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.
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  package org.apache.beam.sdk.fn.splittabledofn;
  
  import static org.junit.Assert.assertEquals;
  import static org.junit.Assert.assertFalse;
  
  import java.util.concurrent.CountDownLatch;
  import java.util.function.Consumer;
  import org.apache.beam.sdk.transforms.splittabledofn.TimestampObservingWatermarkEstimator;
  import org.apache.beam.sdk.transforms.splittabledofn.WatermarkEstimator;
  import org.apache.beam.sdk.transforms.windowing.GlobalWindow;
  import org.apache.beam.sdk.values.KV;
  import org.joda.time.Duration;
  import org.joda.time.Instant;
  import org.junit.Test;
  import org.junit.runner.RunWith;
  import org.junit.runners.JUnit4;
  
  /** Tests for {@link WatermarkEstimators}. */
  @RunWith(JUnit4.class)
  public class WatermarkEstimatorsTest {
    @Test
    public void testThreadSafeWatermarkEstimator() throws Exception {
      Instant[] reference = new Instant[] {GlobalWindow.TIMESTAMP_MIN_VALUE};
      WatermarkEstimator<Instant> watermarkEstimator =
          new WatermarkEstimator<Instant>() {
            private Instant currentWatermark = GlobalWindow.TIMESTAMP_MIN_VALUE;
  
            @Override
            public Instant currentWatermark() {
              currentWatermark = reference[0];
              return currentWatermark;
            }
  
            @Override
            public Instant getState() {
              return currentWatermark;
            }
          };
      testWatermarkEstimatorSnapshotsStateWithCompetingThread(
          WatermarkEstimators.threadSafe(watermarkEstimator), (instant) -> reference[0] = instant);
    }
  
    @Test
    public void testThreadSafeTimestampObservingWatermarkEstimator() throws Exception {
      WatermarkEstimators.WatermarkAndStateObserver<Instant> threadsafeWatermarkEstimator =
          WatermarkEstimators.threadSafe(
              new org.apache.beam.sdk.transforms.splittabledofn.WatermarkEstimators
                  .MonotonicallyIncreasing(GlobalWindow.TIMESTAMP_MIN_VALUE));
      testWatermarkEstimatorSnapshotsStateWithCompetingThread(
          threadsafeWatermarkEstimator,
          ((TimestampObservingWatermarkEstimator) threadsafeWatermarkEstimator)::observeTimestamp);
    }
  
    public <WatermarkEstimatorT extends WatermarkEstimators.WatermarkAndStateObserver<Instant>>
        void testWatermarkEstimatorSnapshotsStateWithCompetingThread(
            WatermarkEstimatorT watermarkEstimator, Consumer<Instant> watermarkUpdater)
            throws Exception {
      CountDownLatch countDownLatch = new CountDownLatch(1);
      Thread t =
          new Thread(
              () -> {
                countDownLatch.countDown();
                for (int i = 0; i < 1000; ++i) {
                  watermarkUpdater.accept(GlobalWindow.TIMESTAMP_MIN_VALUE.plus(Duration.millis(i)));
                }
              });
      t.start();
  
      // Ensure the thread has started before we start fetching values.
      countDownLatch.await();
      Instant currentMinimum = GlobalWindow.TIMESTAMP_MIN_VALUE;
      for (int i = 0; i < 100; ++i) {
        KV<Instant, Instant> value = watermarkEstimator.getWatermarkAndState();
        // The watermark estimators that we use ensure that state == current watermark so test that
        // they are equal here
        assertEquals(value.getKey(), value.getValue());
        // Also ensure that the watermark is not declining and somehow we are getting an "old" read
        assertFalse(currentMinimum.isAfter(value.getKey()));
      }
  
      t.join(10000);
    }
  }
  