001/**
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements.  See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache License, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License.  You may obtain a copy of the License at
008 *
009 *      http://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 */
017package org.apache.activemq.broker.region.cursors;
018
019import java.util.Iterator;
020import org.apache.activemq.broker.region.Destination;
021import org.apache.activemq.broker.region.MessageReference;
022import org.apache.activemq.command.Message;
023import org.apache.activemq.command.MessageId;
024import org.apache.activemq.store.MessageRecoveryListener;
025import org.slf4j.Logger;
026import org.slf4j.LoggerFactory;
027
028/**
029 *  Store based cursor
030 *
031 */
032public abstract class AbstractStoreCursor extends AbstractPendingMessageCursor implements MessageRecoveryListener {
033    private static final Logger LOG = LoggerFactory.getLogger(AbstractStoreCursor.class);
034    protected final Destination regionDestination;
035    private final PendingList batchList;
036    private Iterator<MessageReference> iterator = null;
037    protected boolean batchResetNeeded = true;
038    private boolean storeHasMessages = false;
039    protected int size;
040    private MessageId lastCachedId;
041    private boolean hadSpace = false;
042
043    protected AbstractStoreCursor(Destination destination) {
044        super((destination != null ? destination.isPrioritizedMessages():false));
045        this.regionDestination=destination;
046        if (this.prioritizedMessages) {
047            this.batchList= new PrioritizedPendingList();
048        } else {
049            this.batchList = new OrderedPendingList();
050        }
051    }
052    
053    
054    public final synchronized void start() throws Exception{
055        if (!isStarted()) {
056            clear();
057            super.start();      
058            resetBatch();
059            this.size = getStoreSize();
060            this.storeHasMessages=this.size > 0;
061            setCacheEnabled(!this.storeHasMessages&&useCache);
062        } 
063    }
064    
065    
066    public final synchronized void stop() throws Exception {
067        resetBatch();
068        super.stop();
069        gc();
070    }
071
072    
073    public final boolean recoverMessage(Message message) throws Exception {
074        return recoverMessage(message,false);
075    }
076    
077    public synchronized boolean recoverMessage(Message message, boolean cached) throws Exception {
078        boolean recovered = false;
079        if (recordUniqueId(message.getMessageId())) {
080            if (!cached) {
081                message.setRegionDestination(regionDestination);
082                if( message.getMemoryUsage()==null ) {
083                    message.setMemoryUsage(this.getSystemUsage().getMemoryUsage());
084                }
085            }
086            message.incrementReferenceCount();
087            batchList.addMessageLast(message);
088            clearIterator(true);
089            recovered = true;
090            storeHasMessages = true;
091        } else {
092            /*
093             * we should expect to get these - as the message is recorded as it before it goes into
094             * the cache. If subsequently, we pull out that message from the store (before its deleted)
095             * it will be a duplicate - but should be ignored
096             */
097            if (LOG.isTraceEnabled()) {
098                LOG.trace(this + " - cursor got duplicate: " + message.getMessageId() + ", " + message.getPriority());
099            }
100        }
101        return recovered;
102    }
103    
104    
105    public final void reset() {
106        if (batchList.isEmpty()) {
107            try {
108                fillBatch();
109            } catch (Exception e) {
110                LOG.error(this + " - Failed to fill batch", e);
111                throw new RuntimeException(e);
112            }
113        }
114        clearIterator(true);
115        size();
116    }
117    
118    
119    public synchronized void release() {
120        clearIterator(false);
121    }
122    
123    private synchronized void clearIterator(boolean ensureIterator) {
124        boolean haveIterator = this.iterator != null;
125        this.iterator=null;
126        if(haveIterator&&ensureIterator) {
127            ensureIterator();
128        }
129    }
130    
131    private synchronized void ensureIterator() {
132        if(this.iterator==null) {
133            this.iterator=this.batchList.iterator();
134        }
135    }
136
137
138    public final void finished() {
139    }
140        
141    
142    public final synchronized boolean hasNext() {
143        if (batchList.isEmpty()) {
144            try {
145                fillBatch();
146            } catch (Exception e) {
147                LOG.error(this + " - Failed to fill batch", e);
