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
019
020package org.apache.oozie.event;
021
022import java.util.ArrayList;
023import java.util.List;
024import java.util.concurrent.ConcurrentLinkedQueue;
025import java.util.concurrent.atomic.AtomicInteger;
026
027import org.apache.hadoop.conf.Configuration;
028import org.apache.oozie.client.event.Event;
029import org.apache.oozie.service.ConfigurationService;
030import org.apache.oozie.service.EventHandlerService;
031import org.apache.oozie.util.XLog;
032
033/**
034 * An implementation of the EventQueue, defining a memory-based data structure
035 * holding the events
036 */
037public class MemoryEventQueue implements EventQueue {
038
039    private static ConcurrentLinkedQueue<EventQueueElement> eventQueue;
040    private static AtomicInteger currentSize;
041    private static int maxSize;
042    private static XLog LOG;
043    private static int batchSize;
044
045    @Override
046    public void init(Configuration conf) {
047        eventQueue = new ConcurrentLinkedQueue<EventQueueElement>();
048        maxSize = ConfigurationService.getInt(conf, EventHandlerService.CONF_QUEUE_SIZE);
049        currentSize = new AtomicInteger();
050        batchSize = ConfigurationService.getInt(conf, EventHandlerService.CONF_BATCH_SIZE);
051        LOG = XLog.getLog(getClass());
052        LOG.info("Memory Event Queue initialized with Max size = [{0}], Batch drain size = [{1}]", maxSize, batchSize);
053    }
054
055    @Override
056    public int getBatchSize() {
057        return batchSize;
058    }
059
060    @Override
061    public void add(Event e) {
062        EventQueueElement eqe = new EventQueueElement(e);
063        try {
064            if (size() <= maxSize) {
065                if (eventQueue.add(eqe)) {
066                    currentSize.incrementAndGet();
067                }
068            }
069            else {
070                LOG.warn("Queue size [{0}] reached max limit. Element [{1}] not added", size(), e);
071            }
072        }
073        catch (IllegalStateException ise) {
074            LOG.warn("Unable to add event due to " + ise);
075        }
076    }
077
078    @Override
079    public List<Event> pollBatch() {
080        // batch drain
081        List<Event> eventBatch = new ArrayList<Event>();
082        for (int i = 0; i < batchSize; i++) {
083            EventQueueElement polled = eventQueue.poll();
084            if (polled != null) {
085                currentSize.decrementAndGet();
086                eventBatch.add(polled.event);
087            }
088            else {
089                LOG.trace("Current queue size [{0}] less than polling batch size [{1}]", currentSize.get(), batchSize);
090                break;
091            }
092        }
093        return eventBatch;
094    }
095
096    @Override
097    public Event poll() {
098        EventQueueElement polled = eventQueue.poll();
099        if (polled != null) {
100            currentSize.decrementAndGet();
101            return polled.event;
102        }
103        return null;
104    }
105
106    @Override
107    public boolean isEmpty() {
108        return size() == 0;
109    }
110
111    @Override
112    public int size() {
113        return currentSize.intValue();
114    }
115
116    @Override
117    public Event peek() {
118        EventQueueElement peeked = eventQueue.peek();
119        if (peeked != null) {
120            return peeked.event;
121        }
122        return null;
123    }
124
125    @Override
126    public void clear() {
127        eventQueue.clear();
128        currentSize.set(0);
129    }
130
131}