fabric-orchestrator/README.md

# Fabric Orchestrator

**Declarative Network Infrastructure Management for Arista EVPN-VXLAN Fabrics**

A workflow-based orchestration system that uses [InfraHub](https://github.com/opsmill/infrahub) as Source of Truth, [Prefect](https://prefect.io) for orchestration, and gNMI/YANG for atomic configuration management of Arista data center fabrics.

## 🎯 Project Vision

Transform network infrastructure management from imperative scripting to true declarative infrastructure-as-code, where:

- **Intent** is defined in InfraHub (custom schema, Git-versioned)
- **Orchestration** is handled by Prefect (Python-native `@flow` and `@task` decorators)
- **State** is continuously monitored via gNMI Subscribe
- **Changes** are computed as diffs and applied atomically via gNMI Set
- **Drift** is detected and optionally auto-remediated

Think `terraform plan` and `terraform apply`, but for your network fabric — powered by Prefect flows.

## 🏗️ Architecture

![architecture](docs/assets/architecture/fabric-orchestration-archi.excalidraw.svg)

## 🎯 Why InfraHub?

We chose [InfraHub](https://github.com/opsmill/infrahub) over NetBox as Source of Truth for several reasons:

| Feature | NetBox | InfraHub |
|---------|--------|----------|
| **Schema** | Fixed DCIM/IPAM model | Fully customizable YAML schema |
| **Git Integration** | External sync needed | Native - branches = data branches |
| **Versioning** | Changelog only | True Git-like versioning with merges |
| **Test/Redeploy** | Dump/restore | `git clone` = complete environment |
| **Transforms** | Limited | Built-in Jinja2 + Python transforms |
| **GraphQL** | Yes | Yes (auto-generated from schema) |

**Key benefits for this project:**

1. **Custom Schema** - Model exactly what we need (VTEPs, MLAG pairs, fabric topology)
2. **Git-native** - Schema + data versioned together, easy test environment setup
3. **Transforms** - Generate device configs directly from InfraHub
4. **Branches** - Test fabric changes in isolated branches before merge

## 📦 Repository as InfraHub Backend

This repository serves as the **single source of truth** for both code and infrastructure data:

```
fabric-orchestrator/
├── .infrahub.yml                 # InfraHub repository config
│
├── schemas/                      # InfraHub schema definitions
│   └── fabric.yml                # Custom EVPN-VXLAN fabric schema
│
├── data/                         # Infrastructure objects (YAML)
│   ├── topology/
│   │   ├── sites.yml
│   │   └── devices.yml           # Spines, Leafs, VTEP pairs
│   ├── network/
│   │   ├── vlans.yml             # VLANs + L2VNI mappings
│   │   ├── vrfs.yml              # VRFs + L3VNI mappings
│   │   └── interfaces.yml        # Interface configs
│   └── routing/
│       ├── bgp_sessions.yml      # Underlay + EVPN overlay
│       └── evpn.yml              # Route targets, RDs
│
├── transforms/                   # Jinja2 templates for config generation
│   └── arista/
│       ├── base.j2
│       ├── interfaces.j2
│       ├── bgp.j2
│       └── evpn.j2
│
└── src/                          # Python orchestration code
```

### Workflow

```bash
# 1. Edit data files (e.g., add a VLAN)
vim data/network/vlans.yml

# 2. Commit & push
git commit -am "Add VLAN 100 for production"
git push

# 3. InfraHub syncs automatically from Git
#    → Data available via GraphQL

# 4. Prefect flow detects change → reconciles fabric
```

### Benefits

- **Reproductibility**: `git clone` → `docker compose up` → complete environment
- **Code Review**: Infrastructure changes go through PR review
- **History**: Full audit trail via Git
- **Testing**: Create a branch, test changes, merge when validated

