# ExternalDNS

DNS synchronization (registers/deletes records via the PowerDNS REST API and external cloud DNS APIs where applicable). Per-host-cluster infrastructure (see [`docs/PLATFORM-TECH-STACK.md`](../../docs/PLATFORM-TECH-STACK.md) §3.1) — runs on every host cluster, primarily on the DMZ block. PowerDNS (see [`docs/PLATFORM-POWERDNS.md`](../../docs/PLATFORM-POWERDNS.md)) is the authoritative server for every Sovereign zone; ExternalDNS uses the `webhook` provider (`external-dns-pdns`) to write A/AAAA/CNAME records into PowerDNS. Health-checked geo-failover lives in PowerDNS lua-records — see [`docs/MULTI-REGION-DNS.md`](../../docs/MULTI-REGION-DNS.md).

**Status:** Accepted | **Updated:** 2026-04-27

---

## Overview

ExternalDNS synchronizes Kubernetes resources (Gateway, Service, Ingress) with external DNS providers, enabling automatic DNS record management.

---

## Architecture

```mermaid
flowchart TB
    subgraph K8s["Kubernetes"]
        GW[Gateway API]
        Svc[Services]
        ExtDNS[ExternalDNS]
    end

    subgraph DNS["DNS Providers"]
        PDNS[PowerDNS<br>(authoritative — every Sovereign zone)]
        CF[Cloudflare]
        R53[Route53]
        HDNS[Hetzner DNS]
    end

    GW --> ExtDNS
    Svc --> ExtDNS
    ExtDNS --> PDNS
    ExtDNS --> CF
    ExtDNS --> R53
    ExtDNS --> HDNS
```

---

## Supported DNS Providers

| Provider | Availability |
|----------|--------------|
| Cloudflare | Always |
| Hetzner DNS | If Hetzner chosen |
| AWS Route53 | If AWS chosen |
| GCP Cloud DNS | If GCP chosen |
| Azure DNS | If Azure chosen |

---

## Configuration

### ExternalDNS Deployment

```yaml
apiVersion: apps/v1
kind: Deployment
metadata:
  name: external-dns
  namespace: external-dns
spec:
  template:
    spec:
      containers:
        - name: external-dns
          image: registry.k8s.io/external-dns/external-dns:v0.14.0
          args:
            - --source=gateway-httproute
            - --source=gateway-grpcroute
            - --source=service
            - --provider=cloudflare
            - --cloudflare-proxied
            - --txt-owner-id=openova
            - --txt-prefix=_externaldns.
          env:
            - name: CF_API_TOKEN
              valueFrom:
                secretKeyRef:
                  name: cloudflare-credentials
                  key: api-token
```

---

## PowerDNS Integration (geo + health-checked failover)

ExternalDNS writes plain A/AAAA/CNAME records into PowerDNS via the REST API. Geo-aware and health-checked failover responses are owned by PowerDNS lua-records, written by the `catalyst-dns` controller — ExternalDNS does NOT manage lua-record content.

```mermaid
flowchart LR
    subgraph Region1["Region 1"]
        App1[Application]
        ExtDNS1[ExternalDNS]
    end

    subgraph Region2["Region 2"]
        App2[Application]
        ExtDNS2[ExternalDNS]
    end

    subgraph PDNS["PowerDNS Authoritative"]
        ZoneAPI[REST API]
        Lua[lua-records (ifurlup, pickclosest)]
    end

    ExtDNS1 -->|"plain A/AAAA"| ZoneAPI
    ExtDNS2 -->|"plain A/AAAA"| ZoneAPI
    ZoneAPI --- Lua
```

See [`docs/MULTI-REGION-DNS.md`](../../docs/MULTI-REGION-DNS.md) for the lua-record patterns.

---

## Record Types

| Source | Record Type | Example |
|--------|-------------|---------|
| Gateway | A/CNAME | `api.<domain>` |
| Service (LoadBalancer) | A | `svc.<domain>` |
| catalyst-dns (lua-record author) | LUA A | `app.<domain>` (geo + health-checked) |

---

## TXT Registry

ExternalDNS uses TXT records to track ownership:

```
_externaldns.api.<domain> TXT "heritage=external-dns,external-dns/owner=openova"
```

This prevents ExternalDNS from modifying records it doesn't own.

---

*Part of [OpenOva](https://openova.io)*
