Architecture Overview

DCM (Data Center Management) is a control plane for managing infrastructure services across multiple environment agents. 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"]
        AM["Agent Manager"]
        RM["SP Resource Manager"]
    end

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

    subgraph Agents
        EA1["Environment Agent 1"]
        EA2["Environment Agent 2"]
    end

    User --> CP

    CM --> PG
    PM --> PG
    PLM --> PG
    AM --> PG
    RM --> PG

    PLM --> PM
    PLM --> AM
    CM --> PLM

    RM --> NATS
    EA1 --> NATS
    EA2 --> NATS
    EA1 -->|register| AM
    EA2 -->|register| AM

Component Responsibilities

Component	Role
Control Plane	Single process that exposes all DCM APIs on `:8080`. Hosts the catalog, policy, placement, agent, and SP resource 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 an environment agent for a new instance by evaluating policies against available agents.
Agent Manager	Tracks registered environment agents and their health status.
SP Resource Manager	Manages the lifecycle of resources on service providers through environment agents.
PostgreSQL	Persistent storage for the control plane.
NATS	Message bus for communication between the SP Resource Manager and environment agents.
Environment Agents	Agents that bridge the control plane and service providers (e.g., KubeVirt). They register with the control plane 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 RM as SP Resource Manager
    participant EA as Environment Agent
    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 (selected agent)
    PLM->>RM: Create resource on agent
    RM->>EA: Provision via NATS
    EA->>SP: Create VM
    SP-->>User: VM scheduling

The Catalog Manager receives the request and asks the Placement Manager to find a suitable agent.
The Placement Manager evaluates placement policies through the Policy Manager, which uses an embedded OPA engine to evaluate Rego.
Once an agent is selected, the resource is created through the SP Resource Manager, which sends the request to the environment agent via NATS. The agent provisions the resource on the underlying service provider.

Local Setup