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001 /**
002 * Licensed to the Apache Software Foundation (ASF) under one
003 * or more contributor license agreements. See the NOTICE file
004 * distributed with this work for additional information
005 * regarding copyright ownership. The ASF licenses this file
006 * to you under the Apache License, Version 2.0 (the
007 * "License"); you may not use this file except in compliance
008 * with the License. You may obtain a copy of the License at
009 *
010 * http://www.apache.org/licenses/LICENSE-2.0
011 *
012 * Unless required by applicable law or agreed to in writing, software
013 * distributed under the License is distributed on an "AS IS" BASIS,
014 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
015 * See the License for the specific language governing permissions and
016 * limitations under the License.
017 */
018 package org.apache.oozie.event;
019
020 import java.io.Serializable;
021 import java.util.List;
022
023 import org.apache.hadoop.conf.Configuration;
024 import org.apache.oozie.client.event.Event;
025
026 /**
027 * Interface to define the queue operations for the events system
028 */
029 public interface EventQueue {
030
031 public class EventQueueElement implements Serializable {
032
033 private static final long serialVersionUID = 1L;
034 Event event;
035
036 public EventQueueElement(Event e) {
037 event = e;
038 }
039 }
040
041 /**
042 * Initialize the event queue
043 * @param conf
044 */
045 public void init(Configuration conf);
046
047 /**
048 * Add event to queue
049 * @param event
050 */
051 public void add(Event e);
052
053 /**
054 * Fetch events from queue in batch
055 * @return events set
056 */
057 public List<Event> pollBatch();
058
059 /**
060 * Fetch single event from queue
061 * @return event
062 */
063 public Event poll();
064
065 /**
066 * Find out if queue is empty
067 * @return boolean
068 */
069 public boolean isEmpty();
070
071 /**
072 * Get current queue size
073 * @return size
074 */
075 public int size();
076
077 /**
078 * Read topmost event from queue but do not pop from it
079 * @return event
080 */
081 public Event peek();
082
083 /**
084 * Get the batch size used during polling events
085 * @return batchSize
086 */
087 public int getBatchSize();
088
089 /**
090 * Clear the events queue
091 */
092 public void clear();
093
094 }