Instance Model Considerations dpalmavnomic com Instance Model Objectives
Instance Model Considerations dpalma@vnomic. com
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. 2. Deriving the instance model from Templates, Types 1. Accessing the instance model 1. Orchestration time is already covered for the basic case 2. Post orchestration, i. e. how do you look at the current state? 3. 4. 5. Is there complete information? 1. 2. 3. Information is can be passed to operations (declarative) but workflows require more Workflows may only see a part of the model, i. e. the nodes in defined states No navigation possible or definition of from where and in what runtime 1. 2. From outside the topology via some (REST? ) endpoint? Access properties, attributes, invoke operations? (like a workflow would do post initial deployment) Are inputs, outputs, active policies, etc. also available? Instance model updates 1. 2. What is visible during orchestration? E. g. lifecycle events, error status. How are topology and node status changes reflected over time? Change events? Snapshots? … Serialization 1. It’s convenient to obtain a serialized representation of the entire model 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 Type Schema Templates Types Instances Type w … Type x derived from Properties name: type attributes Met model of a TOSCA Type E. g. Class, data type, references, attributes Node. Type, Capability. Type, … Template y Type x properties attributes Instance z Template y properties Attributes Dynamic info Normative? Env specific Parameterized “constructors”
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