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.beam.runners.dataflow.worker;
  
  import static org.hamcrest.MatcherAssert.assertThat;
  import static org.hamcrest.Matchers.equalTo;
  
  import java.util.ArrayList;
  import java.util.Collections;
  import java.util.List;
  import java.util.concurrent.Callable;
  import java.util.concurrent.ExecutionException;
  import java.util.concurrent.ExecutorService;
  import java.util.concurrent.Executors;
  import java.util.concurrent.Future;
  import java.util.concurrent.TimeoutException;
  import java.util.concurrent.atomic.AtomicBoolean;
  import org.apache.beam.sdk.metrics.MetricName;
  import org.junit.Before;
  import org.junit.Test;
  import org.junit.runner.RunWith;
  import org.junit.runners.JUnit4;
  
  /** Tests for {@link DeltaCounterCell}. */
  @RunWith(JUnit4.class)
  public class DeltaCounterCellTest {
  
    private DeltaCounterCell cell;
  
    @Before
    public void setUp() {
      cell = new DeltaCounterCell(MetricName.named("hello", "world"));
    }
  
    @Test
    public void testDelta() {
      cell.inc(5);
      cell.inc(7);
      assertThat(cell.getSumAndReset(), equalTo(12L));
      assertThat(cell.getSumAndReset(), equalTo(0L));
  
      cell.inc(5);
      assertThat(cell.getSumAndReset(), equalTo(5L));
    }
  
    /**
     * Ensure that incrementing and getSumAndRest are correct under concurrent reader and writer
     * threads.
     */
    @Test(timeout = 30 * 1000)
    public void testAtomicSumAndReset()
        throws InterruptedException, ExecutionException, TimeoutException {
      long updatesPerWriter = 10_000;
      int numReaders = 3;
      int numWriters = 5;
      ExecutorService executor = Executors.newFixedThreadPool(numReaders + numWriters);
      AtomicBoolean doneWriting = new AtomicBoolean(false);
  
      Callable<Long> reader =
          () -> {
            long count = 0;
            boolean isLastRead;
            do {
              isLastRead = doneWriting.get();
              count += cell.getSumAndReset();
            } while (!isLastRead);
            return count;
          };
      Runnable writer =
          () -> {
            for (int i = 0; i < updatesPerWriter; i++) {
              cell.inc();
            }
          };
  
      // NB: Readers are invoked before writers to ensure they execute
      // concurrently.
      List<Future<Long>> results = new ArrayList<>(numReaders);
      for (int i = 0; i < numReaders; i++) {
        results.add(executor.submit(reader));
      }
  
      executor.invokeAll(Collections.nCopies(numWriters, Executors.callable(writer, 0L)));
      doneWriting.set(true);
  
      long count = 0;
      for (Future<Long> result : results) {
        count += result.get();
      }
      assertThat(count, equalTo(numWriters * updatesPerWriter));
    }
  }
  