexOf(localAddress);
          int lastIndex = servers.lastIndexOf(localAddress);
          if (lastIndex < 0 || index < 0) {
              return true;
          }
          
          int target = distroHash(responsibleTag) % servers.size();
          return target >= index && target <= lastIndex;
      }
      
      /**
       * Calculate which other server response input tag.
       *
       * @param responsibleTag responsible tag, serviceName for v1 and ip:port for v2
       * @return server which response input service
       */
      public String mapSrv(String responsibleTag) {
          final List<String> servers = healthyList;
          
          if (CollectionUtils.isEmpty(servers) || !switchDomain.isDistroEnabled()) {
              return EnvUtil.getLocalAddress();
          }
          
          try {
              int index = distroHash(responsibleTag) % servers.size();
              return servers.get(index);
          } catch (Throwable e) {
              Loggers.SRV_LOG
                      .warn("[NACOS-DISTRO] distro mapper failed, return localhost: " + EnvUtil.getLocalAddress(), e);
              return EnvUtil.getLocalAddress();
          }
      }
      
      private int distroHash(String responsibleTag) {
          return Math.abs(responsibleTag.hashCode() % Integer.MAX_VALUE);
      }
      
      @Override
      public void onEvent(MembersChangeEvent event) {
          // Here, the node list must be sorted to ensure that all nacos-server's
          // node list is in the same order
          List<String> list = MemberUtil.simpleMembers(MemberUtil.selectTargetMembers(event.getMembers(),
                  member -> NodeState.UP.equals(member.getState()) || NodeState.SUSPICIOUS.equals(member.getState())));
          Collections.sort(list);
          Collection<String> old = healthyList;
          healthyList = Collections.unmodifiableList(list);
          Loggers.SRV_LOG.info("[NACOS-DISTRO] healthy server list changed, old: {}, new: {}", old, healthyList);
      }
      
      @Override
      public boolean ignoreExpireEvent() {
          return true;
      }
  }
  