An application that can be ordered. It is automatically provisioned, can be consumed by a service consumer and generally adheres to our quality requirements.
- Service Consumer
An application that connects to a service instance as a client.
- Service Order
The act of deploying a Kubernetes resource that triggers the provisioning of a new service instance.
- Service Instance
A single isolated occurrence of a service.
Services can be provisioned on various places:
- Converged Cluster
Service instance runs on the same cluster as the service consumer.
- Service Cluster
Service runs on one or more dedicated clusters, reserved for services.
- Cloud Service
A type of service architecture offered by a cloud service provider such as AWS or GCP.
- Converged Service
A type of service developed to run on a converged cluster.
- Converged Service Architectures
Architecture refers to the deployment strategy of a service instance in relation to high availability.
A Composition refers to the key Crossplane API type that configures how Crossplane should compose resources into a higher level "composite resource". A Composition tells Crossplane "when someone creates composite resource X, you should respond by creating resources Y and Z".
A "Composite Resource" or "XR" is an API type defined using Crossplane. A composite resource’s API type is arbitrary - dictated by the concept the author wishes to expose as an API. A common convention is for types to start with "X" - for example "XAcmeCoDB".
A composite resource can be thought of as the interface to a Composition. It provides the inputs a Composition uses to compose resources into a higher level concept. In fact, the composite resource is the high level concept.
A "Composite Resource Definition" or "XRD" is the API type used to define new types of composite resources and claims. Types of composite resources and types of claims exist because they were defined into existence by an XRD. The XRD configures Crossplane with support for the composite resources and claims that make up a platform API.
Each claim corresponds to a composite resource, and the pair have nearly identical schemas.
In the context of AppCat, a resource claim is created in the user’s namespace, which binds a cluster-scoped composite resource.