Architecture Overview

DCM (Data Center Management) is a control plane for managing infrastructure services across multiple providers. This page gives a high-level overview of how the components fit together.

Components

    graph TD
    User["User (CLI / API)"]

    subgraph CP["Control Plane (:8080)"]
        CM["Catalog Manager"]
        PM["Policy Manager"]
        PLM["Placement Manager"]
        SPM["Service Provider Manager"]
    end

    subgraph Infrastructure
        PG["PostgreSQL"]
        NATS["NATS"]
    end

    subgraph Providers
        SP1["KubeVirt SP 1"]
        SP2["KubeVirt SP 2"]
    end

    User --> CP

    CM --> PG
    PM --> PG
    PLM --> PG
    SPM --> PG

    PLM --> PM
    PLM --> SPM
    CM --> PLM

    SPM --> NATS
    SP1 --> NATS
    SP2 --> NATS
    SP1 -->|self-register| SPM
    SP2 -->|self-register| SPM

Component Responsibilities

Component	Role
Control Plane	Single process that exposes all DCM APIs on `:8080`. Hosts the catalog, policy, placement, and service provider managers in one binary.
Catalog Manager	Manages service types, catalog items, and catalog item instances. Triggers placement when an instance is created.
Policy Manager	Stores placement policies (Rego) and evaluates them via an embedded OPA engine.
Placement Manager	Selects a service provider for a new instance by evaluating policies against available providers.
Service Provider Manager	Tracks registered service providers and their health status.
PostgreSQL	Persistent storage for the control plane.
NATS	Message bus for communication between the Service Provider Manager and service providers.
Service Providers	External systems (e.g., KubeVirt) that create and manage the actual resources (VMs, containers, etc.).

Request Flow

When a user creates a catalog item instance, the following happens:

    sequenceDiagram
    participant User
    participant CP as Control Plane
    participant CM as Catalog Manager
    participant PLM as Placement Manager
    participant PM as Policy Manager
    participant SPM as SP Manager
    participant SP as KubeVirt SP

    User->>CP: Create catalog item instance
    CP->>CM: POST /catalog-item-instances
    CM->>PLM: Request placement
    PLM->>PM: Evaluate policies (embedded OPA)
    PM-->>PLM: Placement decision
    PLM->>SPM: Create resource on provider
    SPM->>SP: Create VM
    SP-->>User: VM scheduling

The Catalog Manager receives the request and asks the Placement Manager to find a suitable provider.
The Placement Manager evaluates placement policies through the Policy Manager, which uses an embedded OPA engine to evaluate Rego.
Once a provider is selected, the resource is created on that provider through the Service Provider Manager.

Local Setup