Relationships

Relationships define the nature of interaction between interconnected components in Meshery. They represent various types of connections and dependencies between components no matter the genealogy of the relationship such as parent, siblings, binding. Relationships have selectors, metadata, and optional parameters.

Contributing a new Relationship

contributing to relationships

Semantic and Non-Semantic Relationships

Shapes (all styles) convertable to Components

The isAnnotation attribute of a Component determines whether the give Component reflects an infrastructure concern - is sematically meaningful, and whose lifecycle is managed by Meshery.

Core Constructs of Relationships

  • Kinds
  • Subtypes
  • Selectors

Kind - Subtypes of Relationships

The combination of kind and subType uniquely determines the visual paradigm for a given relationship i.e., relationships with the same kind and subType will share an identical visual representation regardless of the specific components involved in the relationship.

1. Edge - Network

Configures the networking.

Example

  • Service –> Deployment,
  • Service –> Pod,
  • IngressController –> Ingress –> Service

2. Edge - Mount

Example

Assignment of PersistentVolumes to Pods via PersistenVolumeClaim .

  • Pod –> PersistenVolumeClaim –> PersistentVolume

3. Edge - Permission

Example

The set of Service Accounts that are entitled with the one or more Roles/ClusterRoles bound via Role/ClusterRoleBinding.

  • ClusterRole –> CluserRoleBinding –> ServiceAccount
  • Role –> RoleBinding –> ServiceAccount

4. Edge - Firewall

Example

Kubernetes Network Policy for controlling ingress and egress traffic from Pod-to-Pod

  • Pod –> NetworkPolicy –> Pod

5. Heirarchical - Inventory

Example

  • WASMFilter (binary and configuration) –> IstioWASMPlugin
  • WASMFilter (binary and configuration) –> IstioEnvoyFilter

6. Heirarchical - Parent

Example

Any namespaced Kubernetes component –> Kubernetes Namespace

Selectors in Relationships

Structure of Selectors

Selectors are structured as an array, wherein each entry comprises a ‘from(self)’ field and a ‘to(other)’ field ([from: [{..}], to: [{..}]]), delineating the components involved in a particular relationship. These entries define the constraints necessary for the existence of said relationship, thus providing scoping within a relationship. Each item in the selector, uniquely defines a relation between the components listed. i.e. from and to fields are evaluated within the context of the selector.

This arrangement enhances flexibility and reusability in the definition and configuration of relationships among components.

Example Selector

Selectors can be applied to various components, enabling a wide range of relationship definitions. Here are some examples:

  1. ConfigMap - Pod
  2. ConfigMap - Deployment
  3. WASMFilter - EnvoyFilter

The above pairs have hierarchical inventory relationships, and visual paradigm remain consistent across different components. A snippet of the selector backing this relationship is listed below.

Selector _https://github.com/meshery/meshery/blob/master/server/meshmodel/kubernetes/relationships/hierarchical_inventory.json_ ```json selector: [ { "allow": { "from": [ { "kind": "WASMFilter", "model": "istio-base", "patch": { "patchStrategy": "replace", "mutatorRef": [ [ "settings", "config" ], [ "settings", "wasm-filter" ] ], "description": "WASM filter configuration to be applied to Envoy Filter." } } ], "to": [ { "kind": "EnvoyFilter", "model": "istio-base", "patch": { "patchStrategy": "replace", "mutatedRef": [ [ "settings", "configPatches", "_", "patch", "value" ] ], "description": "Receive the WASM filter configuration." } } ] }, "deny": { ... } }, { "allow": { "from": [ { "kind": "ConfigMap", "model": "kubernetes", "patch": { "patchStrategy": "replace", "mutatorRef": [ [ "name" ] ], "description": "In Kubernetes, ConfigMaps are a versatile resource that can be referenced by various other resources to provide configuration data to applications or other Kubnernetes resources.\n\nBy referencing ConfigMaps in these various contexts, you can centralize and manage configuration data more efficiently, allowing for easier updates, versioning, and maintenance of configurations in a Kubernetes environment." } } ], "to": [ { "kind": "Deployment", "model": "kubernetes", "patch": { "patchStrategy": "replace", "mutatedRef": [ [ "spec", "containers", "_", "envFrom", "configMapRef", "name" ] ], "description": "Deployments can reference ConfigMaps to inject configuration data into the Pods they manage. This is useful for maintaining consistent configuration across replica sets.\n\nThe keys from the ConfigMap will be exposed as environment variables to the containers within the pods managed by the Deployment." } } ] }, "deny": { ... } } ] ``` The `selector` defined for the relationship between `WasmFilter` and `EnvoyFilter` (the first item in the array) is entirely distinct from the `selector` defined for the relationship between `ConfigMap` and `Deployment`. This ensures independence in how these components relate to each other while still permitting similar types of relationships.

Types of Relationships

  1. Inventory
  2. Mount
  3. Firewall
  4. Permission
  5. Network

Hierarchical Relationships

When defining relationships that involve a large number of combinations between from and to, selectors provide a mechanism to organize and manage these relationships hierarchically. This prevents the need for crafting complex deny attributes and facilitates easier maintenance.

Patch Strategies

Patches in Meshery relationships utilize strategies and references (mutatorRef/mutatedRef) for the from and to fields. These convey the property path that will be updated as the relationship is created.

Meshery Registry

You can reference and search the full set of registered relationships in Meshery UI –> Setttings –> Registry

Future Feature

mesheryctl model import -f [ oci:// | file:// ]`

Suggested Reading

  • Components - Meshery Components identify and characterize infrastructure under management.
  • Connections - Meshery Connections are managed and unmanaged resources that either through discovery or manual entry are managed by a state machine and used within one or more Environments.
  • Credentials - Meshery uses one or more Credentials when authenticating to a managed or unmanaged Connection.
  • Designs - Meshery Designs are descriptive, declarative characterizations of how your Kubernetes infrastructure should be configured.
  • Environments - Meshery offers support for Kubernetes cluster and cloud state synchronization with the help of MeshSync.
  • Models - Meshery uses a set of resource models to define concrete boundaries to ensure extensible and sustainable management.
  • Patterns - Meshery Patterns are descriptive, declarative characterizations of how your Kubernetes infrastructure should be configured.
  • Policies - Meshery Policies enable you with a broad set of controls and governance of the behavior of systems under Meshery's management.
  • Workspaces - Meshery Workspaces act as central collaboration point for teams.