## 🎛 Why Prefect?

| Feature | Benefit |
|---------|---------|
| **Python-native workflows** | Use `@flow` and `@task` decorators — no YAML, just Python |
| **Free secrets management** | Native `Secret` blocks for credentials (free in OSS) |
| **Built-in UI** | Dashboard, logs, metrics, execution history via `prefect server start` |
| **No containerization required** | Run flows directly with `.serve()` — no Docker needed |
| **Event-driven triggers** | Schedule, webhooks (via FastAPI), flow triggers out of the box |
| **Task dependencies** | Automatic dependency ordering via task result passing or `wait_for` |
| **Retry & error handling** | Built-in retry policies with `@task(retries=3)` |
| **Human-in-the-loop** | Native `pause_flow_run()` for approval workflows |

## 🎯 Target Fabric

This project is designed for the Arista EVPN-VXLAN ContainerLab topology:

- **2 Spines** (BGP Route Reflectors, AS 65000)
- **8 Leafs** (4 MLAG VTEP pairs, AS 65001-65004)
- **cEOS 4.35.0F** with gNMI enabled
- **EVPN Type-2** (L2 VXLAN) and **Type-5** (L3 VXLAN) support

Reference: [arista-evpn-vxlan-clab](https://gitea.arnodo.fr/Damien/arista-evpn-vxlan-clab)

## 📋 Project Phases

Progress is tracked via issues. See [all issues](https://gitea.arnodo.fr/Damien/fabric-orchestrator/issues) or filter by phase:

| Phase | Description | Status |
|-------|-------------|--------|
| **Phase 1** | YANG Path Discovery - Map EOS 4.35.0F YANG models, validate gNMI | ✅ Complete |
| **Phase 2** | InfraHub Setup & Core Reconciler - Schema, diff engine, YANG mappers | 🔄 In Progress |
| **Phase 3** | Full Fabric Coverage - BGP, MLAG, VRFs mappers | 📋 Planned |
| **Phase 4** | Prefect Integration - Flows, webhooks, drift detection | 📋 Planned |

## 📁 Project Structure

```
fabric-orchestrator/
├── README.md
├── pyproject.toml
├── .infrahub.yml                     # InfraHub config (points to schemas/)
│
├── schemas/                          # InfraHub schema definitions
│   └── fabric.yml                    # Custom EVPN-VXLAN fabric schema
│
├── data/                             # Infrastructure data (YAML)
│   ├── topology/
│   │   ├── sites.yml
│   │   └── devices.yml
│   ├── network/
│   │   ├── vlans.yml
│   │   ├── vrfs.yml
│   │   └── interfaces.yml
│   └── routing/
│       ├── bgp_sessions.yml
│       └── evpn.yml
│
├── transforms/                       # Jinja2 config templates
│   └── arista/
│       └── *.j2
│
├── src/                              # Python package
│   ├── __init__.py
│   ├── cli.py                        # CLI for YANG discovery
│   │
│   ├── flows/                        # Prefect flows
│   │   ├── __init__.py
│   │   ├── reconcile.py              # @flow fabric_reconcile
│   │   ├── drift.py                  # @flow handle_drift
│   │   └── remediation.py            # @flow drift_remediation
│   │
│   ├── gnmi/
│   │   ├── __init__.py
│   │   ├── client.py                 # gNMI client wrapper (pygnmi)
│   │   └── README.md
│   │
│   ├── infrahub/                     # InfraHub integration
│   │   ├── __init__.py
│   │   ├── client.py                 # InfraHub SDK wrapper
│   │   └── queries.py                # GraphQL queries
│   │
│   └── yang/
│       ├── __init__.py
│       ├── mapper.py                 # InfraHub intent → YANG paths
│       ├── paths.py                  # YANG path definitions
│       └── mappers/                  # Resource-specific mappers
│           ├── vlan.py
│           ├── interface.py
│           ├── bgp.py
│           └── vxlan.py
│
├── tests/
│
└── docs/
    ├── cli-user-guide.md
    └── yang-paths.md
```

## 🛠️ Technology Stack

| Component | Technology | Purpose |
|-----------|------------|---------|
| Source of Truth | **InfraHub** | Intent definition via custom schema |
| Data Storage | **This Git repo** | Schema + data versioned together |
| Orchestrator | **Prefect** | Python-native workflow orchestration |
| Transport | gNMI | Configuration and telemetry |
| Data Models | YANG (OpenConfig + Arista) | Structured configuration |
| Python Library | pygnmi + infrahub-sdk | gNMI/InfraHub interactions |
| CLI | Click + Rich | YANG discovery tools |
| Validation | Pydantic v2 | Intent data validation |
| Lab | ContainerLab + cEOS | Development environment |

