Instance Model Considerations

Instance Model Objectives Provide complete representation of the state of a TOSCA service template deployment So it can be understood and appreciated by the owner So a workflow can change it So state or topology changes can be understood over time So lifecycle operations can be manually applied to parts of it Harmonize manual and autonomic operations … We need to define objectives AND non-objectives Let’s come back to this after we survey the technique issues

General Issues 1.Deriving the instance model from Templates, Types 1.Is there complete information? 2.Accessing the instance model 1.Orchestration time is already covered for the basic case 1.Information is can be passed to operations (declarative) but workflows require more 2.Workflows may only see a part of the model, i.e. the nodes in defined states 3.No navigation possible or definition of from where and in what runtime 2.Post orchestration, i.e. how do you look at the current state? 1.From outside the topology via some (REST?) endpoint? 2.Access properties, attributes, invoke operations? (like a workflow would do post initial deployment) 3.Are inputs, outputs, active policies, etc. also available? 3.Instance model updates 1.What is visible during orchestration? E.g. lifecycle events, error status. 2.How are topology and node status changes reflected over time? Change events? Snapshots? … 4.Serialization 1.It’s convenient to obtain a serialized representation of the entire model 5.Correlation of modeled entities with external entities

Deriving the instance model Service template instantiation Templates represent the entities that can be created But cardinality may vary Orchestrator will compute/know the cardinality at some point Processing the templates Apply inputs All aspects of the service template must be resolved (substitutable, sub-topologies, …) Policies matched and intantiated Additional entities provided by environment might also appear Load balancer, Backup, Directory service, Monitoring, DNS, NTP endpoints … Location/placement of container entities and resources

Information Model Instance z Template y properties Attributes Dynamic info Normative? Env specific TemplatesInstancesType Schema Types Met model of a TOSCA Type E.g. Class, data type, references, attributes Template y Type x properties attributes Type x derived from Properties name: type attributes Type w … NodeType, CapabilityType, … Parameterized “constructors”