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Hi Lianhao Lu,

I briefly summarized my recollection of that session in this blueprint:

https://blueprints.launchpad.net/ironic/+spec/add-ceilometer-agent

I've responded to your questions inline as well.


On Sun, Nov 17, 2013 at 10:24 PM, Lu, Lianhao <lianhao.lu at intel.com> wrote:

> Hi stackers,
>
> During the summit session Expose hardware sensor (IPMI) data
> https://etherpad.openstack.org/p/icehouse-summit-ceilometer-hardware-sensors,
> it was proposed to deploy a ceilometer agent next to the ironic conductor
> to the get the ipmi data. Here I'd like to ask some questions to figure out
> what's the current missing pieces in ironic and ceilometer for that
> proposal.
>
> 1. Just double check, ironic won't provide API to get IPMI data, right?
>

Correct. This was generally felt to be unnecessary.

>
> 2. If deploying a ceilometer agent next to the ironic conductor, how does
> the agent talk to the conductor? Through rpc?
>

My understanding is that ironic-conductor will emit messages to the
ceilimeter agent, and the communication is one-way. These could be
triggered by a periodic task, or by some other event within Ironic, such as
a change in the power state of a node.


>
> 3. Does the current ironic conductor have rpc_method to support getting
> generic ipmi data, i.e. let the rpc_method caller specifying arbitrary
> netfn/command to get any type of ipmi data?
>

No, and as far as I understand, it doesn't need one.


>
> 4. I believe the ironic conductor uses some kind of node_id to associate
> the bmc with its credentials, right? If so, how can the ceilometer agent
> get those node_ids to ask the ironic conductor to poll the ipmi data? And
> how can the ceilometer agent extract meaningful information from that
> node_id to set those fields in the ceilometer Sample(e.g. recource_id,
> project_id, user_id, etc.) to identify which physical node the ipmi data is
> coming from?
>

This question perhaps requires a longer answer.

Ironic references physical machines (nodes) internally with an integer
node_id and externally with a standard uuid. When a Nova instance is
created, it will be associated to a node, that node will have a reference
to the nova instance_uuid which is exposed in our API, and can be passed to
Ceilometer's agent. I believe that nova instance_uuid will enable
ceilometer to detect the project, user, etc.

Should Ironic emit messages regarding nodes which are not provisioned?
Physical machines that don't have a tenant instance on them are not
associated to any project, user, tenant, quota, etc, so I suspect that we
shouldn't notify about them. It would be like tracking the unused disks in
a SAN.

Regards,
Devananda
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