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.
