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.core;
  
  import org.apache.beam.runners.core.metrics.CounterCell;
  import org.apache.beam.sdk.transforms.windowing.BoundedWindow;
  import org.apache.beam.sdk.transforms.windowing.GlobalWindow;
  import org.apache.beam.sdk.util.WindowTracing;
  import org.apache.beam.sdk.values.WindowedValue;
  import org.apache.beam.sdk.values.WindowingStrategy;
  import org.apache.beam.vendor.guava.v32_1_2_jre.com.google.common.collect.FluentIterable;
  import org.apache.beam.vendor.guava.v32_1_2_jre.com.google.common.collect.Iterables;
  import org.joda.time.Duration;
  import org.joda.time.Instant;
  
  /** Utils to handle late data. */
  @SuppressWarnings({
    "rawtypes", // TODO(https://github.com/apache/beam/issues/20447)
    "nullness",
    "keyfor"
  }) // TODO(https://github.com/apache/beam/issues/20497)
  public class LateDataUtils {
    private LateDataUtils() {}
  
    /**
     * Return when {@code window} should be garbage collected. If the window's expiration time is on
     * or after the end of the global window, it will be truncated to the end of the global window.
     */
    public static Instant garbageCollectionTime(
        BoundedWindow window, WindowingStrategy windowingStrategy) {
      return garbageCollectionTime(window, windowingStrategy.getAllowedLateness());
    }
  
    /**
     * Return when {@code window} should be garbage collected. If the window's expiration time is on
     * or after the end of the global window, it will be truncated to the end of the global window.
     */
    public static Instant garbageCollectionTime(BoundedWindow window, Duration allowedLateness) {
  
      // If the end of the window + allowed lateness is beyond the "end of time" aka the end of the
      // global window, then we truncate it. The conditional is phrased like it is because the
      // addition of EOW + allowed lateness might even overflow the maximum allowed Instant
      if (GlobalWindow.INSTANCE
          .maxTimestamp()
          .minus(allowedLateness)
          .isBefore(window.maxTimestamp())) {
        return GlobalWindow.INSTANCE.maxTimestamp();
      } else {
        return window.maxTimestamp().plus(allowedLateness);
      }
    }
  
    /**
     * Returns an {@code Iterable<WindowedValue<InputT>>} that only contains non-late input elements.
     */
    public static <K, V> Iterable<WindowedValue<V>> dropExpiredWindows(
        final K key,
        Iterable<WindowedValue<V>> elements,
        final TimerInternals timerInternals,
        final WindowingStrategy<?, ?> windowingStrategy,
        final CounterCell droppedDueToLateness) {
      return FluentIterable.from(elements)
          .transformAndConcat(
              // Explode windows to filter out expired ones
              input -> {
                if (input == null) {
                  return null;
                }
                // The generics in this chain of calls line up best if we drop the covariance
                // in the return value of explodeWindows()
                return (Iterable<WindowedValue<V>>) input.explodeWindows();
              })
          .filter(
              input -> {
                if (input == null) {
                  // drop null elements.
                  return false;
                }
                BoundedWindow window = Iterables.getOnlyElement(input.getWindows());
                boolean expired =
                    window
                        .maxTimestamp()
                        .plus(windowingStrategy.getAllowedLateness())
                        .isBefore(timerInternals.currentInputWatermarkTime());
                if (expired) {
                  // The element is too late for this window.
                  droppedDueToLateness.inc();
                  WindowTracing.debug(
                      "GroupAlsoByWindow: Dropping element at {} for key: {}; "
                          + "window: {} since it is too far behind inputWatermark: {}",
                      input.getTimestamp(),
                      key,
                      window,
                      timerInternals.currentInputWatermarkTime());
                }
                // Keep the element if the window is not expired.
                return !expired;
              });
    }
  }
  