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.asterix.transaction.management.service.locking;
  
  import static org.apache.asterix.transaction.management.service.locking.ConcurrentLockManager.NILL;
  
  import java.util.concurrent.TimeUnit;
  import java.util.concurrent.locks.Condition;
  import java.util.concurrent.locks.ReentrantLock;
  
  import org.apache.asterix.common.transactions.ITransactionContext;
  
  /**
   * A ResourceGroup represents a group of resources that are manged by a ConcurrentLockManager.
   * All resources in a group share a common latch. I.e. all modifications of lock requests for any resource in a group
   * are protected by the same latch.
   *
   * @see ConcurrentLockManager
   */
  class ResourceGroup {
      private final ReentrantLock latch;
      private final Condition condition;
      volatile long firstResourceIndex;
  
      ResourceGroup() {
          latch = new ReentrantLock();
          condition = latch.newCondition();
          firstResourceIndex = NILL;
      }
  
      void getLatch() {
          log("latch");
          latch.lock();
      }
  
      boolean tryLatch(long timeout, TimeUnit unit) throws InterruptedException {
          log("tryLatch");
          try {
              return latch.tryLock(timeout, unit);
          } catch (InterruptedException e) {
              ConcurrentLockManager.LOGGER.trace("interrupted while wating on ResourceGroup");
              throw e;
          }
      }
  
      void releaseLatch() {
          log("release");
          latch.unlock();
      }
  
      boolean hasWaiters() {
          return latch.hasQueuedThreads();
      }
  
      void await(ITransactionContext txnContext) throws InterruptedException {
          log("wait for");
          try {
              condition.await();
          } catch (InterruptedException e) {
              ConcurrentLockManager.LOGGER.trace("interrupted while waiting on ResourceGroup");
              throw e;
          }
      }
  
      void wakeUp() {
          log("notify");
          condition.signalAll();
      }
  
      void log(String s) {
          if (ConcurrentLockManager.LOGGER.isEnabled(ConcurrentLockManager.LVL)) {
              ConcurrentLockManager.LOGGER.log(ConcurrentLockManager.LVL, s + " " + toString());
          }
      }
  
      public String toString() {
          return "{ id : " + hashCode() + ", first : " + TypeUtil.Global.toString(firstResourceIndex) + ", "
                  + "waiters : " + (hasWaiters() ? "true" : "false") + " }";
      }
  }
  