HowlMessageStore xref

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    1   /***
    2    *
    3    * Copyright 2004 Protique Ltd
    4    *
    5    * Licensed under the Apache License, Version 2.0 (the "License");
    6    * you may not use this file except in compliance with the License.
    7    * You may obtain a copy of the License at
    8    *
    9    * http://www.apache.org/licenses/LICENSE-2.0
    10   *
    11   * Unless required by applicable law or agreed to in writing, software
    12   * distributed under the License is distributed on an "AS IS" BASIS,
    13   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    14   * See the License for the specific language governing permissions and
    15   * limitations under the License.
    16   *
    17   **/
    18  package org.codehaus.activemq.store.howl;
    19
    20  import org.apache.commons.logging.Log;
    21  import org.apache.commons.logging.LogFactory;
    22  import org.codehaus.activemq.message.ActiveMQMessage;
    23  import org.codehaus.activemq.message.MessageAck;
    24  import org.codehaus.activemq.message.Packet;
    25  import org.codehaus.activemq.message.WireFormat;
    26  import org.codehaus.activemq.service.MessageIdentity;
    27  import org.codehaus.activemq.service.QueueMessageContainer;
    28  import org.codehaus.activemq.store.MessageStore;
    29  import org.codehaus.activemq.util.Callback;
    30  import org.codehaus.activemq.util.JMSExceptionHelper;
    31  import org.codehaus.activemq.util.TransactionTemplate;
    32  import org.objectweb.howl.log.LogConfigurationException;
    33  import org.objectweb.howl.log.LogException;
    34  import org.objectweb.howl.log.LogRecord;
    35  import org.objectweb.howl.log.Logger;
    36  import org.objectweb.howl.log.ReplayListener;
    37
    38  import javax.jms.JMSException;
    39  import java.io.IOException;
    40  import java.util.LinkedHashMap;
    41  import java.util.Map;
    42
    43  /***
    44   * An implementation of {@link MessageStore} designed for
    45   * optimal use with <a href="http://howl.objectweb.org/">Howl</a>
    46   * as the transaction log and then checkpointing asynchronously
    47   * on a timeout with some other persistent storage.
    48   *
    49   * @version $Revision: 1.3 $
    50   */
    51  public class HowlMessageStore implements MessageStore {
    52
    53      private static final int DEFAULT_RECORD_SIZE = 64 * 1024;
    54      private static final Log log = LogFactory.getLog(HowlMessageStore.class);
    55
    56      private HowlPersistenceAdapter longTermPersistence;
    57      private MessageStore longTermStore;
    58      private Logger transactionLog;
    59      private WireFormat wireFormat;
    60      private TransactionTemplate transactionTemplate;
    61      private int maximumCacheSize = 100;
    62      private Map map = new LinkedHashMap();
    63      private boolean sync = true;
    64      private long lastLogMark;
    65      private Exception firstException;
    66
    67      public HowlMessageStore(HowlPersistenceAdapter adapter, MessageStore checkpointStore, Logger transactionLog, WireFormat wireFormat) {
    68          this.longTermPersistence = adapter;
    69          this.longTermStore = checkpointStore;
    70          this.transactionLog = transactionLog;
    71          this.wireFormat = wireFormat;
    72          this.transactionTemplate = new TransactionTemplate(adapter);
    73      }
    74
    75
    76      /***
    77       * This method is synchronized to ensure that only 1 thread can write to the log and cache
    78       * and possibly checkpoint at once, to preserve order across the transaction log,
    79       * cache and checkpointStore.
    80       */
    81      public synchronized MessageIdentity addMessage(ActiveMQMessage message) throws JMSException {
    82          // write to howl
    83          writePacket(message);
    84
    85          // can we add it to the cache?
    86          if (!addMessageToCache(message)) {
    87              log.warn("Not enough RAM to store the active transaction log and so we're having to force" +
    88                      "a checkpoint so that we can ensure that reads are efficient and do not have to " +
    89                      "replay the transaction log");
    90              checkpoint(message);
    91
    92              // now lets add the current message to the checkpoint store
    93              longTermStore.addMessage(message);
    94          }
    95          return message.getJMSMessageIdentity();
    96      }
    97
    98      /***
    99       * Lets ensure that readers don't block writers so there only synchronization on
    100      * the cache and checkpointStore.
    101      */
    102     public ActiveMQMessage getMessage(MessageIdentity identity) throws JMSException {
    103         ActiveMQMessage answer = null;
    104         synchronized (map) {
    105             answer = (ActiveMQMessage) map.get(identity.getMessageID());
    106         }
    107         if (answer == null) {
    108             answer = longTermStore.getMessage(identity);
    109         }
    110         return answer;
    111     }
    112
    113     /***
    114      * Removes can be done in any order so we only synchronize on the cache and
    115      * checkpointStore
    116      */
    117     public void removeMessage(MessageIdentity identity, MessageAck ack) throws JMSException {
    118         // write to howl
    119         writePacket(ack);
    120
    121         synchronized (map) {
    122             map.remove(identity.getMessageID());
    123         }
    124         longTermPersistence.onMessageRemove(this);
    125     }
    126
    127     /***
    128      * Replays the checkpointStore first as those messages are the oldest ones,
    129      * then messages are replayed from the transaction log and then
    130      * the cache is updated.
