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From Christian Posta <christian.po...@gmail.com>
Subject Re: Understanding memoryUsage (once again!)
Date Wed, 21 Nov 2012 16:28:08 GMT
Can you please try on 5.7?
I just tried a test, and if there are no consumers to the queue then the
memory usage will stay at 0%. The message will not be retained, ie, it will
be put into the store and kept there. If I add a consumer, and not try to
consume, the message will be kept around in memory up to the cursor high
watermark (70 by default).

As I add more queues the same behavior as described above will happen. If I
attach consumers to the queues without consuming them (so no messages are
consumed), then messages are kept in the cursor up to the high-water
mark... note.. the high-water mark is relative to the Destination/Cursor's
MemoryUsage, not the global memory usage.

If I continue adding queues, and with producer flow control set to false, I
too will see the *Global* memory usage go much higher than 100%. This is
not surprising though, because as I understand, these usage memory objects
are really just counters. They don't enforce anything. When coupled with
producer flow control, they can be used to determine when to enable PFC. If
PFC is false, it's up to the cursor to determine when to flush out to disk.
But each destination/cursor will have it's own system usage (with the
global as the parent).

Hope this helps. Can you please try with 5.7 and give us a report back?
Thanks,
Christian



On Fri, Nov 16, 2012 at 11:38 AM, Juan Nin <juanin@gmail.com> wrote:

