content: /**
   * 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.hive.service.server;
  
  import java.util.Map;
  import java.util.concurrent.ConcurrentHashMap;
  import java.util.concurrent.ThreadFactory;
  
  import org.apache.hadoop.hive.metastore.RawStore;
  
  /**
   * A ThreadFactory for constructing new HiveServer2 threads that lets you plug
   * in custom cleanup code to be called before this thread is GC-ed.
   * Currently cleans up the following:
   * 1. ThreadLocal RawStore object:
   * In case of an embedded metastore, HiveServer2 threads (foreground & background)
   * end up caching a ThreadLocal RawStore object. The ThreadLocal RawStore object has
   * an instance of PersistenceManagerFactory & PersistenceManager.
   * The PersistenceManagerFactory keeps a cache of PersistenceManager objects,
   * which are only removed when PersistenceManager#close method is called.
   * HiveServer2 uses ExecutorService for managing thread pools for foreground & background threads.
   * ExecutorService unfortunately does not provide any hooks to be called,
   * when a thread from the pool is terminated.
   * As a solution, we're using this ThreadFactory to keep a cache of RawStore objects per thread.
   * And we are doing clean shutdown in the finalizer for each thread.
   */
  public class ThreadFactoryWithGarbageCleanup implements ThreadFactory {
  
    private static Map<Long, RawStore> threadRawStoreMap = new ConcurrentHashMap<Long, RawStore>();
  
    private final String namePrefix;
  
    public ThreadFactoryWithGarbageCleanup(String threadPoolName) {
      namePrefix = threadPoolName;
    }
  
    @Override
    public Thread newThread(Runnable runnable) {
      Thread newThread = new ThreadWithGarbageCleanup(runnable);
      newThread.setName(namePrefix + ": Thread-" + newThread.getId());
      return newThread;
    }
  
    public static Map<Long, RawStore> getThreadRawStoreMap() {
      return threadRawStoreMap;
    }
  }
  