Inserting a Redfish Aggregator

[James Feist]

On 12/3/19 7:14 PM, Richard Hanley wrote:
> Hi everyone,
> 
> 
> I’ve been thinking a bit about how to separate Redfish logic from DBus 
> in bmcweb.
> 
> 
> As a motivating example, imagine a Redfish aggregator that has some 
> chassis that is located outside of its local instance.Once the 
> aggregator finds the external chassis, it needs to add it to the chassis 
> collection.
> 
> 
> However, looking at the current implementation of the 
> ChassisCollection.(located here: 
> https://github.com/openbmc/bmcweb/blob/master/redfish-core/lib/chassis.hpp#L246) 
> It isn’t clear to me how to add this in.
> 
> 
> The current implementation does some setup on the response payload, and 
> then makes a DBus call to look through the entity manager.The collection 

It's not entity-manager per-say, it's whatever daemon produces the 
correct interface on d-bus. Entity-manager is just one option.

> it sends as a response is entirely defined by the result from the entity 
> manager. I basically see three ways that this could be solved.
> 
> 
>  1. Move the aggregator logic down to the entity manager
>  2. Refactor the Chassis Collection to have its own data model separate
>     from the entity manager.
>  3. Create some service that works on top of the bmcweb implementation
>     of Redfish.
> 
> 
> I think this comes up to a fundamental design decision, how 
> modular/flexible should the Redfish implementation be?Right now bmcweb 
> provides a very sane default implementation, and is tied very closely to 
> the current hardware it is running on.Whereas I am envisioning a Redfish 
> implementation that is a bit more abstracted from any particular hardware.
> 

Can you describe a bit more where the data would come from? Are you 
thinking of multiple bmcs that are physically attached? Non-physically 
attached bmcs? BMCs not running OpenBmc? One idea I had in the past was 
remoting dbus from other systems in some way and creating a clone daemon 
that would show the interfaces from the other systems, although I never 
looked into it much.

> 
> It’s taken me awhile to get up to speed with Redfish, Open BMC, and 
> Google’s infrastructure; but I’m starting to get a more concrete design 
> for an aggregator.However, I’m unsure about whether this should be 
> framed as a new layer on top of the existing implementation, or as a 
> refactor of that implementation?
> 
> 
> I can see some pros and cons between the two, but I’m interested in how 
> everyone feels about this.
> 
> 
> Regards,
> 
> Richard
>