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.common.executor;
  
  import com.alibaba.nacos.common.JustForTest;
  import com.alibaba.nacos.common.utils.ThreadUtils;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  import java.util.HashMap;
  import java.util.HashSet;
  import java.util.Map;
  import java.util.Set;
  import java.util.concurrent.ConcurrentHashMap;
  import java.util.concurrent.ExecutorService;
  import java.util.concurrent.atomic.AtomicBoolean;
  
  /**
   * // TODO Access Metric.
   *
   * <p>For unified management of thread pool resources, the consumer can simply call the register method to {@link
   * ThreadPoolManager#register(String, String, ExecutorService)} the thread pool that needs to be included in the life
   * cycle management of the resource
   *
   * @author <a href="mailto:liaochuntao@live.com">liaochuntao</a>
   */
  public final class ThreadPoolManager {
      
      private static final Logger LOGGER = LoggerFactory.getLogger(ThreadPoolManager.class);
      
      private Map<String, Map<String, Set<ExecutorService>>> resourcesManager;
      
      private static final ThreadPoolManager INSTANCE = new ThreadPoolManager();
      
      private static final AtomicBoolean CLOSED = new AtomicBoolean(false);
      
      static {
          INSTANCE.init();
          ThreadUtils.addShutdownHook(new Thread(() -> {
              LOGGER.info("[ThreadPoolManager] Start destroying ThreadPool");
              shutdown();
              LOGGER.info("[ThreadPoolManager] Completed destruction of ThreadPool");
          }));
      }
      
      public static ThreadPoolManager getInstance() {
          return INSTANCE;
      }
      
      private ThreadPoolManager() {
      }
      
      private void init() {
          resourcesManager = new ConcurrentHashMap<>(8);
      }
      
      /**
       * Register the thread pool resources with the resource manager.
       *
       * @param namespace namespace name
       * @param group     group name
       * @param executor  {@link ExecutorService}
       */
      public void register(String namespace, String group, ExecutorService executor) {
          resourcesManager.compute(namespace, (namespaceKey, map) -> {
              if (map == null) {
                  map = new HashMap<>(8);
              }
              map.computeIfAbsent(group, groupKey -> new HashSet<>()).add(executor);
              return map;
          });
      }
      
      /**
       * Cancel the uniform lifecycle management for all threads under this resource.
       *
       * @param namespace namespace name
       * @param group     group name
       */
      public void deregister(String namespace, String group) {
          resourcesManager.computeIfPresent(namespace, (key, map) -> {
              map.remove(group);
              return map;
          });
      }
      
      /**
       * Undoing the uniform lifecycle management of {@link ExecutorService} under this resource.
       *
       * @param namespace namespace name
       * @param group     group name
       * @param executor  {@link ExecutorService}
       */
      public void deregister(String namespace, String group, ExecutorService executor) {
          resourcesManager.computeIfPresent(namespace, (namespaceKey, map) -> {
              map.computeIfPresent(group, (groupKey, set) -> {
                  set.remove(executor);
                  return set;
              });
              return map;
          });
      }
      
      /**
       * Destroys all thread pool resources under this namespace.
       *
       * @param namespace namespace
       */
      public void destroy(final String namespace) {
          Map<String, Set<ExecutorService>> map = resourcesManager.remove(namespace);
          if (map != null) {
              for (Set<ExecutorService> set : map.values()) {
                  for (ExecutorService executor : set) {
                      ThreadUtils.shutdownThreadPool(executor);
                  }
                  set.clear();
              }
              map.clear();
          }
      }
      
      /**
       * This namespace destroys all thread pool resources under the grouping.
       *
       * @param namespace namespace
       * @param group     group
       */
      public void destroy(final String namespace, final String group) {
          resourcesManager.computeIfPresent(namespace, (namespaceKey, map) -> {
              map.computeIfPresent(group, (groupKey, set) -> {
                  for (ExecutorService executor : set) {
                      ThreadUtils.shutdownThreadPool(executor);
                  }
                  set.clear();
                  return null;
              });
              return map;
          });
      }
      
      /**
       * Shutdown thread pool manager.
       */
      public static void shutdown() {
          if (!CLOSED.compareAndSet(false, true)) {
              return;
          }
          Set<String> namespaces = INSTANCE.resourcesManager.keySet();
          for (String namespace : namespaces) {
              INSTANCE.destroy(namespace);
          }
      }
      
      @JustForTest
      public Map<String, Map<String, Set<ExecutorService>>> getResourcesManager() {
          return resourcesManager;
      }
  }
  