org.hornetq.core.server.impl.LastValueQueue Maven / Gradle / Ivy

/*
 * Copyright 2009 Red Hat, Inc.
 * Red Hat 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.hornetq.core.server.impl;

import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.Executor;
import java.util.concurrent.ScheduledExecutorService;

import org.hornetq.api.core.Message;
import org.hornetq.api.core.SimpleString;
import org.hornetq.core.filter.Filter;
import org.hornetq.core.logging.Logger;
import org.hornetq.core.persistence.StorageManager;
import org.hornetq.core.postoffice.PostOffice;
import org.hornetq.core.server.MessageReference;
import org.hornetq.core.server.Queue;
import org.hornetq.core.server.ServerMessage;
import org.hornetq.core.settings.HierarchicalRepository;
import org.hornetq.core.settings.impl.AddressSettings;

/**
 * A queue that will discard messages if a newer message with the same MessageImpl.HDR_LAST_VALUE_NAME property value.
 * In other words it only retains the last value
 * 
 * This is useful for example, for stock prices, where you're only interested in the latest value
 * for a particular stock
 * 
 * @author Andy Taylor
 * @author Tim Fox rewrite
 */
public class LastValueQueue extends QueueImpl
{
   private static final Logger log = Logger.getLogger(LastValueQueue.class);

   private final Map map = new ConcurrentHashMap();

   public LastValueQueue(final long persistenceID,
                         final SimpleString address,
                         final SimpleString name,
                         final Filter filter,
                         final boolean durable,
                         final boolean temporary,
                         final ScheduledExecutorService scheduledExecutor,
                         final PostOffice postOffice,
                         final StorageManager storageManager,
                         final HierarchicalRepository addressSettingsRepository,
                         final Executor executor)
   {
      super(persistenceID,
            address,
            name,
            filter,
            durable,
            temporary,
            scheduledExecutor,
            postOffice,
            storageManager,
            addressSettingsRepository,
            executor);
   }

   @Override
   public synchronized void add(final MessageReference ref, final boolean first, final boolean direct)
   {
      SimpleString prop = ref.getMessage().getSimpleStringProperty(Message.HDR_LAST_VALUE_NAME);

      if (prop != null)
      {
         HolderReference hr = map.get(prop);

         if (!first)
         {
            if (hr != null)
            {
               // We need to overwrite the old ref with the new one and ack the old one

               MessageReference oldRef = hr.getReference();

               super.referenceHandled();

               try
               {
                  super.acknowledge(oldRef);
               }
               catch (Exception e)
               {
                  LastValueQueue.log.error("Failed to ack old reference", e);
               }

               hr.setReference(ref);

            }
            else
            {
               hr = new HolderReference(prop, ref);

               map.put(prop, hr);

               super.add(hr, first, direct);
            }
         }
         else
         {
            // Add to front

            if (hr != null)
            {
               // We keep the current ref and ack the one we are returning

               super.referenceHandled();

               try
               {
                  super.acknowledge(ref);
               }
               catch (Exception e)
               {
                  LastValueQueue.log.error("Failed to ack old reference", e);
               }
            }
            else
            {
               map.put(prop, (HolderReference)ref);

               super.add(ref, first, direct);
            }
         }
      }
      else
      {
         super.add(ref, first, direct);
      }
   }

   private class HolderReference implements MessageReference
   {
      private final SimpleString prop;

      private volatile MessageReference ref;

      HolderReference(final SimpleString prop, final MessageReference ref)
      {
         this.prop = prop;

         this.ref = ref;
      }

      MessageReference getReference()
      {
         return ref;
      }

      public void handled()
      {
         // We need to remove the entry from the map just before it gets delivered

         map.remove(prop);
      }

      void setReference(final MessageReference ref)
      {
         this.ref = ref;
      }

      public MessageReference copy(final Queue queue)
      {
         return ref.copy(queue);
      }

      public void decrementDeliveryCount()
      {
         ref.decrementDeliveryCount();
      }

      public int getDeliveryCount()
      {
         return ref.getDeliveryCount();
      }

      public ServerMessage getMessage()
      {
         return ref.getMessage();
      }

      public Queue getQueue()
      {
         return ref.getQueue();
      }

      public long getScheduledDeliveryTime()
      {
         return ref.getScheduledDeliveryTime();
      }

      public void incrementDeliveryCount()
      {
         ref.incrementDeliveryCount();
      }

      public void setDeliveryCount(final int deliveryCount)
      {
         ref.setDeliveryCount(deliveryCount);
      }

      public void setScheduledDeliveryTime(final long scheduledDeliveryTime)
      {
         ref.setScheduledDeliveryTime(scheduledDeliveryTime);
      }
   }
}