Re: Consumers being created under load

[Tim Bain <tb...@alumni.duke.edu>]

Is this on a standalone broker, or are you running a network of brokers?
Might these consumers be the ones for one broker in a network of brokers to
pull messages from another?

Tim

On Thu, Apr 30, 2020, 1:32 PM bstrange <bs...@smc3.com> wrote:

> I'm running ActiveMQ 5.11.1 and have two consumers on a queue. If something
> causes the load on the server to spike additional
> phantom/ghost/auto-created
> consumers are created by activemq. These consumers are named the same as
> the
> host when none of the other consumers exist on this host. Does anyone know
> what these are for, what they do, or have any information about them at
> all?
> In the attached image the bottom two are the normal consumers. The top one
> is the auto created consumer.
>
> <
> http://activemq.2283324.n4.nabble.com/file/t379917/amq-created-consumer.png>
>
>
> I've been able to duplicate the behavior on another server even with zero
> consumers running. In this case when the server load spikes I've seen 3 new
> consumers created. They stay listed until the server load drops back to
> normal.  Any ideas?
>
>
>
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Re: Consumers being created under load

[Tim Bain <tb...@alumni.duke.edu>]

That makes sense. Thanks for sharing the resolution to the problem.

Tim

On Thu, May 7, 2020, 8:23 AM bstrange <bs...@smc3.com> wrote:

> I've finally figured out what was causing this. Viewing the contents of a
> queue by clicking the queue name in the browser interface will spawn a
> consumer to view all of that data. The more messages in the queue the
> longer
> the cpu spike will last. These consumers don't actually consume the
> messages; it appears to be more of an indexing or listing of the queue
> contents. Once they have all been listed the consumer goes away and the cpu
> load drops back to normal.
>
>
>
> --
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>

Re: Consumers being created under load

[bstrange <bs...@smc3.com>]

I've finally figured out what was causing this. Viewing the contents of a
queue by clicking the queue name in the browser interface will spawn a
consumer to view all of that data. The more messages in the queue the longer
the cpu spike will last. These consumers don't actually consume the
messages; it appears to be more of an indexing or listing of the queue
contents. Once they have all been listed the consumer goes away and the cpu
load drops back to normal.



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Re: Consumers being created under load

[Tim Bain <tb...@alumni.duke.edu>]

If these are consumers on a queue, are they consuming the queue's messages
such that your real consumers don't get all of them? Or are all of the
messages still on the queue despite these consumers having received a
million messages (per your screenshot in your original message)?

How often do these consumers appear, and how long do they last? And by
"load", I assume you mean high CPU? Or do you mean some other measure like
disk or network?

What settings are you using for message expiration? Are you using scheduled
messages? Do you have any embedded Camel routes? Are there any meaningful
advisory messages produced during or immediately after the period of load?

I don't have any good ideas for what these consumers are, so I'm guessing
at things that might possibly make use of a short-lived consumer in the
hopes that one of them turns out to be related to what you're seeing. But
I'm grasping at straws, so this might end with "I have no idea, but maybe
try upgrading to the latest 5.15.x version and see if it's still a problem
there."

The only other thing I notice is that the unexpected consumer uses a
prefetch buffer size of 500 rather than the standard 1000. But I'm not sure
why that value would be used instead of the default.

Tim

On Tue, May 5, 2020, 8:57 AM bstrange <bs...@smc3.com> wrote:

> The high load could be caused by the phantom consumers and not the other
> way
> around. I've only been able to duplicate the issue once in testing.
>
>
>
> --
> Sent from:
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>

Re: Consumers being created under load

[bstrange <bs...@smc3.com>]

The high load could be caused by the phantom consumers and not the other way
around. I've only been able to duplicate the issue once in testing.



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Re: Consumers being created under load

[bstrange <bs...@smc3.com>]

It's a standalone broker. We don't have any networked brokers. These
consumers aren't any we created. They're created on their own and go away on
their own.



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