feat: add peer sync worker for zone_data exchange between nodes 🔄

Adds optional peer-to-peer zone_data replication between directdnsonly
instances. Enables eventual consistency in DA Multi-Server topologies
without a shared datastore.

- InternalAPI: GET /internal/zones (list) and ?domain= (detail)
  exposes zone_data to peers via existing basic auth
- PeerSyncWorker: interval-based daemon thread that fetches zone_data
  from configured peers, storing newer entries locally; peer downtime
  is silently skipped and retried next interval
- WorkerManager: wires PeerSyncWorker alongside reconciler; exposes
  peer_syncer_alive in queue_status
- Config: peer_sync block with enabled/interval_minutes/peers[]
- Tests: 13 tests covering sync, skip-older, skip-unreachable, empty
  peer list, bad status, and missing zone_data scenarios

tests/conftest.py

@@ -37,4 +37,5 @@ def patch_connect(db_session, monkeypatch):
     _factory = lambda: db_session  # noqa: E731
     monkeypatch.setattr("directdnsonly.app.utils.connect", _factory)
     monkeypatch.setattr("directdnsonly.app.reconciler.connect", _factory)
+    monkeypatch.setattr("directdnsonly.app.peer_sync.connect", _factory)
     return db_session

tests/test_peer_sync.py

@@ -0,0 +1,251 @@
+"""Tests for directdnsonly.app.peer_sync — PeerSyncWorker."""
+
+import datetime
+import json
+import pytest
+from unittest.mock import patch, MagicMock
+
+from directdnsonly.app.peer_sync import PeerSyncWorker
+from directdnsonly.app.db.models import Domain
+
+
+# ---------------------------------------------------------------------------
+# Fixtures
+# ---------------------------------------------------------------------------
+
+BASE_CONFIG = {
+    "enabled": True,
+    "interval_minutes": 15,
+    "peers": [
+        {
+            "url": "http://ddo-2:2222",
+            "username": "directdnsonly",
+            "password": "changeme",
+        }
+    ],
+}
+
+NOW = datetime.datetime(2024, 6, 1, 12, 0, 0)
+OLDER = datetime.datetime(2024, 6, 1, 11, 0, 0)
+
+ZONE_DATA = "$ORIGIN example.com.\n@ 300 IN SOA ns1 hostmaster 1 3600 900 604800 300\n"
+
+
+# ---------------------------------------------------------------------------
+# Config / startup tests
+# ---------------------------------------------------------------------------
+
+
+def test_disabled_by_default():
+    worker = PeerSyncWorker({})
+    assert not worker.enabled
+
+
+def test_interval_stored():
+    worker = PeerSyncWorker({"enabled": True, "interval_minutes": 30})
+    assert worker.interval_seconds == 1800
+
+
+def test_default_interval():
+    worker = PeerSyncWorker({"enabled": True})
+    assert worker.interval_seconds == 15 * 60
+
+
+def test_peers_stored():
+    worker = PeerSyncWorker(BASE_CONFIG)
+    assert len(worker.peers) == 1
+    assert worker.peers[0]["url"] == "http://ddo-2:2222"
+
+
+def test_start_skips_when_disabled(caplog):
+    worker = PeerSyncWorker({"enabled": False})
+    worker.start()
+    assert worker._thread is None
+
+
+def test_start_warns_when_no_peers(caplog):
+    import logging
+    worker = PeerSyncWorker({"enabled": True, "peers": []})
+    with patch.object(worker, "_run"):
+        worker.start()
+    # Thread should not have started
+    assert worker._thread is None
+
+
+# ---------------------------------------------------------------------------
+# _sync_from_peer tests
+# ---------------------------------------------------------------------------
+
+
+def _make_peer():
+    return BASE_CONFIG["peers"][0]
+
+
+def _peer_list(domain, ts=None):
+    """Simulate the JSON response from GET /internal/zones."""
+    return [
+        {
+            "domain": domain,
+            "zone_updated_at": ts.isoformat() if ts else None,
+            "hostname": "da1.example.com",
+            "username": "admin",
+        }
+    ]
+
+
+def _peer_zone(domain, ts=None, zone_data=ZONE_DATA):
+    """Simulate the JSON response from GET /internal/zones?domain=X."""
+    return {
+        "domain": domain,
+        "zone_data": zone_data,
+        "zone_updated_at": ts.isoformat() if ts else None,
+        "hostname": "da1.example.com",
+        "username": "admin",
+    }
+
+
+def test_sync_creates_new_local_record(patch_connect, monkeypatch):
+    """When local DB has no record, peer zone_data is fetched and stored."""
+    worker = PeerSyncWorker(BASE_CONFIG)
+    session = patch_connect
+
+    def mock_get(url, auth=None, timeout=10, params=None):
+        resp = MagicMock()
+        resp.status_code = 200
+        if params and params.get("domain"):
+            resp.json.return_value = _peer_zone("example.com", NOW)
+        else:
