geode-core/src/main/java/org/apache/geode/internal/cache/RegionQueue.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.geode.internal.cache;

import java.util.List;

import org.apache.geode.cache.CacheException;
import org.apache.geode.cache.CacheListener;
import org.apache.geode.cache.Region;

/**
 * Interface <code>RegionQueue</code> is an interface for queue implementations backed by regions.
 *
 *
 * @since GemFire 4.2
 */
public interface RegionQueue {

  /**
   * A token used to signify this is a WAN queue. It is set in the callback argument.
   */
  String WAN_QUEUE_TOKEN = "WAN_QUEUE_TOKEN";

  /**
   * Puts an object onto the tail of the queue
   *
   * @param object The object to put onto the queue
   *
   * @return boolean whether object was successfully put onto the queue
   */
  boolean put(Object object) throws InterruptedException, CacheException;

  /**
   * Returns the underlying region that backs this queue.
   */
  Region getRegion();

  /**
   * Takes the first object from the head of the queue. This method returns null if there are no
   * objects on the queue.
   *
   * @return The object taken
   *
   */
  Object take() throws CacheException, InterruptedException;

  /**
   * Takes up to batchSize number of objects from the head of the queue. As soon as it gets a null
   * response from a take, it stops taking.
   *
   * @param batchSize The number of objects to take from the queue
   *
   * @return the <code>List</code> of objects taken from the queue
   *
   */
  List take(int batchSize) throws CacheException, InterruptedException;

  /**
   * Removes a single object from the head of the queue without returning it. This method assumes
   * that the queue contains at least one object.
   *
   */
  void remove() throws InterruptedException, CacheException;

  /**
   * Peeks the first object from the head of the queue without removing it. This method returns null
   * if there are no objects on the queue.
   *
   * @return The object peeked
   */
  Object peek() throws InterruptedException, CacheException;

  /**
   * Peeks up to batchSize number of objects from the head of the queue without removing them. As
   * soon as it gets a null response from a peek, it stops peeking.
   *
   * @param batchSize The number of objects to peek from the queue
   *
   * @return The list of objects peeked
   */
  List peek(int batchSize) throws InterruptedException, CacheException;

  /**
   * Peeks either a batchSize number of elements from the queue or until timeToWait milliseconds
   * have elapsed (whichever comes first). If it has peeked batchSize number of elements from the
   * queue before timeToWait milliseconds have elapsed, it stops peeking. If timeToWait milliseconds
   * elapse before batchSize number of elements has been peeked, it stops.
   *
   * @param batchSize The number of objects to peek from the queue
   * @param timeToWait The number of milliseconds to attempt to peek
   *
   * @return The list of objects peeked
   *
   */
  List peek(int batchSize, int timeToWait) throws InterruptedException, CacheException;

  /**
   * Returns the size of the queue
   *
   * @return the size of the queue
   */
  int size();

  /**
   * Add a <code>CacheListener</code> to the queue
   *
   * @param listener The <code>CacheListener</code> to add
   */
  void addCacheListener(CacheListener listener);

  /**
   * Remove the <code>CacheListener</code> from the queue
   */
  void removeCacheListener();

  // TODO:Asif: Remove this method. Added this justto make it compilable
  void remove(int top) throws CacheException;

  void close();
}