/*
 * 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 org.apache.geode.distributed.Role;

import java.util.Set;

/**
 * A reliable message queue is used by a DistributedRegion to queue up distributed operations for
 * required roles that are not present at the time the operation is done. Instances of this
 * interface can be obtained from {@link ReliableMessageQueueFactory} which can be obtained from
 * {@link GemFireCacheImpl#getReliableMessageQueueFactory}.
 * 
 * @since GemFire 5.0
 */
public interface ReliableMessageQueue {
  /**
   * Returns the region this queue belongs to.
   */
  public DistributedRegion getRegion();

  /**
   * Adds a message to the queue to be sent to the list of roles.
   * 
   * @param data the actual data that describes the operation to enqueue
   * @param roles the roles that need to receive this message.
   */
  public void add(ReliableDistributionData data, Set roles);

  /**
   * Gets the roles that this queue currently has messages for.
   * 
   * @return a set of {link Role}s that currently have queued messages. <code>null</code> is
   *         returned if no messages are queued.
   */
  public Set getQueuingRoles();

  /**
   * Attempts to send any messages that have been added for the given role to all members that are
   * currently playing that role.
   * 
   * @param role the role whose queued messages should be sent
   * @return true if send was successful; false if it was not and the messages are still queued.
   */
  public boolean roleReady(Role role);

  /**
   * Removes all the data in this queue causing it to never be sent.
   */
  public void destroy();

  /**
   * Closes this queue. This frees up any memory used by the queue but its persistent data remains.
   */
  public void close();
}