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From pollotek <claudio.sant...@gmail.com>
Subject Re: Store and Forward with embedded brokers + stand alone broker
Date Mon, 13 Aug 2012 20:08:22 GMT
Hi torsten,  in-line comments.

On Mon, Aug 13, 2012 at 12:33 AM, Torsten Mielke-2 [via ActiveMQ] <
ml-node+s2283324n4655036h72@n4.nabble.com> wrote:

> Hello,
>
> Some answers in-line.
>
>
> On Aug 11, 2012, at 4:20 AM, pollotek wrote:
>
> > I have this web application that currently connects to a stand alone
> broker
> > to place messages and consumer only nodes pick up and process the
> messages.
> > I want to move this to have embedded brokers on each web app and each
> > consumer and those embedded brokers should forward their messages to a
> stand
> > alone broker that will sit in the middle just like it does today.
> >
> > producer app server -> embedded broker -> stand alone broker -> embedded
> > broker -> consumer app server
> >
> > This will allow messages to be produced and queued up locally without
> > blocking and have the messages forwarded asynchronously.
>
> True but at the expense of a more complex topology. If you have a higher
> number of producers and consumer, you will end up with a fairly huge
> hub-and-spoke broker network topology. Do you really expect your JMS
> clients to be disconnected from the standalone broker that often that you
> want to additionally run with embedded brokers?
>

What would be the implications of a more complex topology? I don't want
messages production calls to block, I read I could use timeouts but if my
call to place a message on the stand alone broker times out I have to
handle the case which complicates my code. If the message gets queued up
locally by the embedded broker my code becomes much simpler.

I also read in the AMQ documentation about the existence of some buffering
mechanism so messages are placed in a local buffer if the stand alone
broker is down but that mechanism is not persistent and I read comments
where embedded broker was the reliable way to implement this functionality.


>
>
>
> > As I understand the
> > only thing to do here is to declare the embedded brokers on both app
> servers
> > and point their network connectors to the stand alone broker. Messages
> are
> > supposed to be stored in the embedded broker and if there are
> subscribers to
> > the queue on the stand alone broker side messages will be forwarded.
>
> Correct. However the network connector from your consumers embedded broker
> to the standalone broker needs to be duplex, as otherwise msgs can only
> from from that embedded broker to the standalone broker.
>
> >
> > So I configured my embedded brokers with these parameters (this is the
> same
> > configuration on both, consumers and producers) :
> >
> >        <amq:transportConnectors>
> >            <amq:transportConnector uri="vm://localhost?async=true" />
> >        </amq:transportConnectors>
> >
> >        <amq:networkConnectors>
> >            <amq:networkConnector
> > name="connection_to_nob-${activemq.brokerid}"
> >
> >
> uri="static:failover:(tcp://broker01:61616,tcp://broker02:61616)?randomize=false&amp;maxReconnectAttempts=0"/>
>
> >        </amq:networkConnectors>
>
> Add duplex=true to the network connectors of your consumer embedded
> brokers as mentioned above.
>
>
> > The stand alone broker of course is configured to receive connections on
> > 61616. I start up my application and make sure with JMX all consumers
> and
> > producers are connected to the same broker (Master-slave shared file
> system)
> > and everything looks ok so far. I create some messages for queues I have
> > consumers for declared in the consumer side only.
>
> To get up and running and eliminate possible errors, perhaps try without
> master/slave first.
> >
> > I point my producer and consumer app servers to connect to
> vm://localhost. I
> > never see a single message leave the embedded broker on the producers
> side.
> > I can see with JMX the stand alone broker doesn't create the queues
> where my
> > process is placing new messages.
>
> Could be done to the fact that some of your network connectors needs to be
> duplex.
> For testing try to connect with a consumer to the standalone broker first
> and see if msgs get passed from the producer's embedded broker to the
> standalone broker and to your directly connected consumer.
> If they do, then your producer side configuration is correct. Then check
> the consumers config.
>

I actually ran this test already successfully with embedded brokers on the
producer side and direct connections to the stand alone broker on the
consumer side.


>
> >
> > As I understand from what I read I don't need to specifically create the
> > queues to get messages forwarded to in the stand alone broker, they're
> > supposed to be automatically created.
>
> Correct, destinations get created automatically by the brokers once a
> producer or consumer is connected.
>
>
> > I don't have anything special on my
> > stand alone broker other than this destination Policy which I also have
> on
> > the embedded brokers:
> >
> > <destinationPolicy>
> >            <policyMap>
> >                <policyEntries>
> >
> >                    <policyEntry queue=">">
> >                        <deadLetterStrategy>
> >
> >                            <individualDeadLetterStrategy
> queuePrefix="DLQ."
> > useQueueForQueueMessages="true" />
> >                        </deadLetterStrategy>
> >                    </policyEntry>
> >                </policyEntries>
> >            </policyMap>
> >        </destinationPolicy>
> >
>
> That config is fine and would not cause your problem.
> See my above points and also verify that you did not disable support for
> advisory messages explicitly in your broker configurations. These are
> needed in a broker network to share information about connected JMS
> clients.
> http://activemq.apache.org/advisory-message.html
>
>
>
> > I'm running 5.6.0 on brokers and clients with Java 1.6.0.14 on Linux,
> > embedded and stand alone brokers are persistent.
> >
> > Any ideas of what I am missing?
> >
>
>
> Hope this helps a bit.
>
>
> Torsten Mielke
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>
>
>
>
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I won't be able to run this test for a few days. I'll let you know the
results.

Thanks for the quick and detailed response!

Claudio




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