Open Stack

On 22/05/15 15:34 -0400, Zane Bitter wrote:
>On 22/05/15 11:48, Amrith Kumar wrote:
>>I’m posting this to the mailing list to summarize my notes from a
>>meeting at 5pm yesterday at Summit relative to Zaqar and lightweight
>>multi-tenant messaging and how it may be applicable to a number of projects.
>>
>>I’ll begin by saying these are not ‘minutes’ of a meeting, merely my
>>notes and observations after the meeting and how they relate
>>specifically to Trove. I don’t claim to speak for Trove, other
>>contributors to Trove, other projects who were at the meeting, for
>>zaqar, etc., etc.,
>>
>>After the meeting I think I have a slightly better understanding of what
>>Zaqar is but I am still not entirely sure. As best as I can tell, it is
>>a lightweight, keystone authenticated, multi-tenant messaging system.
>
>I'm not sure what 'lightweight' means in this context. I'd describe it 
>as a keystone-authenticated multi-tenant reliable messaging system a 
>la Amazon SQS.

This is the way we've been describing it.
>
>>I
>>am still a little troubled that of the many people in the room who were
>>knowledgeable of zaqar, there appeared to be some disagreement on how
>>best to describe or explain the project.
>
>I don't think there's any disagreement. It just seems to be hard to 
>explain to people, because everyone instinctively wants to compare it 
>to Rabbit, which is a completely different thing with completely 
>different use cases. IMHO part of the problem has been that folks have 
>been reluctant to name SQS specifically, and so we end up talking 
>elliptically.

+1

>
>>I learned that users of zaqar can authenticate with keystone and then
>>interact with zaqar, and pass messages using it. I learned also that
>>zaqar is spelt with a ‘q’ that is not followed by a ‘u’. i.e. it isn’t
>>zaquar as I had thought it was.
>>
>>It became clear that the underlying transport in zaqar is not based on
>>an existing AMQP service, rather zaqar is a “from the ground up”
>>implementation. This scares me (a lot).
>
>Yes, literally every person who has ever heard of Zaqar complains 
>about this and it's getting a little boring. It's irrelevant because 
>Zaqar is not a replacement for AMQP, it's a replacement for SQS.

Again +1

>
>>I gather there is currently no oslo.messaging integration with zaqar;
>
>Right, Zaqar has never been intended as a replacement for Rabbit in 
>Oslo messaging.

This is probably the main reason why there's no driver for Zaqar in
oslo.messaging. That is, to prevent people from actually using Zaqar
as a message bus in openstack.

>
>(Although that could be an interesting idea, it's another discussion 
>altogether.)
>
>>for Trove to use zaqar we would have to either (a) abandon
>>oslo.messaging and use zaqar, or (b) build in smarts within Trove to
>>determine at run time whether we are using zaqar or o.m and implement
>>code in Trove to handle the differences between them if any.
>>
>>It wasn’t clear to me after the meeting what differences there may be
>>with Trove; one which was alluded to was the inability to do a
>>synchronous (call()) style message and the statement was that this was
>>something that “could be built into a driver”.
>
>Where Zaqar really provides the biggest benefit is sending the message 
>from the cloud to the user/application (since it can be authenticated 
>by Keystone). IMHO the ideal scenario would be that messages from 
>Trove (or whatever) to the VM would go over Zaqar, and for messages in 
>the other direction would just go straight to the Trove (or whatever) 
>API. The problem is that Keystone's authorisation capabilities are not 
>sufficient to handle this at the moment. One thing that should be 
>possible in a shorter time-frame is a pre-signed URL for a Zaqar queue 
>as a return path.

++

>
>>It wasn’t clear to me what scale zaqar has been run at and whether
>>anyone has in fact deployed and run zaqar at scale, and whether it has
>>been battle hardened the way a service like RabbitMQ has. While I hear
>>from many that RabbitMQ is a nightmare to scale and manage, I realize
>>that it does in fact have a long history of deployments at scale.
>
>I believe that Rackspace deployed it?

And Catalyst

>
>>We discussed some of the assumptions being made in the conversation
>>relative to the security of the various parties to the communication on
>>the existing rabbit message queue and at the conclusion of the meeting I
>>believe we left things as below.
>>
>>(a)Zaqar would be more appealing if it had a simple oslo.messaging
>>driver and an easier path to integration by client projects like Trove.
>>The rip-and-replace option put a certain damper on the enthusiasm
>
>So the key point here is that Trove regards the VM running the 
>database and the Trove agent as within its own security perimeter. 
>(Whether that's appropriate is another debate, but it's up to the 
>Trove contributors to decide.) In this case, the ability to 
>authenticate to the queue using Keystone provides no real value, so 
>this isn't really a use case that requires Zaqar.
>
>The same is not true for other projects, like Heat, Murano and Sahara. 
>Whenever the agent is outside the security perimeter, we need an 
>authenticated, metered, multi-tenant access method.

Correct. When we started talking about integrating Trove and Zaqar was
under the assumption that Trove VMs to be out of Tove's security
perimeter. The Trove team seems to disagree with this assumption,
although there are some OPs that disagree with Trove's team.

>
>>(b)Even with an o.m integration, the incremental benefits that zaqar
>>brought were diminished by the fact that one would still have to operate
>>an AMQP (RabbitMQ) service for the rest of the infrastructure message
>>passing needs unless and until all projects decide to abandon RabbitMQ
>>in favor of zaqar
>
>This is not at all what was being suggested.
>
>Murano, for example, is running a separate RabbitMQ service to talk to 
>its agent on machines that are very much controlled by the user. 
>That's the kind of thing that needs to be replaced by a multi-tenant 
>service. The session was organised because it was assumed that Trove 
>is in the same boat, but it appears that Trove developers don't 
>consider that it is.

++

>
>>(c)At this time it is likely that there is no net benefit to a project
>>like Trove in integrating with zaqar given that the upside is likely
>>limited, the downside(s) that we know of are significant, and there is a
>>significant unknown risk.
>
>I agree that in that in the case of Trove specifically, there's no 
>reason to change unless and until the decision about the location of 
>the security boundary is reconsidered.

Thanks Amrith for your notes and to you, Zane, for replying with so
precise answers to Amrith's email. Unless the perception of what the
Trove VM's boundaries are changes, I agree there's no much point in
dedicating time to this integration.

>>My thanks to the folks from zaqar for having the session, I certainly
>>learnt a lot more about the project, and about openstack.

Thank you all for attending and sharing such detailed information,
Flavio

>>
>>Let me conclude where I began, by saying the preceding is not a ‘minutes
>>of the meeting’, merely my notes from the meeting.
>>
>>Thanks,
>>
>>-amrith
>>
>>
>>
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>
>
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-- 
@flaper87
Flavio Percoco
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