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From "Hiram Chirino" <>
Subject Re: Proposed refactoring to allow alternative persistence mechanisms
Date Fri, 11 Aug 2006 14:08:36 GMT
Please submit that patch!

On 8/10/06, Fateev, Maxim <> wrote:
>         Hi,
>         We were looking at alternate message persistence mechanisms that can co-exist
in current ActiveMQ code base and we are thinking of a mechanism that is somewhat incompatible
with the current MessageStore and PersistenceAdapter APIs. Unfortunately, the current ActiveMQ
broker doesn't allow for such a change as the PersistenceAdapter and MessageStore interfaces
are referenced directly by the RegionBroker and by both the Queue and Topic region implementations.
Therefore, we are proposing a relatively small backwards compatible refactoring of the broker
code that would eliminate all dependencies on the PersistenceAdapter and MessageStore interfaces
from those classes that do not use them directly. This refactoring would also allow creation
of a custom Destination implementation that may use an alternative persistence mechanism on
a destination by destination basis (which is exactly what we need to do).
>         The main idea behind the refactoring is to replace many references to PersistenceAdapter
with a new interface: DestinationFactory:
>         public abstract class DestinationFactory {
>         abstract public Destination createDestination(ConnectionContext context, ActiveMQDestination
destination, DestinationStatistics destinationStatistics) throws Exception;
>         abstract public Set getDestinations();
>         abstract public SubscriptionInfo[] getAllDurableSubscriptions(ActiveMQTopic topic)
throws IOException;
>         abstract public long getLastMessageBrokerSequenceId() throws IOException;
>         abstract public void setRegionBroker(RegionBroker regionBroker);
>         }
>         Note that DestinationFactory doesn't mandate any specific persistence mechanism.
The classes that would reference it instead of PersistenceAdapter are: RegionBroker, AbstractRegion,
QueueRegion, and TopicRegion. Also, the AbstractRegion.createDestination method would be changed
from abstract to an implementation that uses DestinationFactory to create a destination.
>         BrokerService could be changed to use DestinationFactory if one is provided.
If none is provided, it will create a DestinationFactory implementation that instantiates
Queue and Topic using PersistenceAdapter as it does currently. Hence, full backwards compatibility
will be maintained.
>         We have a preliminary implementation on local workspace. We can provide full
patch for review. Appreciate your thoughts.
>         Thanks
>         Maxim Fateev.



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