TOSCA Interface

A TOSCA interface is available for configuring and controlling CORD. It is auto-generated from the set of models configured into the POD manifest, and includes both core and service-specific models.

In CORD-4.0 this TOSCA interface is released as an alpha feature.

What is TOSCA?

Topology and Orchestration Specification for Cloud Applications (TOSCA) is an OASIS standard language to describe a topology of cloud based web services, their components, relationships, and the processes that manage them. The TOSCA standard includes specifications to describe processes that create or modify web services. You can read more about it on the OASIS website.

CORD extends the TOSCA specification to support custom models for services, allow operators to manage them with a simple and well-known YAML interface.

Internals

The xos-tosca container autogenerates the TOSCA interface starting from the xproto definition. When the xos-tosca container starts, it connects to xos-core via the gRPC API to fetch all the xproto definition of the onboarded models. This includes both core and service models. Then using the xos-genx toolchain, it will generates the corresponding TOSCA specifications.

For example, the xproto definition of a compute node in XOS is:

message Node::node_policy (XOSBase) {
     required string name = 1 [max_length = 200, content_type = "stripped", blank = False, help_text = "Name of the Node", null = False, db_index = False];
     required manytoone site_deployment->SiteDeployment:nodes = 2 [db_index = True, null = False, blank = False];
}

which is then transformed in the following TOSCA spec:

tosca_definitions_version: tosca_simple_yaml_1_0

node_types:

    tosca.nodes.Node:
        derived_from: tosca.nodes.Root
        description: "An XOS Node"
        capabilities:
            node:
                type: tosca.capabilities.xos.Node
        properties:
            must-exist:
                type: boolean
                default: false
                description: Allow to reference existing models in TOSCA recipes
            name:
                type: string
                required: false
                description: "Name of the Node"
            

    tosca.relationships.BelongsToOne:
        derived_from: tosca.relationships.Root
        valid_target_types: [ tosca.capabilities.xos.SiteDeployment ]
    

    tosca.capabilities.xos.Node:
        derived_from: tosca.capabilities.Root
        description: Node

In TOSCA terminology, the above woule be called a TOSCA node type (although confusingly, it's defined for the Node model in CORD, which represents a server).

Using TOSCA

Once CORD is up and running, a node can be added to a POD using the TOSCA interface by uploading the following recipe:

tosca_definitions_version: tosca_simple_yaml_1_0

description: Load a compute node in XOS

imports:
   - custom_types/node.yaml

topology_template:
  node_templates:

    # A compute node
    GratefulVest:
      type: tosca.nodes.Node
      properties:
        name: Grateful Vest

In TOSCA terminology, the above would be called a TOSCA node template.