[Openstack-operators] [nova] Do you, or your users, have input on how get-me-a-network should work in Nova?
Kris G. Lindgren
klindgren at godaddy.com
Fri Feb 19 22:48:29 UTC 2016
Senior Linux Systems Engineer
On 2/19/16, 10:07 AM, "Matt Riedemann" <mriedem at linux.vnet.ibm.com> wrote:
>There is a long contentious dev thread going on here  about how Nova
>should handle the Neutron auto-allocate-topology API (referred to as the
>The point is to reduce the complexity for users to simply boot an
>instance and be able to ssh into it without having to first setup
>networks/subnets/routers in neutron and then specify a nic when booting
>the instance. If the planets are aligned, and no nic is provided (or
>available to the project), then nova would call the new neutron API to
>auto-allocate the network and use that to create a port to associate
>with the instance.
>There is existing behavior in Nova where you can boot an instance and
>get no networking with neutron as the backend. You can later add
>networking by attaching an interface. The nova dev team has no idea how
>common this use case is though.
>There will be a microversion to the nova API with the get-me-a-network
>support. The debate is what the default behavior should be when using
>that microversion. The options are basically:
>1. If no nic is provided at boot and none are available, don't provide a
>network (existing behavior). If the user wants a network auto-allocated,
>they specify something like: --nic=auto
This is my preferred choice - keep the functionality exactly the same as the way it is today. Users (if this is available) can opt-in. Not 100% familiar with micro-version - but is it possible to opt-out of this micro-version all together, but have other, later, micro-versions?
>In this case the user has to opt into auto-allocating the network.
>2. If no nic is provided at boot and none are available, nova will
>attempt to auto-allocate the network from neutron. If the user
>specifically doesn't want networking on instance create (for whatever
>reason), they have to opt into that behavior with something like: --nic=none
>This is closer in behavior to how booting an instance works with
>nova-network, but it is a change in the default behavior for the neutron
>case, and that is a cause for concern for any users that have written
>tools to expect that default behavior.
I don't like this but I think other people might. Really I would like to see a config option detailing how the cloud admin wants to handle this behavior.
>3. If no nic is provided at boot and none are available, fail the
>request and force the request to be explicit, i.e. provide a specific
>nic, or auto, or none. This is a fail-fast scenario to force users to
>really state what they want.
I don't like this option at all. You are chaning what people must provide on the bootline and this as far as I can tell is a breaking change.
>As with any microversion change, we hope that users are reading the docs
>and aware of the changes in each microversion, but we can't guarantee
>that, so changing default behavior (case 2) requires discussion and
>input, especially from outside the dev team.
>If you or your users have any input on this, please respond in this
>thread of the one in the -dev list.
>OpenStack-operators mailing list
>OpenStack-operators at lists.openstack.org
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