148                throw new RuntimeException(e);
149            }
150        }
151        ensureIterator();
152        return this.iterator.hasNext();
153    }
154    
155    
156    public final synchronized MessageReference next() {
157        MessageReference result = null;
158        if (!this.batchList.isEmpty()&&this.iterator.hasNext()) {
159            result = this.iterator.next();
160        }
161        last = result;
162        if (result != null) {
163            result.incrementReferenceCount();
164        }
165        return result;
166    }
167    
168    
169    public final synchronized void addMessageLast(MessageReference node) throws Exception {
170        if (hasSpace()) {
171            if (!isCacheEnabled() && size==0 && isStarted() && useCache) {
172                if (LOG.isTraceEnabled()) {
173                    LOG.trace(this + " - enabling cache for empty store " + node.getMessageId());
174                }
175                setCacheEnabled(true);
176            }
177            if (isCacheEnabled()) {
178                recoverMessage(node.getMessage(),true);
179                lastCachedId = node.getMessageId();
180            }
181        } else if (isCacheEnabled()) {
182            setCacheEnabled(false);
183            // sync with store on disabling the cache
184            if (lastCachedId != null) {
185                if (LOG.isTraceEnabled()) {
186                    LOG.trace(this + " - disabling cache"
187                            + ", lastCachedId: " + lastCachedId
188                            + " current node Id: " + node.getMessageId());
189                }
190                setBatch(lastCachedId);
191                lastCachedId = null;
192            }
193        }
194        this.storeHasMessages = true;
195        size++;
196    }
197
198    protected void setBatch(MessageId messageId) throws Exception {
199    }
200
201    
202    public final synchronized void addMessageFirst(MessageReference node) throws Exception {
203        setCacheEnabled(false);
204        size++;
205    }
206
207    
208    public final synchronized void remove() {
209        size--;
210        if (iterator!=null) {
211            iterator.remove();
212        }
213        if (last != null) {
214            last.decrementReferenceCount();
215        }
216    }
217
218    
219    public final synchronized void remove(MessageReference node) {
220        size--;
221        setCacheEnabled(false);
222        batchList.remove(node);
223    }
224    
225    
226    public final synchronized void clear() {
227        gc();
228    }
229    
230    
231    public synchronized void gc() {
232        for (Iterator<MessageReference>i = batchList.iterator();i.hasNext();) {
233            MessageReference msg = i.next();
234            rollback(msg.getMessageId());
235            msg.decrementReferenceCount();
236        }
237        batchList.clear();
238        clearIterator(false);
239        batchResetNeeded = true;
240        setCacheEnabled(false);
241    }
242
243    @Override
244    public boolean hasSpace() {
245        hadSpace = super.hasSpace();
246        return hadSpace;
247    }
248
249    protected final synchronized void fillBatch() {
250        if (LOG.isTraceEnabled()) {
251            LOG.trace(this + " - fillBatch");
252        }
253        if (batchResetNeeded) {
254            resetBatch();
255            this.batchResetNeeded = false;
256        }
257        if (this.batchList.isEmpty() && this.storeHasMessages && this.size >0) {
258            this.storeHasMessages = false;
259            try {
260                doFillBatch();
261            } catch (Exception e) {
262                LOG.error(this + " - Failed to fill batch", e);
263                throw new RuntimeException(e);
264            }
265            if (!this.batchList.isEmpty() || !hadSpace) {
266                this.storeHasMessages=true;
267            }
268        }
269    }
270    
271    
272    public final synchronized boolean isEmpty() {
273        // negative means more messages added to store through queue.send since last reset
274        return size == 0;
275    }
276
277    
278    public final synchronized boolean hasMessagesBufferedToDeliver() {
279        return !batchList.isEmpty();
280    }
281
282    
283    public final synchronized int size() {
284        if (size < 0) {
285            this.size = getStoreSize();
286        }
287        return size;
288    }
289
290    public String toString() {
291        return regionDestination.getActiveMQDestination().getPhysicalName() + ",batchResetNeeded=" + batchResetNeeded
292                    + ",storeHasMessages=" + this.storeHasMessages + ",size=" + this.size + ",cacheEnabled=" + isCacheEnabled();
293    }
294    
295    protected abstract void doFillBatch() throws Exception;
296    
297    protected abstract void resetBatch();
298    
299    protected abstract int getStoreSize();
300    
301    protected abstract boolean isStoreEmpty();
302}