library/src/main/java/org/apache/apex/malhar/lib/state/spillable/Spillable.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.apex.malhar.lib.state.spillable;

import java.util.List;
import java.util.Map;
import java.util.Queue;

import com.google.common.collect.ListMultimap;

import com.datatorrent.api.Component;
import com.datatorrent.api.Context.OperatorContext;

/**
 * This is a marker interface for a spillable data structure.
 *
 * @since 3.4.0
 */
public interface Spillable
{
  /**
   * This represents a spillable {@link java.util.List}. The underlying implementation
   * of this list is similar to that of an {@link java.util.ArrayList}. User's that receive an
   * implementation of this interface don't need to worry about propagating operator call-backs
   * to the data structure.
   * @param <T> The type of the data stored in the {@link SpillableArrayList}.
   */
  interface SpillableArrayList<T> extends List<T>
  {
  }

  /**
   * This represents a spillable {@link java.util.Map}. The underlying implementation
   * of this map uses the serialized representation of the key object as a key. User's that receive an
   * implementation of this interface don't need to worry about propagating operator call-backs
   * to the data structure.
   * @param <K> The type of the keys.
   * @param <V> The type of the values.
   */
  interface SpillableByteMap<K, V> extends Map<K, V>
  {
  }

  /**
   * This represents a spillable {@link com.google.common.collect.ListMultimap} implementation. User's that receive an
   * implementation of this interface don't need to worry about propagating operator call-backs
   * to the data structure.
   * @param <K> The type of the keys.
   * @param <V> The type of the values.
   */
  interface SpillableByteArrayListMultimap<K, V> extends ListMultimap<K, V>
  {
  }

  /**
   * This represents a spillable {@link java.util.Queue} implementation. User's that receive an
   * implementation of this interface don't need to worry about propagating operator call-backs
   * to the data structure.
   * @param <T> The type of the data stored in the queue.
   */
  interface SpillableQueue<T> extends Queue<T>
  {
  }

  /**
   * This represents a spillable data structure that needs to be aware of the operator
   * callbacks. All concrete or abstract implementations of spillable data structures
   * should implement this interface. A user working with an implementation of this interface needs
   * to make sure that the {@link com.datatorrent.api.Operator} call-backs are propagated to it.
   */
  interface SpillableComponent extends Component<OperatorContext>, Spillable
  {
    /**
     * This signals that the parent {@link com.datatorrent.api.Operator}'s
     * {@link com.datatorrent.api.Operator#beginWindow(long)} method has been called.
     * @param windowId The next windowId of the parent operator.
     */
    void beginWindow(long windowId);

    /**
     * This signals that the parent {@link com.datatorrent.api.Operator}'s
     * {@link com.datatorrent.api.Operator#endWindow()} method has been called.
     */
    void endWindow();
  }
}