## 🔗 Related Projects

- [arista-evpn-vxlan-clab](https://gitea.arnodo.fr/Damien/arista-evpn-vxlan-clab) - Target fabric topology
- [InfraHub](https://github.com/opsmill/infrahub) - Source of Truth platform
- [InfraHub Schema Library](https://github.com/opsmill/schema-library) - Reference schemas
- [Arista YANG Models](https://github.com/aristanetworks/yang/tree/master/EOS-4.35.0F) - EOS 4.35.0F YANG definitions

## 📚 References

### InfraHub
- [InfraHub Documentation](https://docs.infrahub.app)
- [InfraHub Schema Guide](https://docs.infrahub.app/guides/create-schema)
- [InfraHub Python SDK](https://github.com/opsmill/infrahub-sdk-python)
- [InfraHub .infrahub.yml Reference](https://docs.infrahub.app/reference/dotinfrahub)

### Prefect
- [Prefect Documentation](https://docs.prefect.io)
- [Prefect Flows](https://docs.prefect.io/latest/develop/write-flows/)
- [Prefect Tasks](https://docs.prefect.io/latest/develop/write-tasks/)

### YANG / gNMI
- [Arista gNMI Documentation](https://aristanetworks.github.io/openmgmt/configuration/gnmi/)
- [OpenConfig Models](https://github.com/openconfig/public)
- [pygnmi Library](https://github.com/akarneliuk/pygnmi)

### EVPN-VXLAN
- [Arista BGP EVPN Configuration Example](https://overlaid.net/2019/01/27/arista-bgp-evpn-configuration-example/)

## 🚀 Getting Started

### Prerequisites

- Python 3.12+
- `uv` package manager
- Docker (for InfraHub)
- Access to ContainerLab with cEOS images

### Quick Start

```bash
# Clone the repository (includes schema + data)
git clone https://gitea.arnodo.fr/Damien/fabric-orchestrator.git
cd fabric-orchestrator

# Install Python dependencies
uv sync

# Start InfraHub (loads schema & data from this repo)
docker compose up -d

# Configure Prefect secrets
python -c "
from prefect.blocks.system import Secret
from prefect.variables import Variable

Secret(value='your-gnmi-password').save('gnmi-password', overwrite=True)
Variable.set('infrahub_url', 'http://localhost:8000')
Variable.set('gnmi_username', 'admin')
"

# Verify gNMI connectivity
uv run fabric-orch discover capabilities --target leaf1:6030

# Run reconciliation
uv run fabric-orch plan
uv run fabric-orch apply
```

## Prefect Flow Example

```python
from prefect import flow, task
from prefect.variables import Variable


@task(retries=2, retry_delay_seconds=10)
def get_fabric_intent(device: str | None = None) -> dict:
    """Retrieve fabric intent from InfraHub."""
    from infrahub_sdk import InfrahubClient
    
    client = InfrahubClient(address=Variable.get("infrahub_url"))
    # Query fabric intent via GraphQL
    return client.query(...)


@task
def compute_diff(intent: dict, current: dict) -> list[dict]:
    """Compute diff between desired and current state."""
    from src.reconciler.diff import compute_diff as diff_engine
    return diff_engine(want=intent, have=current)


@flow(log_prints=True, name="fabric-reconcile")
def fabric_reconcile(device: str | None = None, dry_run: bool = True) -> dict:
    """Reconcile fabric state with InfraHub intent."""
    intent = get_fabric_intent(device)
    current = get_current_state(device)
    changes = compute_diff(intent, current)
    
    if not changes:
        print("✅ Fabric is in sync")
        return {"in_sync": True}
    
    if not dry_run:
        apply_changes(changes)
    
    return {"changes": changes, "applied": not dry_run}
```

---

**Status**: 🚧 Active Development - Phase 2 (InfraHub Setup & Core Reconciler)