From bd23545778016827e7f520488c224a7943b59310 Mon Sep 17 00:00:00 2001 From: Yang Youseok Date: Tue, 18 Dec 2018 01:21:05 +0900 Subject: [PATCH] Registering RouterInfo by L3 extention API Currently, most plugin implementations releated L3 override the L3NatAgent class itself for their own logic since there is no proper interface to extend RouterInfo class. This adds unnecessary complexity for developers who just want to extend agent mechanism instead of whole RPC related to L3 functinalities. This spec introduces RouterFactory class which acts on the factory for creating RouterInfo class, and add new l3 extension API which enable to dynamically add RouterInfo to the factory. Now plugin developers can use new extension API for their own specific router. Change-Id: Ic3486830e449f6ee8dbe19db614179b2077bcf7b Related-Bug: #1804634 Implements: blueprint router-factory-with-l3-extension --- .../router-factory-with-l3-extension.rst | 124 ++++++++++++++++++ 1 file changed, 124 insertions(+) create mode 100644 specs/stein/router-factory-with-l3-extension.rst diff --git a/specs/stein/router-factory-with-l3-extension.rst b/specs/stein/router-factory-with-l3-extension.rst new file mode 100644 index 000000000..826e22b32 --- /dev/null +++ b/specs/stein/router-factory-with-l3-extension.rst @@ -0,0 +1,124 @@ +.. + This work is licensed under a Creative Commons Attribution 3.0 Unported + License. + + http://creativecommons.org/licenses/by/3.0/legalcode + +========================================== +Registering RouterInfo by L3 extension API +========================================== + +Launchpad blueprint: +https://blueprints.launchpad.net/neutron/+spec/router-factory-with-l3-extension + +Currently, most plugin implementations related to L3 override the *L3NATAgent* +class itself for their own logic since there is no proper interface to +extend the *RouterInfo* class. This adds unnecessary complexity for developers +who just want to extend the agent mechanism instead of the whole RPC related +to L3 functionalities. + +This spec introduces the *RouterFactory* class which acts on the factory for +creating the *RouterInfo* class, and adds a new parameter to the L3 agent +extension API which enables it to dynamically register *RouterInfo* to the +factory. Now plugin developers can use the new extension API for their own +specific router. + + +Problem Description +=================== + +Current L3 agent implementation in Neutron consists of two parts in general. +One is to implement an RPC Plugin API from Neutron server, and the other is to +create ports, namespaces, and iptables rules using the data obtained from the +RPC API on the server. To be more specific, the former is the *L3NATAgent* +class and the latter is the *RouterInfo* class. + +The problem is that the two parts mentioned are now tightly coupled which means +there is no clear way to extend each part individually. A lot of projects +related to Neutron called networking-* [1]_, [2]_, [3]_ are making new L3 +agent classes on their own by extending the *L3NATAgent* class even though +they did not modify the RPC mechanism but only changed the *RouterInfo* +mechanism running on their server. + +Also, the current *RouterInfo* class does not have an abstract interface which +makes it harder to extend the class for plugin developers. They have to find +what functions and variables in *RouterInfo* are externally used in the L3 +agent to extend the *RouterInfo* behaviors. + + +Proposed Change +=============== + +Today, *RouterInfo* is extended in several ways according to specific router +features such as distributed, ha, and distributed + ha. This document proposes +changing the L3 agent to have a new class called ``RouterFactory`` which has +several pre-registered classes to extend the *RouterInfo* class with certain +features. When it comes to creating an actual *RouterInfo* instance, the L3 +agent create a new instance from the ``RouterFactory`` following the features +of the router. There is no functional change for existing code. + +*L3AgentExtensionAPI* now has a new parameter ``router_factory`` and a new +function ``register_router``. A new abstract class called ``BaseRouterInfo`` +will be added. It will declare interfaces that are currently used externally. + +An L3 extension can register their own *RouterInfo* class which implements +``BaseRouterInfo`` using the ``register_router`` API which has two parameters. + +(1) ``router``: RouterInfo declared in extension which overrides the one + pre-registered at ``RouterFactory`` + +(2) ``features``: features of RouterInfo. Currently it should be one of the + below. + + Features should be a list of strings describing router characteristics, and + the ordering does not matter since it is interpreted as a *set* internally. + (``['ha', 'distributed']`` and ``['distributed', 'ha']`` are the same) + + - ``[]``: No feature. (e.g. ``LegacyRouter``) + - ``['distributed']``: Distributed router. (e.g. ``DvrEdgeRouter``, + ``DvrLocalRouter``) + - ``['ha']``: HA router. (e.g. ``HaRouter``) + - ``['ha', 'distributed']``: Distributed HA router. (e.g. + ``DvrEdgeHaRouter``, ``DvrLocalRouter``) + + Note that a router with the feature of ``['ha', 'distributed']`` can be + ``DvrLocalRouter`` when L3 agent mode is not ``dvr_snat`` [4]_. + +L3 extensions can override the *RouterInfo* class implemented in the Neutron +codebase when it is initialized using the *initialize* function. + + +Implementation +============== + +Assignee(s) +----------- + +* Yang Youseok + +Work Items +---------- + +* Add *RouterInfo* registration in *L3AgentExensionAPI* and pre-register + existing *RouterInfo* to *L3NATAgent*. [5]_ +* Add new exception named *RouterNotFoundInRouterFactory* to *neutron_lib*. + [6]_ + + +References +========== + +.. [1] `networking-odl`: + https://github.com/openstack/networking-odl/blob/master/networking_odl/l3/l3_odl_v2.py#L47 + +.. [2] `networking-ovn`: + https://github.com/openstack/networking-ovn/blob/master/networking_ovn/l3/l3_ovn.py#L50 + +.. [3] `networking-calico`: + https://github.com/openstack/networking-calico/blob/master/networking_calico/plugins/calico/plugin.py#L26 + +.. [4] https://docs.openstack.org/neutron/latest/configuration/l3-agent.html#DEFAULT.agent_mode + +.. [5] https://review.openstack.org/#/c/620349/ + +.. [6] https://review.openstack.org/#/c/620348/