[openstack-dev] [Neutron] Alternative approaches for L3 HA

Morales, Victor victor.morales at intel.com
Tue Feb 14 15:24:55 UTC 2017


Hey Lubosz,

First of all, good job responding to the concerns of users and keeping a healthy OpenStack ecosystem.  I’ve one comment about this email,  maybe it was a cultural thing but I found it a little aggressive, specially the use of some pronouns and names.  I know you and I’m completely sure that your intention was to help others in the best way, hopefully this is not a blind spot.

Regards,
Victor Morales

From: "Kosnik, Lubosz" <lubosz.kosnik at intel.com<mailto:lubosz.kosnik at intel.com>>
Reply-To: "OpenStack Development Mailing List (not for usage questions)" <openstack-dev at lists.openstack.org<mailto:openstack-dev at lists.openstack.org>>
Date: Monday, February 13, 2017 at 10:23 PM
To: "OpenStack Development Mailing List (not for usage questions)" <openstack-dev at lists.openstack.org<mailto:openstack-dev at lists.openstack.org>>
Subject: Re: [openstack-dev] [Neutron] Alternative approaches for L3 HA

So from my perspective I can tell that problem is completely in architecture and even without something outside of Neutron we cannot solve that.
Two releases ago I started to work on hardening that feature but all my ideas was killed by Armando and Assaf. The decided that adding outside dependency will open the doors for a new bugs from dependencies into Neutron [1].

You need to know that there are two outstanding bugs in this feature. There is a internal and outside connectivity split brain. [2] this patch made by me is “fixing” part of the problem. It allows you specify additional tests to verify connectivity from router to GW.
Also there is a problem with connectivity between network nodes. It’s more problematic and like you said it’s unsolvable in my opinion without using external mechanism.

If there will be any need to help with anything I would love to help with sharing my knowledge about this feature and what exactly is not working. If anyone needs any help with anything about this please ping me on email or IRC.

[1] https://bugs.launchpad.net/neutron/+bug/1375625/comments/31
[2] https://review.openstack.org/#/c/273546/

Lubosz

On Feb 13, 2017, at 4:10 AM, Anna Taraday <akamyshnikova at mirantis.com<mailto:akamyshnikova at mirantis.com>> wrote:

To avoid dependency of data plane on control plane it is possible to deploy a separate key-value storage cluster on data plane side, using the same network nodes.
I'm proposing to make some changes to enable experimentation in this field, we are yet to come up with any other concrete solution.

On Mon, Feb 13, 2017 at 2:01 PM <cristi.calin at orange.com<mailto:cristi.calin at orange.com>> wrote:

Hi,





We also operate using Juno with the VRRP HA implementation and at had to patch through several bugs before getting to the Mitaka release.

An pluggable, drop-in alternative would be highly appreciated. However our experience has been that the decoupling of VRRP from the control plane is actually a benefit as when the control plane is down the traffic is not affected.

In a solution where the L3 HA implementation becomes tied to the availability of the control plane (etcd cluster or any other KV store) then an operator would have to account for extra failure scenarios for the KV store which would affect multiple routers than the outage of a single L3 node which is the case we usually have to account now.





Just my $.02



Cristian



From: Anna Taraday [mailto:akamyshnikova at mirantis.com<mailto:akamyshnikova at mirantis.com>]
Sent: Monday, February 13, 2017 11:45 AM
To: OpenStack Development Mailing List (not for usage questions)
Subject: Re: [openstack-dev] [Neutron] Alternative approaches for L3 HA



In etcd for each HA router we can store key which will identify which agent is active. L3 agents will "watch" this key.
All these tools have leader election mechanism which can be used to get agent which is active for current HA router.



On Mon, Feb 13, 2017 at 7:02 AM zhi <changzhi1990 at gmail.com<mailto:changzhi1990 at gmail.com>> wrote:

Hi, we are using L3 HA in our production environment now. Router instances communicate to each other by VRRP protocol. In my opinion, although VRRP is a control plane thing, but the real VRRP traffic is using data plane nic so that router namespaces can not talk to each other sometimes when the  data plan is busy. If we were used etcd (or other), does every router instance register one "id" in etcd ?





Thanks

Zhi Chang

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Regards,
Ann Taraday

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