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From David Sitsky <s...@nuix.com>
Subject Re: Queue performance from recent changes
Date Mon, 17 Mar 2008 06:10:22 GMT
Hi Rob,

I've finally had some time to run some benchmarks with the trunk checked 
out today (637703) and the numbers look great!  Many thanks for checking 
in this code - I'm happy now that I don't have to maintain any of my own 
private modifications to activemq.

Thanks again.

Cheers,
David

David Sitsky wrote:
> Many thanks Rob - I'll try and do a fresh checkout today and let you 
> know how the performance looks using my standard benchmarks.
> 
> Cheers,
> David
> 
> Rob Davies wrote:
>> Hi David,
>>
>> the changes you suggested are now in and lazyDispatch can be set by a 
>> destination policy - its currently on by default
>>
>> cheers,
>>
>> Rob
>> On 6 Mar 2008, at 05:54, David Sitsky wrote:
>>
>>> Hi Rob,
>>>
>>> I know its been a couple of weeks.  I've been using my changes for a 
>>> while and I see nice CPU and memory usage on the broker, and good 
>>> messaging performance for my application.  Have you had a chance to 
>>> try it out?
>>>
>>> Cheers,
>>> David
>>>
>>> Rob Davies wrote:
>>>> Hi David,
>>>> thanks for the great feedback - will try your patch and see how it 
>>>> works!
>>>> cheers,
>>>> Rob
>>>> On 20 Feb 2008, at 06:31, David Sitsky wrote:
>>>>> Hi Rob,
>>>>>
>>>>> I like the new changes, but with the changes as they are, for my 
>>>>> application for one of my benchmarks, it takes twice as long to 
>>>>> complete.
>>>>>
>>>>> I believe the culprit for this is that when the new code can't find 
>>>>> a consumer which is not full, the broker chooses the consumer with 
>>>>> the lowest dispatch queue size.
>>>>>
>>>>> In my application, since I have a prefetch size of 1, and have 
>>>>> longish-running transactions, the dispatch queue size is not 
>>>>> indicative of the current load for that consumer.  As a result, I 
>>>>> think this is what is responsible for poor load-balancing in my case.
>>>>>
>>>>> For applications which commit() after each processed message, I am 
>>>>> sure this wouldn't be the case.  In some ways, reverting to the old 
>>>>> behaviour of adding the pending message to all consumers might lead 
>>>>> to better load balancing with this code.
>>>>>
>>>>> However - I think it is better if the consumers can decide when 
>>>>> they want more messages rather than the broker pushing messages at 
>>>>> them? I've attached a patch which demonstrates this.  When 
>>>>> LAZY_DISPATCH is set to true (set via a system property for now for 
>>>>> testing purposes) this changes the behaviour slightly.
>>>>>
>>>>> The basic idea is pageInMessages() only pages in the minimum number 
>>>>> of messages that can be dispatched immediately to non-full 
>>>>> consumers. Whenever a consumer acks a message, which updates its 
>>>>> prefetch size, we make sure Queue.wakeup() is called so that the 
>>>>> consumer will receive new messages.
>>>>>
>>>>> With this change in effect - I see slightly faster or almost the 
>>>>> same times with the previous benchmark.  However memory usage on 
>>>>> the broker is far better, as the pending queues for each consumer 
>>>>> is either 0 or very small.
>>>>>
>>>>> What do you think?  I guess there are better ways of doing this.
>>>>>
>>>>> I am doing a large overnight run with 16 consumers, so we'll see 
>>>>> how the  performance goes.
>>>>>
>>>>> You'll also notice in the patch, that in Queue.addSubscriber(), I 
>>>>> thought there didn't seem to be any need for adding a message to a 
>>>>> new consumer if the message has already been locked by another 
>>>>> consumer?
>>>>>
>>>>> Cheers,
>>>>> David
>>>>>
>>>>> Rob Davies wrote:
>>>>>> Hi David,
>>>>>> please let us know if these changes helps/hinders your app!
>>>>>> cheers,
>>>>>> Rob
>>>>>> On 19 Feb 2008, at 08:32, David Sitsky wrote:
>>>>>>>>> If what I said above is true, then the immediately above
if 
>>>>>>>>> statement needs to be moved outside its enclosing if
- 
>>>>>>>>> otherwise it only gets executed when targets != null.
 We'd 
>>>>>>>>> want this to execute if we found a matching target wouldn't
we?
>>>>>>>> Don't think so? We only want the message going to  one 
>>>>>>>> subscription? I may have misunderstood what you mean!
>>>>>>> Yes - ignore what I said, I had my wires crossed.
>>>>>>>
>>>>>>> Cheers,
>>>>>>> David
>>>>>>>
>>>>>
>>>>>
>>>>> -- 
>>>>> Cheers,
>>>>> David
>>>>>
>>>>> Nuix Pty Ltd
>>>>> Suite 79, 89 Jones St, Ultimo NSW 2007, Australia    Ph: +61 2 9280 
>>>>> 0699
>>>>> Web: http://www.nuix.com                            Fax: +61 2 9212 
>>>>> 6902
>>>>> Index: 
>>>>> activemq-core/src/main/java/org/apache/activemq/broker/region/PrefetchSubscription.java

