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On Mon, Sep 4, 2017 at 9:11 PM, Jay Pipes <jaypipes at gmail.com> wrote:
> On 09/01/2017 04:42 AM, Rua, Philippe (Nokia - FI/Espoo) wrote:
> > Will it be possible to include network bandwidth as a resource in 
> Nova scheduling, for VM placement decision?
> 
> Yes.
> 
> See here for a related Neutron spec that mentions Placement:
> https://review.openstack.org/#/c/396297/7/specs/pike/strict-minimum-bandwidth-support.rst
> 
> > Context: in telecommunication applications, the network traffic is 
> an important dimension of resource usage. For example, it is often 
> important to distribute "bandwidth-greedy" VMs to different compute 
> nodes. There were some earlier discussions on this topic, but I could 
> not find a concrete outcome. [1][2][3]
> >
> > After some reading, I wonder whether the Custom resource classes 
> can provide a generic mechanism? [4][5][6]
> 
> No :) Custom resource classes are antithetical to generic/standard
> mechanisms.
> 
> We want to add two *standard* resource classes, one called
> NET_INGRESS_BYTES_SEC and another called NET_EGRESS_BYTES_SEC which
> would represent the total bandwidth in bytes per second the for
> corresponding traffic directions.

While I agree that the end goal is to have standard resource classes 
for bandwidth I think custom resource classes are generic enough to 
model bandwidth resource. If you want to play with the bandwidth based 
scheduling idea based on Pike then custom resource classes are 
available as a tool for a proof of concept.

> 
> 
> What would be the resource provider, though? There are at least two
> potential answers here:
> 
> 1) A network interface controller on the compute host
> 
> In this case, the NIC on the host would be a child provider of the
> compute host resource provider. It would have an inventory record of
> resource class NET_INGRESS_BYTES_SEC with a total value representing 
> the
> entire bandwidth of the host NIC. Instances would consume some amount 
> of
> NET_INGRESS_BYTES_SEC corresponding to *either* the Nova flavor (if 
> the
> resources:NET_INGRESS_BYTES_SEC extra-spec is set) *or* to the sum of
> consumed bandwidth amounts from the port profile of any ports 
> specified
> when launching the instance (and thus would be part of the pci device
> request collection attached to the build request).
> 
> 2) A "network slice" of a network interface controller on the compute 
> host
> 
> In this case, assume that the NIC on the compute host has had its 
> total
> bandwidth constrained via traffic control so that 50% of its available
> ingress bandwidth is allocated to network A and 50% is allocated to
> network B.
> 
> There would be multiple resources providers, each with an inventory
> record of resource class NET_INGRESS_BYTES_SEC with a total value of 
> 1/2
> the total NIC bandwidth. Both of these resource providers would be 
> child
> providers of the compute host resource provider. One of these child
> resource providers will be decorated with the trait "CUSTOM_NETWORK_A"
> and the other with trait "CUSTOM_NETWORK_B".
> 
> The scheduler would be able to determine which resource provider to
> consume the NET_INGRESS_BYTES_SEC resources from by looking for a
> resource provider that has both the required amount of
> NET_INGRESS_BYTES_SEC as well as the trait required by the port 
> profile.
> If, say, the port profile specifies that the port is to go on a NIC 
> with
> access to network "A", then the build request would contain a request 
> to
> the scheduler for CUSTOM_NETWORK_A trait...

The above setup can be simulated with custom resource classes and 
individual resource providers per compute node connected to the given 
compute node's resource provider via an aggregate. You most probably 
need to simulate the above network traits with individual custom 
resource classes in Pike.

I definitely don't think it is something I would do in production based 
on Pike due to two reasons:
1) we have bugs in Pike GA that prevents nova to handle some edge cases 
(especially in VM moving scenarios)
2) I agree with Jay that nested providers and neutron support will 
allows us to do something much more cleaner in the future.

However I think Pike is a good base to build a PoC and gather feedback. 
For example I already foresee a need to model OVS packet processing 
limits and in the long run even include the capacity of the TOR 
switches into the picture.

> 
> 
> If you're coming to Denver, I encourage you to get with me, Sean 
> Mooney,
> Moshe Levi and others who are interested in seeing this work move 
> forward.

@Jay: sign me up for this list.

Cheers,
gibi

> 
> Best,
> -jay
> 
> > Here is what I have in mind:
> > - The VM need is specified in the flavor extra-specs, e.g. 
> resources:CUSTOM_BANDWIDTH=123.
> > - The compute node total capacity is specified in host aggregate 
> metadata, e.g. CUSTOM_BANDWIDTH=999.
> > - Nova then takes care of the rest: scheduling where the free 
> capacity is sufficient, and performing simple resource usage 
> accounting (updating the compute node free network bandwidth capacity 
> as required).
> >
> > Is the outline above according to current plans?
> > If not, what would be possible/needed in order to achieve the same 
> result, i.e. consider the VM network traffic need during VM placement?
> >
> > BR,
> > Philippe
> >
> > [1] 
> https://blueprints.launchpad.net/nova/+spec/bandwidth-as-scheduler-metric
> > [2] https://wiki.openstack.org/wiki/NetworkBandwidthEntitlement
> > [3] 
> https://openstack.nimeyo.com/80515/openstack-scheduling-bandwidth-resources-nic_bw_kb-resource
> > [4] https://docs.openstack.org/nova/latest/user/placement.html
> > [5] 
> http://specs.openstack.org/openstack/nova-specs/priorities/pike-priorities.html#placement
> > [6] https://review.openstack.org/#/c/473627/
> >
> > 
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