> nope, adding a 3rd queue the 3rd one also gets this same value, so even if
> it's the memory usage of the queue it's anyway going beyond..
>
>
> On Fri, Nov 16, 2012 at 4:32 PM, Juan Nin <juanin@gmail.com> wrote:
>
> > Might it be just a bug on how the MemoryPercentUsage is calculated?
> >
> > If I connect via JMX using console, I can see the MemoryPercentUsage as
> > 112 right now.
> > If I go to each of the 2 queues on them I see CursorMemoryUsage with
> value
> > 29360604, which would be 28mb each, summing a total of 56mb (just a bit
> > more than the specified memoryUsage of 50mb).
> >
> > Not sure I'm interpreting these values correctly though, first time I
> > access it via jconsole...
> >
> >
> > On Fri, Nov 16, 2012 at 4:07 PM, Juan Nin <juanin@gmail.com> wrote:
> >
> >> On that config there's a 40mb memoryLimit per queue, but also tested it
> >> without it with same results.
> >>
> >>
> >> On Fri, Nov 16, 2012 at 4:05 PM, Juan Nin <juanin@gmail.com> wrote:
> >>
> >>> Hi Torsten!
> >>>
> >>> I'm using ActiveMQ 5.3.2, but also tested it on 5.7.0 with the same
> >>> results...
> >>> This is my 5.3.2 config:
> >>>
> >>> <beans
> >>>   xmlns="http://www.springframework.org/schema/beans"
> >>>   xmlns:amq="http://activemq.apache.org/schema/core"
> >>>   xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
> >>>   xsi:schemaLocation="http://www.springframework.org/schema/beans
> >>> http://www.springframework.org/schema/beans/spring-beans-2.0.xsd
> >>>   http://activemq.apache.org/schema/core
> >>> http://activemq.apache.org/schema/core/activemq-core.xsd">
> >>>
> >>>     <bean
> >>>
> class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">
> >>>         <property name="locations">
> >>>
> >>> <value>file:${activemq.base}/conf/credentials.properties</value>
> >>>         </property>
> >>>     </bean>
> >>>
> >>>     <broker xmlns="http://activemq.apache.org/schema/core"
> >>> brokerName="localhost" dataDirectory="${activemq.base}/data"
> >>> destroyApplicationContextOnStop="true" advisorySupport="false">
> >>>
> >>>         <destinationPolicy>
> >>>             <policyMap>
> >>>                 <policyEntries>
> >>>                     <policyEntry topic=">" producerFlowControl="true"
> >>> memoryLimit="5mb">
> >>>                         <pendingSubscriberPolicy>
> >>>                             <vmCursor />
> >>>                         </pendingSubscriberPolicy>
> >>>                     </policyEntry>
> >>>                     <policyEntry queue=">" producerFlowControl="false"
> >>> optimizedDispatch="true" memoryLimit="40mb">
> >>>                 <deadLetterStrategy>
> >>>                             <individualDeadLetterStrategy
> >>> queuePrefix="DLQ." useQueueForQueueMessages="true" />
> >>>                         </deadLetterStrategy>
> >>>                     </policyEntry>
> >>>                 </policyEntries>
> >>>             </policyMap>
> >>>         </destinationPolicy>
> >>>
> >>>         <managementContext>
> >>>             <managementContext connectorPort="2011"/>
> >>>         </managementContext>
> >>>
> >>>         <persistenceAdapter>
> >>>             <kahaDB directory="${activemq.base}/data/kahadb"
> >>> enableJournalDiskSyncs="false" indexWriteBatchSize="10000"
> >>> indexCacheSize="1000"/>
> >>>         </persistenceAdapter>
> >>>
> >>>         <systemUsage>
> >>>             <systemUsage>
> >>>               <memoryUsage>
> >>>                     <memoryUsage limit="50 mb"/>
> >>>                  </memoryUsage>
> >>>                 <storeUsage>
> >>>                     <storeUsage limit="1 gb" name="foo"/>
> >>>                 </storeUsage>
> >>>                 <tempUsage>
> >>>                     <tempUsage limit="3 gb"/>
> >>>                 </tempUsage>
> >>>             </systemUsage>
> >>>         </systemUsage>
> >>>
> >>>         <transportConnectors>
> >>>             <transportConnector name="openwire" uri="tcp://
> 0.0.0.0:61616
> >>> "/>
> >>>     <transportConnector name="stomp" uri="stomp://0.0.0.0:61613"/>
> >>>         </transportConnectors>
> >>>
> >>>     </broker>
> >>>
> >>>     <import resource="jetty.xml"/>
> >>>
> >>> </beans>
> >>>
> >>>
> >>> Using just a simple PHP script with Stomp for feeding the queues
> >>> (running it twice with different queue name):
> >>>
> >>> <?php
> >>>
> >>> require_once("Stomp.php");
> >>>
> >>> $amq = new Stomp("tcp://localhost:61613");
> >>> $amq->connect();
> >>>
> >>> for($i=1; $i <= 100000; $i++)
> >>> {
> >>> if($i%1000 == 0)
> >>> {
> >>>  echo "\nmsg #: $i";
> >>> }
> >>> $amq->send("/queue/test", "this is test message # $i"
> >>> ,array('persistent' => 'true'));
> >>> }
> >>>
> >>> $amq->disconnect();
> >>>
> >>> ?>
> >>>
> >>>
> >>>
> >>> On Fri, Nov 16, 2012 at 3:47 PM, Torsten Mielke <
> torsten@fusesource.com>wrote:
> >>>
> >>>> Hello,
> >>>>
> >>>> See in-line response.
> >>>>
> >>>> On Nov 16, 2012, at 6:29 PM, Juan Nin wrote:
> >>>>
> >>>> > Hi!
> >>>> >
> >>>> > After some heavy digging about Producer Flow control and the
> >>>> systemUsage
> >>>> > properties a couple of years ago, I thought I quite understood
it.
> >>>> > But yesterday I found that one of my configs was not behaving
> exactly
> >>>> as I
> >>>> > expected, so started doing some tests, and I see certain behaviours
> >>>> which
> >>>> > don't seem to match what the docs and posts that I find on the
list
> or
> >>>> > other forums say.
> >>>> >
> >>>> > "storeUsage" is perfectly clear, it's the max space that persistent
> >>>> > messages can use to be stored in disk.
