runners/spark/src/main/java/org/apache/beam/runners/spark/util/SideInputStorage.java

/*
 * 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.spark.util;

import java.util.Objects;
import java.util.concurrent.TimeUnit;
import org.apache.beam.sdk.transforms.windowing.BoundedWindow;
import org.apache.beam.sdk.values.PCollectionView;
import org.apache.beam.vendor.guava.v26_0_jre.com.google.common.cache.Cache;
import org.apache.beam.vendor.guava.v26_0_jre.com.google.common.cache.CacheBuilder;

/**
 * Cache deserialized side inputs for executor so every task doesn't need to deserialize them again.
 * Side inputs are stored in {@link Cache} with 5 minutes expireAfterAccess.
 */
class SideInputStorage {

  /** JVM deserialized side input cache. */
  private static final Cache<Key<?>, Value<?>> materializedSideInputs =
      CacheBuilder.newBuilder().expireAfterAccess(5, TimeUnit.MINUTES).build();

  static Cache<Key<?>, Value<?>> getMaterializedSideInputs() {
    return materializedSideInputs;
  }

  /**
   * Composite key of {@link PCollectionView} and {@link BoundedWindow} used to identify
   * materialized results.
   *
   * @param <T> type of result
   */
  public static class Key<T> {

    private final PCollectionView<T> view;
    private final BoundedWindow window;

    Key(PCollectionView<T> view, BoundedWindow window) {
      this.view = view;
      this.window = window;
    }

    @Override
    public boolean equals(Object o) {
      if (this == o) {
        return true;
      }
      if (o == null || getClass() != o.getClass()) {
        return false;
      }
      Key<?> key = (Key<?>) o;
      return Objects.equals(view, key.view) && Objects.equals(window, key.window);
    }

    @Override
    public int hashCode() {
      return Objects.hash(view, window);
    }

    @Override
    public String toString() {
      String pName = view.getPCollection() != null ? view.getPCollection().getName() : "Unknown";
      return "Key{"
          + "view="
          + view.getTagInternal()
          + " of PCollection["
          + pName
          + "], window="
          + window
          + '}';
    }
  }

  /**
   * Null value is not allowed in guava's Cache and is valid in SideInput so we use wrapper for
   * cache value.
   */
  public static class Value<T> {
    final T value;

    Value(T value) {
      this.value = value;
    }

    public T getValue() {
      return value;
    }
  }
}