    131      *
    132      * @param container
    133      * @throws JMSException
    134      */
    135     public synchronized void recover(final QueueMessageContainer container) throws JMSException {
    136         longTermStore.recover(container);
    137
    138         // replay the transaction log, updating the cache and adding any messages to be dispatched
    139         // to the container
    140         firstException = null;
    141         try {
    142             transactionLog.replay(new ReplayListener() {
    143                 LogRecord record = new LogRecord(DEFAULT_RECORD_SIZE);
    144
    145                 public void onRecord(LogRecord logRecord) {
    146                     readPacket(logRecord, container);
    147                 }
    148
    149                 public void onError(LogException e) {
    150                     log.error("Error while recovering Howl transaction log: " + e, e);
    151                 }
    152
    153                 public LogRecord getLogRecord() {
    154                     return record;
    155                 }
    156             });
    157         }
    158         catch (LogConfigurationException e) {
    159             throw createRecoveryFailedException(e);
    160         }
    161         if (firstException != null) {
    162             if (firstException instanceof JMSException) {
    163                 throw (JMSException) firstException;
    164             }
    165             else {
    166                 throw createRecoveryFailedException(firstException);
    167             }
    168         }
    169     }
    170
    171     public synchronized void start() throws JMSException {
    172         longTermStore.start();
    173     }
    174
    175     public synchronized void stop() throws JMSException {
    176         longTermStore.stop();
    177     }
    178
    179     /***
    180      * Writes the current RAM cache to the long term, checkpoint store so that the
    181      * transaction log can be truncated.
    182      */
    183     public synchronized void checkpoint() throws JMSException {
    184         checkpoint(null);
    185     }
    186
    187
    188     // Properties
    189     //-------------------------------------------------------------------------
    190     public int getMaximumCacheSize() {
    191         return maximumCacheSize;
    192     }
    193
    194     public void setMaximumCacheSize(int maximumCacheSize) {
    195         this.maximumCacheSize = maximumCacheSize;
    196     }
    197
    198     // Implementation methods
    199     //-------------------------------------------------------------------------
    200
    201     /***
    202      * Writes the current RAM image of the transaction log to stable, checkpoint store
    203      *
    204      * @param message is an optional message. This is null for timer based
    205      *                checkpoints or is the message which cannot fit into the cache if cache-exhaustion
    206      *                based checkpoints
    207      * @throws JMSException
    208      */
    209     protected void checkpoint(final ActiveMQMessage message) throws JMSException {
    210         // lets create a copy of the collection to avoid blocking readers
    211         ActiveMQMessage[] temp = null;
    212         synchronized (map) {
    213             temp = new ActiveMQMessage[map.size()];
    214             map.values().toArray(temp);
    215
    216             // lets clear the map so that its next contents represent
    217             // the stuff we need to checkpoint next time around
    218             map.clear();
    219         }
    220
    221         final ActiveMQMessage[] data = temp;
    222         transactionTemplate.run(new Callback() {
    223             public void execute() throws Throwable {
    224                 for (int i = 0, size = data.length; i < size; i++) {
    225                     longTermStore.addMessage(data[i]);
    226                 }
    227                 if (message != null) {
    228                     longTermStore.addMessage(message);
    229                 }
    230             }
    231         });
    232
    233         try {
    234             transactionLog.mark(lastLogMark);
    235         }
    236         catch (Exception e) {
    237             throw JMSExceptionHelper.newJMSException("Failed to checkpoint the Howl transaction log: " + e, e);
    238         }
    239     }
    240
    241     /***
    242      * Adds the given message to the cache if there is spare capacity
    243      *
    244      * @param message
    245      * @return true if the message was added to the cache or false
    246      */
    247     protected boolean addMessageToCache(ActiveMQMessage message) {
    248         synchronized (map) {
    249             if (map.size() < maximumCacheSize && longTermPersistence.hasCacheCapacity(this)) {
    250                 map.put(message.getJMSMessageID(), message);
    251                 return true;
    252             }
    253         }
    254         return false;
    255     }
    256
    257     protected void readPacket(LogRecord logRecord, QueueMessageContainer container) {
    258         if (!logRecord.isCTRL() && !logRecord.isEOB() && logRecord.length > 0) {
    259             try {
    260                 // TODO for some wierd reason we get an unnecessary long which I'm guessing is the size
    261                 Packet packet = wireFormat.fromBytes(logRecord.data, 2, logRecord.length - 2);
    262                 if (packet instanceof ActiveMQMessage) {
    263                     container.addMessage((ActiveMQMessage) packet);
    264                 }
    265                 else if (packet instanceof MessageAck) {
    266                     MessageAck ack = (MessageAck) packet;
    267                     container.delete(ack.getMessageIdentity(), ack);
    268                 }
    269                 else {
    270                     log.error("Unknown type of packet in transaction log which will be discarded: " + packet);
    271                 }
    272             }
    273             catch (Exception e) {
    274                 if (firstException == null) {
    275                     firstException = e;
    276                 }
    277             }
    278         }
    279     }
    280
    281     /***
    282      * Writes a message to the transaction log using the current sync mode
    283      */
    284     protected synchronized void writePacket(Packet packet) throws JMSException {
    285         try {
    286             byte[] data = wireFormat.toBytes(packet);
    287             lastLogMark = transactionLog.put(data, sync);
    288         }
    289         catch (IOException e) {
    290             throw createWriteException(packet, e);
    291         }
    292         catch (LogException e) {
    293             throw createWriteException(packet, e);
    294         }
    295         catch (InterruptedException e) {
    296             throw createWriteException(packet, e);
    297         }
    298     }
    299
    300
    301     protected JMSException createRecoveryFailedException(Exception e) {
    302         return JMSExceptionHelper.newJMSException("Failed to recover from Howl transaction log. Reason: " + e, e);
    303     }
    304
    305     protected JMSException createWriteException(Packet packet, Exception e) {
    306         return JMSExceptionHelper.newJMSException("Failed to write to Howl transaction log for: " + packet + ". Reason: " + e, e);
    307     }
    308 }