>>>>>
>>>>> ===================================================================
>>>>> --- 
>>>>> activemq-core/src/main/java/org/apache/activemq/broker/region/PrefetchSubscription.java
   
>>>>> (revision 628917)
>>>>> +++ 
>>>>> activemq-core/src/main/java/org/apache/activemq/broker/region/PrefetchSubscription.java
   
>>>>> (working copy)
>>>>> @@ -160,6 +160,8 @@
>>>>>    public  void acknowledge(final ConnectionContext context,final 
>>>>> MessageAck ack) throws Exception {
>>>>>        // Handle the standard acknowledgment case.
>>>>>        boolean callDispatchMatched = false;
>>>>> +    Queue queue = null;
>>>>> +           synchronized(dispatchLock) {
>>>>>            if (ack.isStandardAck()) {
>>>>>                // Acknowledge all dispatched messages up till the 
>>>>> message id of
>>>>> @@ -223,8 +225,12 @@
>>>>>                                prefetchExtension = Math.max(0,
>>>>>                                        prefetchExtension - (index + 
>>>>> 1));
>>>>>                            }
>>>>> +                if (queue == null)
>>>>> +                {
>>>>> +                queue = (Queue)node.getRegionDestination();
>>>>> +                }
>>>>>                            callDispatchMatched = true;
>>>>> -                            break;
>>>>> +                break;
>>>>>                        }
>>>>>                    }
>>>>>                }
>>>>> @@ -253,6 +259,10 @@
>>>>>                    if 
>>>>> (ack.getLastMessageId().equals(node.getMessageId())) {
>>>>>                        prefetchExtension = Math.max(prefetchExtension,
>>>>>                                index + 1);
>>>>> +                        if (queue == null)
>>>>> +                        {
>>>>> +                            queue = 
>>>>> (Queue)node.getRegionDestination();
>>>>> +                        }
>>>>>                        callDispatchMatched = true;
>>>>>                        break;
>>>>>                    }
>>>>> @@ -279,6 +289,10 @@
>>>>>                    if (inAckRange) {
>>>>>                        node.incrementRedeliveryCounter();
>>>>>                        if (ack.getLastMessageId().equals(messageId))
{
>>>>> +                if (queue == null)
>>>>> +                {
>>>>> +                queue = (Queue)node.getRegionDestination();
>>>>> +                }
>>>>>                            callDispatchMatched = true;
>>>>>                            break;
>>>>>                        }
>>>>> @@ -320,6 +334,10 @@
>>>>>                        if (ack.getLastMessageId().equals(messageId))
{
>>>>>                            prefetchExtension = Math.max(0, 
>>>>> prefetchExtension
>>>>>                                    - (index + 1));
>>>>> +                if (queue == null)
>>>>> +                {
>>>>> +                queue = (Queue)node.getRegionDestination();
>>>>> +                }
>>>>>                            callDispatchMatched = true;
>>>>>                            break;
>>>>>                        }
>>>>> @@ -336,6 +354,9 @@
>>>>>            }
>>>>>        }
>>>>>        if (callDispatchMatched) {
>>>>> +        if (Queue.LAZY_DISPATCH) {
>>>>> +        queue.wakeup();
>>>>> +        }
>>>>>            dispatchPending();
>>>>>        } else {
>>>>>            if (isSlave()) {
>>>>> Index: 
>>>>> activemq-core/src/main/java/org/apache/activemq/broker/region/Queue.java

