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.cassandra.utils.concurrent;
  
  import java.util.ArrayList;
  import java.util.List;
  import java.util.Map;
  import java.util.NavigableMap;
  import java.util.Random;
  import java.util.concurrent.ConcurrentSkipListMap;
  import java.util.concurrent.TimeUnit;
  import java.util.concurrent.atomic.AtomicBoolean;
  import java.util.concurrent.atomic.AtomicLong;
  import java.util.concurrent.locks.LockSupport;
  
  import org.junit.Test;
  
  import org.apache.cassandra.concurrent.ExecutorPlus;
  import org.apache.cassandra.utils.EstimatedHistogram;
  import org.apache.cassandra.utils.FBUtilities;
  
  import static java.util.concurrent.TimeUnit.NANOSECONDS;
  import static org.apache.cassandra.concurrent.ExecutorFactory.Global.executorFactory;
  
  public class LockWithAsyncSignalTest
  {
      @Test
      public void test()
      {
          ExecutorPlus submitters = executorFactory().pooled("test-submitters", 16);
          ExecutorPlus consumers = executorFactory().pooled("test-consumers", 16);
          for (int i = 0 ; i < 10 ; ++i)
              testOne(submitters, consumers, 4, 8, i);
      }
  
      private static void testOne(ExecutorPlus submitterExecutor, ExecutorPlus consumerExecutor, int submitterCount, int consumerCount, int seconds)
      {
          class Waiting extends AtomicBoolean implements Comparable<Waiting>
          {
              final long ticket;
  
              Waiting(long ticket)
              {
                  this.ticket = ticket;
              }
  
              @Override
              public int compareTo(Waiting that)
              {
                  return Long.compare(this.ticket, that.ticket);
              }
          }
          final LockWithAsyncSignal lock = new LockWithAsyncSignal();
          final List<Future<Object>> submitters = new ArrayList<>();
          final List<Future<Object>> consumers = new ArrayList<>();
          final AtomicBoolean submittersRunning = new AtomicBoolean(true);
          final AtomicBoolean consumersRunning = new AtomicBoolean(true);
          final ConcurrentSkipListMap<Waiting, Boolean> waiting = new ConcurrentSkipListMap<>();
          final AtomicLong nextTicket = new AtomicLong();
          final EstimatedHistogram latency = new EstimatedHistogram();
          for (int i = 0; i < submitterCount + consumerCount ; ++i)
          {
              boolean submitter = i/2 >= consumerCount || ((i & 1) == 0 && i/2 < submitterCount);
              if (submitter)
              {
                  submitters.add(submitterExecutor.submit(() -> {
                      final Random rnd = new Random();
                      while (submittersRunning.get())
                      {
                          LockSupport.parkNanos(TimeUnit.MICROSECONDS.toNanos(rnd.nextInt(100)));
                          long start = System.nanoTime();
                          Waiting awaiting = new Waiting(nextTicket.incrementAndGet());
                          waiting.put(awaiting, true);
                          lock.signal();
                          while (!awaiting.get());
                          long end = System.nanoTime();
                          latency.add(NANOSECONDS.toMicros(end - start));
                      }
                      return null;
                  }));
              }
              else
              {
                  consumers.add(consumerExecutor.submit(() -> {
                      final Random rnd = new Random();
                      while (true)
                      {
                          if (rnd.nextBoolean()) lock.lock();
                          else if (!lock.tryLock()) continue;
  
                          Waiting waitUntil;
                          try
                          {
                              AtomicBoolean awaiting;
                              while (null != (awaiting = pollFirst(waiting)))
                                  awaiting.set(true);
  
                              lock.await();
                              if (null != (awaiting = pollFirst(waiting)))
                                  awaiting.set(true);
  
                              if (!consumersRunning.get())
                              {
                                  lock.signal();
                                  return null;
                              }
  
                              waitUntil = peekLast(waiting);
                              if (!waiting.isEmpty())
                                  lock.signal();
                          }
                          finally
                          {
                              lock.unlock();
                          }
  
                          if (waitUntil != null)
                          {
                              while (!waitUntil.get());
                          }
                      }
                  }));
              }
          }
          long deadline = System.nanoTime() + TimeUnit.SECONDS.toNanos(seconds);
          while (true)
          {
              long wait = deadline - System.nanoTime();
              if (wait < 0)
                  break;
              LockSupport.parkNanos(wait);
          }
          submittersRunning.set(false);
          lock.signal();
          FBUtilities.waitOnFutures(submitters, 2L, TimeUnit.SECONDS);
          consumersRunning.set(false);
          FBUtilities.waitOnFutures(consumers, 2L, TimeUnit.SECONDS);
      }
  
      private static <T> T pollFirst(NavigableMap<T, ?> map)
      {
          Map.Entry<T, ?> e = map.pollFirstEntry();
          return e == null ? null : e.getKey();
      }
  
      private static <T> T peekLast(NavigableMap<T, ?> map)
      {
          Map.Entry<T, ?> e = map.lastEntry();
          return e == null ? null : e.getKey();
      }
  }
  