> >>>> > "tempUsage"" applies to file cursors on non-persistent messages,
so
> >>>> as to
> >>>> > flush to disk if memory limits are reached (I don't care much about
> >>>> this
> >>>> > one anyway, I always use persistent messages).
> >>>>
> >>>> Correct.
> >>>>
> >>>> >
> >>>> > Now, according to most posts, memoryUsage would be the maximum
> memory
> >>>> that
> >>>> > the broker would be available to use.
> >>>> > On this post:
> >>>> >
> >>>>
> http://stackoverflow.com/questions/7646057/activemq-destinationpolicy-and-systemusage-configurationit
> >>>> > says that "memoryUsage corresponds to the amount of memory that's
> >>>> > assigned to the in-memory store".
> >>>>
> >>>> Correct.
> >>>>
> >>>> >
> >>>> > For example, on my tests using the following config (only showing
> >>>> relevant
> >>>> > parts):
> >>>> >
> >>>> > <policyEntry queue=">" producerFlowControl="false"
> >>>> optimizedDispatch="true">
> >>>> >    <deadLetterStrategy>
> >>>> >        <individualDeadLetterStrategy queuePrefix="DLQ."
> >>>> > useQueueForQueueMessages="true" />
> >>>> >    </deadLetterStrategy>
> >>>> > </policyEntry>
> >>>> >
> >>>> > <systemUsage>
> >>>> >    <systemUsage>
> >>>> >        <memoryUsage>
> >>>> >            <memoryUsage limit="100 mb"/>
> >>>> >        </memoryUsage>
> >>>> >        <storeUsage>
> >>>> >            <storeUsage limit="1 gb" name="foo"/>
> >>>> >        </storeUsage>
> >>>> >        <tempUsage>
> >>>> >            <tempUsage limit="3 gb"/>
> >>>> >        </tempUsage>
> >>>> >    </systemUsage>
> >>>> > </systemUsage>
> >>>> >
> >>>> > With that config I would expect the broker to use 100 mb of maximum
> >>>> memory
> >>>> > among all queues. So it could maybe use 30mb in one queue and 70mb
> in
> >>>> > second queue.
> >>>> >
> >>>> >
> >>>> > 1) What I'm seeing is that if I start feeding a queue without
> >>>> consuming it,
> >>>> > the "Memory percent used" grows up to 70%, after that it doesn't
> grow
> >>>> > anymore.
> >>>> > What is it doing exactly there? The first 70% is stored in memory
> >>>> (apart
> >>>> > from disk since it's persistent), and all the rest that continues
> >>>> being fed
> >>>> > goes just to disk?
> >>>>
> >>>> This behavior is correct. For queues the default cursor is store
> >>>> cursor. It keeps any newly arrived msgs in memory as long as it does
> not
> >>>> reach the configured memory limit (either configured on the queue per
> >>>> destination or globally in memoryUsage settings).
> >>>> Once the cursor reaches 70% of the configured limit (in your case of
> >>>> the memoryUsage limit since you don't specify a per-destination
> limit), it
> >>>> will not keep any more messages in memory.
> >>>> Instead it will reload these messages from the store when its time to
> >>>> dispatch them. The broker anyway persists any msgs it receives before
> >>>> passing on to the cursor.
> >>>> This limit of 70% can be configured and raised to e..g 100%.
> >>>> This behavior is kind of an optimization. That way you run less often
> >>>> into producer-flow-control.
> >>>> As long as the persistence store is not running full, there is no need
> >>>> to block producers, since the cursor can also load the messages from
> the
> >>>> store and does not necessarily have to keep them in memory.
> >>>> If you configure the vmQueueCursor, then the behavior is different.
> >>>> This cursor will not be able to load msgs to the store but needs to
> keep
> >>>> them all in memory. The vmQueueCursor used to be the default cursor
in
> >>>> older version of AMQ.
> >>>>
> >>>> Also note that topic msgs and non-persistent queue messages are not
> >>>> handled by the store cursor. These msgs are held in memory and if
> memory
> >>>> runs low, get swapped out to temp storage.
> >>>>
> >>>> > 2) If then I start feeding a 2nd queue, "Memory percent used"
> >>>> continues
> >>>> > growing until it reaches 140%. So it looks like memoryUsage does
not
> >>>> apply
> >>>> > globally, but on a per queue basis?
> >>>>
> >>>> What version of AMQ do you use? The sum of the memory usage of all
> >>>> queues should not go any higher than the configured memoryUsage
> limit. If
> >>>> you're not on 5.5.1 or higher releases, then I suggest to upgrade.
> >>>>
> >>>> > Using memoryLimit on the queue's policyEntry gives more control
over
> >>>> this,
> >>>> > but it's just a variation, "Memory percent used" can grow more
than
> >>>> 100%
> >>>> > anyway.
> >>>>
> >>>> With the default store cursor this should not be the case from what
I
> >>>> know.
> >>>>
> >>>>
> >>>> >
> >>>> > 3) If #2 is true, then how would I prevent the broker from running
> >>>> out of
> >>>> > memory in case queues would continue to be created?
> >>>>
> >>>> Just like above comment. I would expect the brokers MemoryPercentUsage
> >>>> won't grow over 100% and the destinations MemoryPercentUsage remains
> fairly
> >>>> much at 70%.
> >>>> Not sure why you would see a different behavior? Using an old version
> >>>> of AMQ perhaps? Or explicitly configuring for the vmQueueCursor?
> >>>> Could you perhaps also test with
> >>>>
> >>>> >
> >>>> >
> >>>> > Maybe I'm misunderstanding and some of these settings make no sense
> >>>> when
> >>>> > producerFlowControl is disabled?
> >>>> >
> >>>> > Thanks in advance.
> >>>> >
> >>>> > Juan
> >>>>
> >>>>
> >>>> Regards,
> >>>>
> >>>> Torsten Mielke
> >>>> torsten@fusesource.com
> >>>> tmielke.blogspot.com
> >>>>
> >>>>
> >>>>
> >>>>
> >>>>
> >>>
> >>
> >
>



-- 
*Christian Posta*
http://www.christianposta.com/blog
twitter: @christianposta

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