Specification for the BP l3-high-availability
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Sylvain Afchain
Mark McClain
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specs/juno/l3-high-availability.rst
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specs/juno/l3-high-availability.rst
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..
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This work is licensed under a Creative Commons Attribution 3.0 Unported
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License.
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http://creativecommons.org/licenses/by/3.0/legalcode
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=================================
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Neutron/L3 High Availability VRRP
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=================================
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Launchpad blueprint:
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https://blueprints.launchpad.net/neutron/+spec/l3-high-availability
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The aim of this blueprint is to add High Availability Features on
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virtual routers.
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High availability features will be implemented as extensions and drivers.
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A first driver on the agent side will be based on Keepalived.
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A new scheduler will be also added in order to be able to spawn multiple
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instances of a same router on many agents for the redundancy.
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The DVR blueprint will leverage this proposal as a Service node specifically
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for SNAT traffic. See the reference for the DVR BP at the end of this
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specification
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Problem description
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===================
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Currently we are able to spawn more than one l3 agent, and a l3 agent is able
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to handle more than one external network, however each l3 agent is a SPOF.
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If an l3 agent fails, all virtual routers of this agent will be lost,
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and consequently all VMs connected to these virtual routers will be isolated.
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Proposed change
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===============
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For the Neutron server side:
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The idea of this blueprint is to schedule a virtual router to at least two l3
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agents, but this limit could be increased by changing a parameter in the
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neutron configuration file.
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For the Neutron L3 agent side:
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The current router interfaces management in the l3 agent will be abstracted in
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order to introduce the possibility to add drivers for that purpose. As a first
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implementation of a driver, an HA Keepalived driver will be added. All the IPs
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will be converted to VIPs.
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In order to hide the HA traffic from the tenant point of view a HA network will
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be added and all the virtual router instances will be connected through a HA
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port to this network.
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Flows::
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+----+ +----+
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| | | |
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+-------+ QG +------+ +-------+ QG +------+
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| | | | | | | |
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| +-+--+ | | +-+--+ |
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| VIPs| | | |VIPs |
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| | +--+-+ +--+-+ | |
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| + | | | | + |
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| KEEPALIVED+---+ HA +------+ HA +----+KEEPALIVED |
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| + | | | | + |
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| | +--+-+ +--+-+ | |
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| VIPs| | | |VIPs |
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| +-+--+ | | +-+--+ |
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| | | | | | | |
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+-------+ QR +------+ +-------+ QR +------+
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+----+ +----+
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As a phase 2 of the keepalived driver implementation, the Keepalived driver
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will start a conntrackd instance in order to not lose the established
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connections when switching from the active to standby.
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Alternatives
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------------
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The first driver is going to be based on Keepalived. We could use some
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alternative drivers based on other protocols for ex: Common Address Redundancy
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Protocol (CARP).
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By default a config parameter will be added in order to specify whether the
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virtual routers will be HA or not. In addition, an admin-only API is introduced
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which will allow admins to migrate existing routers to HA mode.
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Data model impact
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-----------------
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Two new columns will be added to the router_extra_attributes table in order to
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specify whether the virtual router will be HA or not and to specify the virtual
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router id.
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+------------+-------+---------+---------+------------+---------------------+
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|Attribute |Type |Access |Default |Validation/ |Description |
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|Name | | |Value |Conversion | |
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+============+=======+=========+=========+============+=====================+
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|ha |bool |RW, admin|False |N/A |Set router as HA |
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|ha_vr_id |int |RW, admin|N/A |N/A |HA virtual router id |
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+------------+-------+---------+---------+------------+---------------------+
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The ha_vr_id will be limited to 255 due to VRRP protocol. This limit will have
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to be removed when introducing a new driver without this limitation.
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A new table will be introduced to specify the association between a router,
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the agents and the HA ports that are going to be used for the HA
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administrative traffic.
