Contributing to Models

Meshery’s internal object model is designed to provide a consistent and extensible way of capturing and characterizing the resources under Meshery’s management and the capabilities Meshery has at its disposal. Meshery Models serve as the unit of packaging for the object models that define a registered capability or a type of managed infrastructure and their relationships, and details specifics of how to manage them.

Models often represent infrastructure and application technologies, however, they are also capable of defining other types of constructs like annotations, like shapes (infrastructure ambiguous components). Models are used to define the capabilities of Meshery.

See the Meshery Registry to learn more.

Model Construct Classification Figure: Model Construct Classification

Meshery Constructs and their Lifecycle

This section aids in your understanding of the vernacular of Meshery’s internal object model and discusses the difference beteween schemas, definitions, declarations, and instances

The lifecycle of Meshery entities (components, relationships, policies) is represented by the following terms, which are used to describe the various stages of a Model’s lifecycle:

Schema

Schema (static) : the skeletal structure representing a logical view of the size, shape, characteristics of a construct.

The schema represents the skeletal structure of a construct and provides a logical view of its size, shape, and characteristics. It defines the expected properties and attributes of the construct. The schema serves as a blueprint or template for creating instances of the construct. It is a static representation that defines the structure and properties but does not contain specific configuration values.

Schema example

Component schema excerpt
 {
"$id": "https://schemas.meshery.io/component.json",
  "$schema": "http://json-schema.org/draft-07/schema#",
"description": "Components are the atomic units for designing infrastructure. Learn more at https://docs.meshery.io/concepts/components",
"required": [
"apiVersion",
"kind",
"schema",
"model"
],
"additionalProperties": false,
"type": "object",
"properties": {
"apiVersion": {
"type": "string",
"description": "API Version of the component."
},
"kind": {
"type": "string",
"description": "Kind of the component."
.
.
.
See github.com/meshery/schemas for more details.

Definition

Definition (static) : An implementation of the Schema containing an outline of the specific attributes of a given, unconfigured construct.

A definition is an implementation of the schema. It contains specific configurations and values for the construct at hand. The definition provides the actual configuration details for a specific instance of the construct. It is static because it is created based on the schema but does not change once created. The definition is used to instantiate instances of the construct.

Definition example

a generic, unconfigured Kubernetes Pod.

Declaration

Declaration (static) : - A configured construct with detailed intentions of a given Definition.

Declaration example

NGINX container as a Kubernetes Pod with port 443 and SSL termination.

Instance

Instance (dynamic) : A realized construct (deployed/discovered); An instantiation of the declaration.

An instance represents a realized construct. An instance is a dynamic representation that corresponds to a deployed or discovered instantiation of a declaration. An instance is created based on its corresponding definition and represents an actual running or deployed version of the construct within the environment.

Instance example

NGINX-as234z2 pod running in a cluster as a Kubernetes Pod with port 443 and SSL termination.

Generating Models does not require Meshery Server

Model and Component generation logic is MeshKit. mesheryctl and Meshery Server both utilize MeshKit’s libraries for ongoing programmatic generation of models and components. For adding a model, the link to the CRDs for the specific model needs to be added to the Meshery Integration Spreadsheet. On adding the link to the Meshery Integration Spreadsheet, the model generator automatically registers the specific model with Meshery.

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