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From Rob Davies <rajdav...@gmail.com>
Subject Re: Advisory topic leakages (second theory)
Date Tue, 10 Jul 2007 05:36:05 GMT
hi Manuel,

on the face of it - this does look like an issue was introduced by  
the change in trunk  you mentioned. I think the code was changed to  
help some concurrency issues. However, the broker has changed  
considerably since then, so I'm not sure it still applies. The best  
thing to do would be to apply your patch + rollback the change in  
AbstractBroker you highlighted, and see if anything breaks ;)

cheers,

Rob

On Jul 9, 2007, at 1:57 PM, Manuel Teira wrote:

> And even worse, creating the destination in this way (inside the  
> TopicRegion) is not going to make the RegionBroker aware of it.  
> Since the AdvisoryBroker is relaying in the broker chain to try to  
> delete the consumer and producer advisory topics when a destination  
> is deleted, how and when are they supposed to be deleted in the  
> trunk code?
>
> Regards.
>
>
>
> Manuel Teira escribió:
>> Hi again.
>>
>> I'm afraid that the lookup code in AbstractRegion has being  
>> changed in the trunk (I was looking at 4.1 branch). Basically,  
>> instead of calling context.getBroker().addDestination 
>> (context,destination) to create the new destination, addDestination 
>> (context, destination) is used. This way, the advisory topic won't  
>> be created from top, but what happens with the advise in the code?
>>
>>                if(autoCreateDestinations){
>>                    // Try to auto create the destination... re- 
>> invoke broker from the
>>                    // top so that the proper security checks are  
>> performed.
>>                    try {
>>                        dest = addDestination(context, destination);
>>                        //context.getBroker().addDestination 
>> (context,destination);
>>                    }
>> I suppose that the assumption is no longer true.
>>
>> Also, the way to change this code (only commenting out the old  
>> one) makes me think about a not too mature change?
>>
>> If you can verify that this is the right way to proceed,I will  
>> like to prepare a patch against 4.1 branch.
>>
>>
>> Best regards.
>>
>>
>> Manuel Teira escribió:
>>> Hello again. Digging into the problem I've found another thing  
>>> related with an asymmetry in the way an advisory topic  is  
>>> created and destroyed.
>>>
>>> I'm analizying the way the Consumer and Producer advisory topics  
>>> for temporary queues are created and destroyed:
>>>
>>> An advisory topic is actually created when the AdvisoryBroker  
>>> fireAdvisory method is eventually sending the message. This is  
>>> happening in AbstractRegion lookup method, as the advisory topic  
>>> doesn't exist yet:
>>>
>>>    protected Destination lookup(ConnectionContext context,  
>>> ActiveMQDestination destination) throws Exception {
>>>        synchronized(destinationsMutex){
>>>            Destination dest=(Destination) destinations.get 
>>> (destination);
>>>            if(dest==null){
>>>                if(autoCreateDestinations){
>>>                    // Try to auto create the destination... re- 
>>> invoke broker from the
>>>                    // top so that the proper security checks are  
>>> performed.
>>>                    context.getBroker().addDestination 
>>> (context,destination);
>>>                    // We should now have the dest created.
>>>                    dest=(Destination) destinations.get(destination);
>>>                }
>>>                if(dest==null){
>>>                    throw new JMSException("The destination  
>>> "+destination+" does not exist.");
>>>                }
>>>            }
>>>            return dest;
>>>        }
>>>    }
>>>
>>> Hence, the whole Broker chain is called to create a destination  
>>> (context.getBroker().addDestination), this, in a common  
>>> environment, involves calling:
>>>
>>> MutableBrokerFilter.addDestination - Just pass the request to the  
>>> next chained BrokerFilter
>>> [
>>>   Here the configured plugins
>>> }
>>> CompositeDestinationBroker. No implementation, so it passes the  
>>> request to the next chained object.
>>> AdvisoryBroker. Fires an advisory to the destination advisory  
>>> topic, and adds the destination to its own destinations map.
>>> TransactionBroker.  No implementation, passes the request to the  
>>> next chained object.
>>> RegionBroker. Delegates in the TopicRegion.addDestination to  
>>> create the given advisory topic.
>>>
>>> On the other way, this advisory topic is destroyed when the  
>>> advised destination is removed, in AdvisoryTopic.  
>>> removeDestinationInfo. But here, the way to do it is:
>>>
>>>    public void removeDestinationInfo(ConnectionContext context,  
>>> DestinationInfo destInfo) throws Exception{
>>>        next.removeDestinationInfo(context, destInfo);
>>>        DestinationInfo info = (DestinationInfo)  
>>> destinations.remove(destInfo.getDestination());
>>>
>>>        if( info !=null ) {
>>>            info.setDestination(destInfo.getDestination());
>>>            info.setOperationType 
>>> (DestinationInfo.REMOVE_OPERATION_TYPE);
>>>            ActiveMQTopic topic =  
>>> AdvisorySupport.getDestinationAdvisoryTopic 
>>> (destInfo.getDestination());
>>>            fireAdvisory(context, topic, info);
>>>            try {
>>>                next.removeDestination(context,  
>>> AdvisorySupport.getConsumerAdvisoryTopic(info.getDestination()),  
>>> -1);
>>>            } catch (Exception expectedIfDestinationDidNotExistYet) {
>>>            }
>>>            try {
>>>                next.removeDestination(context,  
>>> AdvisorySupport.getProducerAdvisoryTopic(info.getDestination()),  
>>> -1);
>>>            } catch (Exception expectedIfDestinationDidNotExistYet) {
>>>            }
>>>        }
>>>
>>>    }
>>>
>>>
>>> So, only the next chained broker components to AdvisoryBroker are  
>>> called to remove the consumer and producer advisory topics. This  
>>> way to proceed suggests me two problems:
>>>
>>> 1.-The advisory broker itself is not aware of the deletion of  
>>> those topics (remember that it had registered them when the whole  
>>> broker chain was called to create the topic). I think that this  
>>> is the leakage I'm suffering.
>>> 2.-Any plugin (or component in the chain preceding the  
>>> AdvisoryBroker) that could be creating and retaining objects  
>>> related with these advisory topics won't never be able to release  
>>> them.
>>>
>>> Perhaps this way to proceed could be related with the fix of  
>>> AMQ-677.
>>>
>>> Did I miss anything?
>>>
>>> Regards.
>>>
>>>
>>>
>>
>>
>



Rob Davies
'Go further faster with Apache Camel!'
http://rajdavies.blogspot.com/




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