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+------------+-------+---------+---------+------------+----+---------------+
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|Attribute |Type |Access |Default |Validation/ |Key |Description |
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|Name | | |Value |Conversion | | |
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+============+=======+=========+=========+============+====+===============+
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|port_id |UUID |RW, admin|N/A |N/A |PRI |HA port id |
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+------------+-------+---------+---------+------------+----+---------------+
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|router_id |UUID |RW, admin|N/A |N/A | | |
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+------------+-------+---------+---------+------------+----+---------------+
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|l3_agent_id |UUID |RW, admin|N/A |N/A | | |
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+------------+-------+---------+---------+------------+----+---------------+
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|priority |int |RW, admin|50 |N/A | | |
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+------------+-------+---------+---------+------------+----+---------------+
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|state |enum |RW, admin|N/A |N/A | |active/standby |
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+------------+-------+---------+---------+------------+----+---------------+
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REST API impact
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---------------
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router-create Create a router for a given tenant.
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::
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router-create --name another_router --ha=true
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Admin can only set this attribute. The tenants need not be aware about
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this attribute in the router table. So it is not visible to the tenant.
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Request
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::
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POST /v2.0/routers
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Accept: application/json
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{
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"router":{
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"name":"another_router",
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"admin_state_up":true,
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"ha":true}
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}
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Response
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::
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{
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"router":{
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"status":"ACTIVE",
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"external_gateway_info":null,
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"name":"another_router",
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"admin_state_up":true,
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"ha":true,
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"tenant_id":"6b96ff0cb17a4b859e1e575d221683d3",
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"id":"8604a0de-7f6b-409a-a47c-a1cc7bc77b2e"}
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}
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router-show Show information of a given router.
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Request
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::
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GET /v2.0/routers/a9254bdb-2613-4a13-ac4c-adc581fba50d
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Accept: application/json
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Response
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::
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{
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"routers":[{
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"status":"ACTIVE",
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"external_gateway_info":{
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"network_id":""
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},
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"name":"router1",
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"admin_state_up":true,
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"ha":true,
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"tenant_id":"33a40233088643acb66ff6eb0ebea679",
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"id":"a9254bdb-2613-4a13-ac4c-adc581fba50d"}]
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}
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router-update Create a router for a given tenant.
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Admin can only update the HA mode of a router.
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Admin only context:
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::
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neutron router-update router1 --ha=True
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Security impact
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---------------
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None
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Notifications impact
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--------------------
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None
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Other end user impact
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---------------------
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None
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Performance Impact
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------------------
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There will be no network performance impact. Spawning a new virtual router may
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be a bit longer due to the delay of starting the Keepalived/Conntrackd
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processes.
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Other deployer impact
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---------------------
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Since this implementation relies on Keepalived, Keepalived will have to be
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deployed on each l3 node. The required version of Keepalived is the
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version 1.2.0 in order to have the IPV6 support.
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In addition, conntrackd will be required to be run on each node.
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There is no plan to migrate automatically the original virtual routers to
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the HA virtual routers when updating a previous Openstack installation.
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So after a migration and with the l3_ha configuration parameter set to "True",
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the new routers created will be HA while the older ones will be unchanged.
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Cloud admins can migrate existing virtual routers to be HA routers by using
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the new API. This API is not exposed to tenants.
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Developer impact
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----------------
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None
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Implementation
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==============
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Assignee(s)
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-----------
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Primary assignee:
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Sylvain Afchain <sylvain-afchain>
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Other contributors:
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Assaf Muller <amuller>
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Work Items
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----------
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1. HA L3 Extension, DB bases
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2. HA L3 Scheduler
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3. Keepalived manager
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4. L3 agent driver abstraction introduction, Keepalived driver
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5. Conntrackd support
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Dependencies
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============
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None
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Testing
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=======
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The code will be covered by unit tests.
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When multi-nodes test will be available, tempest test will be introduced.
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A document explaining how to test all the patches during the review
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process will be updated here :
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https://docs.google.com/document/d/1P2OnlKAGMeSZTbGENNAKOse6B2TRXJ8keUMVvtUCUSM
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Documentation Impact
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====================
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Document deployer impacts.
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References
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==========
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https://review.openstack.org/#/q/topic:bp/l3-high-availability,n,z
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https://git.openstack.org/cgit/openstack/neutron-specs/tree/specs/juno/neutron-ovs-dvr.rst
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https://wiki.openstack.org/wiki/Neutron/L3_High_Availability_VRRP
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