<div dir="ltr"><br><div class="gmail_extra"><br><div class="gmail_quote">On 23 April 2015 at 01:30, Armando M. <span dir="ltr"><<a href="mailto:armamig@gmail.com" target="_blank">armamig@gmail.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-color:rgb(204,204,204);border-left-style:solid;padding-left:1ex"><div dir="ltr"><div class="gmail_extra"><br><div class="gmail_quote"><span class="">On 22 April 2015 at 06:02, Miguel Angel Ajo Pelayo <span dir="ltr"><<a href="mailto:mangelajo@redhat.com" target="_blank">mangelajo@redhat.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-color:rgb(204,204,204);border-left-style:solid;padding-left:1ex"><br>
Hi everybody,<br>
<br>
In the latest QoS meeting, one of the topics was a discussion about how to implement<br>
QoS [1] either as in core, or as a service plugin, in, or out-tree.<br></blockquote></span></div></div></div></blockquote><div><br></div><div>It is really promising that after only two meetings the team is already split! I cannot wait for the API discussion to start ;)</div><div> </div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-color:rgb(204,204,204);border-left-style:solid;padding-left:1ex"><div dir="ltr"><div class="gmail_extra"><div class="gmail_quote"><span class=""><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-color:rgb(204,204,204);border-left-style:solid;padding-left:1ex"></blockquote><div><br></div></span>My apologies if I was unable to join, the meeting clashed with another one I was supposed to attend.<span class=""><div> <br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-color:rgb(204,204,204);border-left-style:solid;padding-left:1ex">
<br>
It’s my feeling, and Mathieu’s that it looks more like a core feature, as we’re talking of<br>
port properties that we define at high level, and most plugins (QoS capable) may want<br>
to implement at dataplane/controlplane level, and also that it’s something requiring a good<br>
amount of review.<br></blockquote></span></div></div></div></blockquote><div><br></div><div>"Core" is a term which is recently being abused in Neutron... However, I think you mean that it is a feature fairly entangled with the L2 mechanisms that deserves being integrated in what is today the "core" plugin and in the OVS/LB agents. To this aim I think it's good to make a distinction between the management plane and the control plane implementation.</div><div><br></div><div>At the management plane you have a few choices:</div><div>- yet another mixin, so that any plugin can add it and quickly support the API extension at the mgmt layer. I believe we're fairly certain everybody understands mixins are not sustainable anymore and I'm hopeful you are not considering this route.</div><div>- a service plugin - as suggested by some proposers. The service plugin is fairly easy to implement, and now Armando has provided you with a mechanism to register for callbacks for events in other plugins. This should make the implementation fairly straightforward. This also enables other plugins to implement QoS support.</div><div>- a ML2 mechanism driver + a ML2 extension driver. From an architectural perspective this would be the preferred solution for a ML2 implementation, but at the same time will not provide management level support for non-ML2 plugins.</div><div> </div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-color:rgb(204,204,204);border-left-style:solid;padding-left:1ex"><div dir="ltr"><div class="gmail_extra"><div class="gmail_quote"><span class=""><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-color:rgb(204,204,204);border-left-style:solid;padding-left:1ex">
<br>
<br>
In the other hand Irena and Sean were more concerned about having a good separation<br>
of concerns (I agree actually with that part), and being able to do quicker iterations on a<br>
separate stackforge repo.<br></blockquote></span></div></div></div></blockquote><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-color:rgb(204,204,204);border-left-style:solid;padding-left:1ex"><div dir="ltr"><div class="gmail_extra"><div class="gmail_quote"><span class=""><div><br></div></span><div>Perhaps we're trying to address the issue at the wrong time. Once a reasonable agreement has been reached on the data model, and the API, whether we're going with a service plugin or core etc should be an implementation detail. I think the crux of the matter is the data plane integration. From a management and control standpoint it should be fairly trivial to expose/implement the API and business logic via a service plugin and, and some of you suggested, integrate with the core via callbacks.</div><div><br></div><div>However, I am pretty sure there will be preliminary work necessary to integrate the server with the agent fabric (when there is one) so that is no longer a pain. Extending what the agent can do the way we did so far (e.g. by adding extra payloads/messages, mixin etc) is not sustainable, and incredibly brittle.</div></div></div></div></blockquote><div><br></div><div>In my opinion the interesting part for an architectural decision here is the control plane support for the reference implementation.</div><div>Adding more stuff to the OVS/LB agents might lead to an increase in technical debt. On the other hand, adding a new QoS agent might lead to further complexity - another loose bit to keep in sync with the rest, and operators usually are not happy about having to manage the lifecycle of another independent component. And as Armando say, you also need to consider what changes you need to the RPC interface. </div><div><br></div><div>Without that information it is hard to make a call, and therefore I agree with Armando that there are not yet enough elements to make a decision - let's wait at least for a high level view of system architecture.</div><div><br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-color:rgb(204,204,204);border-left-style:solid;padding-left:1ex"><div dir="ltr"><div class="gmail_extra"><div class="gmail_quote"><span class=""><div><br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-color:rgb(204,204,204);border-left-style:solid;padding-left:1ex">
<br>
Since we didn’t seem to find an agreement, and I’m probably missing some details,<br>
I’d like to loop in our core developers and PTL to provide an opinion on this.<br></blockquote></span></div></div></div></blockquote><div><br></div><div>Core developers and the PTL do not necessarily have a better opinion... instead in many cases they have a worse one!</div><div>By the way, if you go the stackforge route, then you can apply for becoming an openstack project and one of you can become PTL! Isn't that wonderful? Who doesn't want to be PTL these days?</div><div><br></div><div> </div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-color:rgb(204,204,204);border-left-style:solid;padding-left:1ex"><div dir="ltr"><div class="gmail_extra"><div class="gmail_quote"><span class=""><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-color:rgb(204,204,204);border-left-style:solid;padding-left:1ex">
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[1] <a href="http://eavesdrop.openstack.org/meetings/neutron_qos/2015/neutron_qos.2015-04-21-14.03.log.html#l-192" target="_blank">http://eavesdrop.openstack.org/meetings/neutron_qos/2015/neutron_qos.2015-04-21-14.03.log.html#l-192</a><br>
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Thanks for your patience,<br>
Miguel Angel Ajo<br>
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