RE: [tosca] RE: updated operational model

From: Bruun, Peter Michael (CMS RnD Orchestration) <peter-michael.bruun@hpe.com>
Sent: Thursday, February 10, 2022 9:15 AM
To: Calin Curescu <calin.curescu@ericsson.com>; Chris Lauwers <lauwers@ubicity.com>; tosca@lists.oasis-open.org
Subject: RE: [tosca] RE: updated operational model

Hi Calin,

I concur totally with what you propose. I am sure that several of us have actually implemented something like this, and for me it works nicely.

Yes, my implementation works exactly like that.

I am, however, noting that some members object strongly to the idea of a âdependency graphâ driving orchestration. Deriving a dependency graph from Relationships is, as far as I am aware, not part of the our TOSCA standardization. So this would be completely up to the profiles to define.

Iâm not sure I understand this statement. Isnât a TOSCA topology graph (which consists of nodes and relationships) an explicit encoding of the dependencies between the various components that make up a service? If youâre using âpure TOSCAâ orchestration, then this graph absolutely drives orchestration. On the other hand, you could also ignore TOSCAâs orchestration features (such as interfaces, operations, notifications, workflows, etc.) and just hand off the âtopology representation graphâ created using TOSCA to a 3^rd-party orchestrator. Tal has now shown us three different examples of this approach (with Kubernetes, Ansible, and Terraform).

The ETSI standard does define how a template can refer to a previous/subsequent version of itself, although the way it is done there is perhaps not the best design.

This statement would suggest that your earlier âdependencyâ comment refers to dependencies between different versions of the same template. Am I misunderstanding?

Peter

Thanks,

Chris

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