>>>>>
>>>>> ===================================================================
>>>>> --- 
>>>>> activemq-core/src/main/java/org/apache/activemq/broker/region/Queue.java
   
>>>>> (revision 628917)
>>>>> +++ 
>>>>> activemq-core/src/main/java/org/apache/activemq/broker/region/Queue.java
   
>>>>> (working copy)
>>>>> @@ -75,6 +75,8 @@
>>>>> * @version $Revision: 1.28 $
>>>>> */
>>>>> public class Queue extends BaseDestination implements Task {
>>>>> +    public static final boolean LAZY_DISPATCH =
>>>>> +    
>>>>> Boolean.parseBoolean(System.getProperty("activemq.lazy.dispatch", 
>>>>> "true"));
>>>>>    private final Log log;
>>>>>    private final List<Subscription> consumers = new 
>>>>> ArrayList<Subscription>(50);
>>>>>    private PendingMessageCursor messages;
>>>>> @@ -212,12 +214,12 @@
>>>>>            synchronized (pagedInMessages) {
>>>>>                // Add all the matching messages in the queue to the
>>>>>                // subscription.
>>>>> -
>>>>>                for (Iterator<MessageReference> i = 
>>>>> pagedInMessages.values()
>>>>>                        .iterator(); i.hasNext();) {
>>>>>                    QueueMessageReference node = 
>>>>> (QueueMessageReference) i
>>>>>                            .next();
>>>>> -                    if (!node.isDropped() && !node.isAcked()
&& 
>>>>> (!node.isDropped() ||sub.getConsumerInfo().isBrowser())) {
>>>>> +                    if ((!node.isDropped() || 
>>>>> sub.getConsumerInfo().isBrowser()) && !node.isAcked() &&
>>>>> +            node.getLockOwner() == null) {
>>>>>                        msgContext.setMessageReference(node);
>>>>>                        if (sub.matches(node, msgContext)) {
>>>>>                            sub.add(node);
>>>>> @@ -940,7 +945,11 @@
>>>>>        dispatchLock.lock();
>>>>>        try{
>>>>>
>>>>> -            final int toPageIn = getMaxPageSize() - 
>>>>> pagedInMessages.size();
>>>>> +            int toPageIn = getMaxPageSize() - pagedInMessages.size();
>>>>> +        if (LAZY_DISPATCH) {
>>>>> +        // Only page in the minimum number of messages which can 
>>>>> be dispatched immediately.
>>>>> +        toPageIn = Math.min(getConsumerMessageCountBeforeFull(), 
>>>>> toPageIn);
>>>>> +        }
>>>>>            if ((force || !consumers.isEmpty()) && toPageIn >
0) {
>>>>>                messages.setMaxBatchSize(toPageIn);
>>>>>                int count = 0;
>>>>> @@ -976,12 +985,25 @@
>>>>>        }
>>>>>        return result;
>>>>>    }
>>>>> +
>>>>> +    private int getConsumerMessageCountBeforeFull() throws 
>>>>> Exception {
>>>>> +    int total = 0;
>>>>> +        synchronized (consumers) {
>>>>> +            for (Subscription s : consumers) {
>>>>> +        if (s instanceof PrefetchSubscription) {
>>>>> +            total += ((PrefetchSubscription)s).countBeforeFull();
>>>>> +        }
>>>>> +        }
>>>>> +    }
>>>>> +    return total;
>>>>> +    }
>>>>>
>>>>>    private void doDispatch(List<MessageReference> list) throws

>>>>> Exception {
>>>>>
>>>>>        if (list != null) {
>>>>>            synchronized (consumers) {
>>>>>                for (MessageReference node : list) {
>>>>> +
>>>>>                    Subscription target = null;
>>>>>                    List<Subscription> targets = null;
>>>>>                    for (Subscription s : consumers) {
>>>
>>>
>>> -- 
>>> Cheers,
>>> David
>>>
>>> Nuix Pty Ltd
>>> Suite 79, 89 Jones St, Ultimo NSW 2007, Australia    Ph: +61 2 9280 0699
>>> Web: http://www.nuix.com                            Fax: +61 2 9212 6902
> 
> 


-- 
Cheers,
David

Nuix Pty Ltd
Suite 79, 89 Jones St, Ultimo NSW 2007, Australia    Ph: +61 2 9280 0699
Web: http://www.nuix.com                            Fax: +61 2 9212 6902

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