+            resp.json.return_value = _peer_list("example.com", NOW)
+        return resp
+
+    monkeypatch.setattr("directdnsonly.app.peer_sync.requests.get", mock_get)
+
+    worker._sync_from_peer(_make_peer())
+
+    record = session.query(Domain).filter_by(domain="example.com").first()
+    assert record is not None
+    assert record.zone_data == ZONE_DATA
+    assert record.zone_updated_at == NOW
+
+
+def test_sync_updates_older_local_record(patch_connect, monkeypatch):
+    """When local zone_data is older than peer's, it is overwritten."""
+    session = patch_connect
+    session.add(Domain(domain="example.com", zone_data="old data", zone_updated_at=OLDER))
+    session.commit()
+
+    worker = PeerSyncWorker(BASE_CONFIG)
+
+    def mock_get(url, auth=None, timeout=10, params=None):
+        resp = MagicMock()
+        resp.status_code = 200
+        if params and params.get("domain"):
+            resp.json.return_value = _peer_zone("example.com", NOW)
+        else:
+            resp.json.return_value = _peer_list("example.com", NOW)
+        return resp
+
+    monkeypatch.setattr("directdnsonly.app.peer_sync.requests.get", mock_get)
+
+    worker._sync_from_peer(_make_peer())
+
+    record = session.query(Domain).filter_by(domain="example.com").first()
+    assert record.zone_data == ZONE_DATA
+    assert record.zone_updated_at == NOW
+
+
+def test_sync_skips_when_local_is_newer(patch_connect, monkeypatch):
+    """When local zone_data is newer than peer's, it is not overwritten."""
+    session = patch_connect
+    session.add(Domain(domain="example.com", zone_data="newer local", zone_updated_at=NOW))
+    session.commit()
+
+    worker = PeerSyncWorker(BASE_CONFIG)
+    fetch_calls = []
+
+    def mock_get(url, auth=None, timeout=10, params=None):
+        resp = MagicMock()
+        resp.status_code = 200
+        if params and params.get("domain"):
+            fetch_calls.append(url)
+            resp.json.return_value = _peer_zone("example.com", OLDER)
+        else:
+            resp.json.return_value = _peer_list("example.com", OLDER)
+        return resp
+
+    monkeypatch.setattr("directdnsonly.app.peer_sync.requests.get", mock_get)
+
+    worker._sync_from_peer(_make_peer())
+
+    # zone_data fetch should not have been called
+    assert not fetch_calls
+    record = session.query(Domain).filter_by(domain="example.com").first()
+    assert record.zone_data == "newer local"
+
+
+def test_sync_skips_unreachable_peer(monkeypatch):
+    """If the peer raises a connection error, _sync_all catches it gracefully."""
+    worker = PeerSyncWorker(BASE_CONFIG)
+
+    def mock_get(*args, **kwargs):
+        raise ConnectionError("peer down")
+
+    monkeypatch.setattr("directdnsonly.app.peer_sync.requests.get", mock_get)
+
+    # Should not raise
+    worker._sync_all()
+
+
+def test_sync_skips_peer_with_bad_status(patch_connect, monkeypatch):
+    """Non-200 response from peer zone list is silently skipped."""
+    worker = PeerSyncWorker(BASE_CONFIG)
+    session = patch_connect
+
+    def mock_get(url, auth=None, timeout=10, params=None):
+        resp = MagicMock()
+        resp.status_code = 503
+        return resp
+
+    monkeypatch.setattr("directdnsonly.app.peer_sync.requests.get", mock_get)
+
+    worker._sync_from_peer(_make_peer())
+
+    # No records should have been created
+    assert session.query(Domain).count() == 0
+
+
+def test_sync_skips_missing_zone_data_in_response(patch_connect, monkeypatch):
+    """If the peer returns no zone_data for a domain, it is skipped."""
+    session = patch_connect
+
+    worker = PeerSyncWorker(BASE_CONFIG)
+
+    def mock_get(url, auth=None, timeout=10, params=None):
+        resp = MagicMock()
+        resp.status_code = 200
+        if params and params.get("domain"):
+            resp.json.return_value = {"domain": "example.com", "zone_data": None}
+        else:
+            resp.json.return_value = _peer_list("example.com", NOW)
+        return resp
+
+    monkeypatch.setattr("directdnsonly.app.peer_sync.requests.get", mock_get)
+
+    worker._sync_from_peer(_make_peer())
+
+    assert session.query(Domain).count() == 0
+
+
+def test_sync_empty_peer_list(patch_connect, monkeypatch):
+    """Empty zone list from peer results in zero syncs without error."""
+    worker = PeerSyncWorker(BASE_CONFIG)
+
+    def mock_get(url, auth=None, timeout=10, params=None):
+        resp = MagicMock()
+        resp.status_code = 200
+        resp.json.return_value = []
+        return resp
+
+    monkeypatch.setattr("directdnsonly.app.peer_sync.requests.get", mock_get)
+
+    worker._sync_from_peer(_make_peer())