<div dir="ltr">I think the 4th of the options you proposed would be the best. We don't want to give agents direct access to the agent object or else we will run the risk of breaking extensions all of the time during any kind of reorganization or refactoring. Having a well defined API in between will give us flexibility to move things around. </div><div class="gmail_extra"><br><div class="gmail_quote">On Fri, Sep 25, 2015 at 1:32 AM, <span dir="ltr"><<a href="mailto:thomas.morin@orange.com" target="_blank">thomas.morin@orange.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
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<div>
<p>Hi everyone,<br>
</p>
<p>(TL;DR: we would like an L2 agent extension to be able to call
methods on the agent class, e.g. OVSAgent)<br>
</p>
<p>In the networking-bgpvpn project, we need the reference driver
to interact with the ML2 openvswitch agent with new RPCs to
allow exchanging information with the BGP VPN implementation
running on the compute nodes. We also need the OVS agent to
setup specific things on the OVS bridges for MPLS traffic.</p>
<p>To extend the agent behavior, we currently create a new agent
by mimicking the main() in ovs_neutron_agent.py but instead
of instantiating instantiate OVSAgent, with instantiate a class
that overloads the OVSAgent class with the additional behavior
we need [1] .<br>
</p>
<p>This is really not the ideal way of extending the agent, and we
would prefer using the L2 agent extension framework [2].
</p>
<p>Using the L2 agent extension framework would work, but only
partially: it would easily allos us to register our RPC
consumers, but not to let us access to some
datastructures/methods of the agent that we need to use: setup_entry_for_arp_reply
and local_vlan_map, access to the OVSBridge objects to
manipulate OVS ports.<br>
</p>
<p>I've filled-in an RFE bug to track this issue [5].</p>
<p>We would like something like one of the following:<br>
1) augment the L2 agent extension interface
(AgentCoreResourceExtension) to give access to the agent object
(and thus let the extension call methods of the agent) by giving
the agent as a parameter of the initialize method [4]<br>
2) augment the L2 agent extension interface
(AgentCoreResourceExtension) to give access to the agent object
(and thus let the extension call methods of the agent) by giving
the agent as a parameter of a new setAgent method<br>
3) augment the L2 agent extension interface
(AgentCoreResourceExtension) to give access only to
specific/chosen methods on the agent object, for instance by
giving a dict as a parameter of the initialize method [4], whose
keys would be method names, and values would be pointer to these
methods on the agent object<br>
4) define a new interface with methods to access things inside
the agent, this interface would be implemented by an object
instantiated by the agent, and that the agent would pass to the
extension manager, thus allowing the extension manager to passe
the object to an extension through the initialize method of
AgentCoreResourceExtension [4]<br>
<br>
Any feedback on these ideas...?<br>
Of course any other idea is welcome...<br>
<br>
For the sake of triggering reaction, the question could be
rephrased as: if we submit a change doing (1) above, would it
have a reasonable chance of merging ?<br>
</p>
<p>-Thomas<br>
<br>
[1] <a href="https://github.com/openstack/networking-bgpvpn/blob/master/networking_bgpvpn/neutron/services/service_drivers/bagpipe/ovs_agent/ovs_bagpipe_neutron_agent.py" target="_blank">https://github.com/openstack/networking-bgpvpn/blob/master/networking_bgpvpn/neutron/services/service_drivers/bagpipe/ovs_agent/ovs_bagpipe_neutron_agent.py</a><br>
[2] <a href="https://review.openstack.org/#/c/195439/" target="_blank">https://review.openstack.org/#/c/195439/</a><br>
[3] <a href="https://github.com/openstack/neutron/blob/master/neutron/plugins/ml2/drivers/openvswitch/agent/extension_drivers/qos_driver.py#L30" target="_blank">https://github.com/openstack/neutron/blob/master/neutron/plugins/ml2/drivers/openvswitch/agent/extension_drivers/qos_driver.py#L30</a><br>
[4] <a href="https://github.com/openstack/neutron/blob/master/neutron/agent/l2/agent_extension.py#L28" target="_blank">https://github.com/openstack/neutron/blob/master/neutron/agent/l2/agent_extension.py#L28</a><br>
[5] <a href="https://bugs.launchpad.net/neutron/+bug/1499637" target="_blank">https://bugs.launchpad.net/neutron/+bug/1499637</a><br>
<br>
</p>
</div>
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