add HAProxy integration (#9)

maas-region-charm/charmcraft.yaml

@@ -44,6 +44,8 @@ peers:
     interface: maas_peers
 
 provides:
+  api:
+    interface: http
   maas-region:
     interface: maas_controller
   cos-agent:

maas-region-charm/src/charm.py

@@ -11,6 +11,7 @@
 from typing import Any
 
 import ops
+import yaml
 from charms.data_platform_libs.v0 import data_interfaces as db
 from charms.grafana_agent.v0 import cos_agent
 from charms.maas_region_charm.v0 import maas
@@ -19,10 +20,13 @@
 logger = logging.getLogger(__name__)
 
 MAAS_PEER_NAME = "maas-cluster"
+MAAS_API_RELATION = "api"
 MAAS_DB_NAME = "maas-db"
 
 MAAS_SNAP_CHANNEL = "3.4/stable"
 
+MAAS_PROXY_PORT = 80
+
 MAAS_HTTP_PORT = 5240
 MAAS_HTTPS_PORT = 5443
 MAAS_REGION_METRICS_PORT = 5239
@@ -80,6 +84,12 @@ def __init__(self, *args):
         self.framework.observe(self.maasdb.on.database_created, self._on_maasdb_created)
         self.framework.observe(self.maasdb.on.endpoints_changed, self._on_maasdb_endpoints_changed)
 
+        # HAProxy
+        api_events = self.on[MAAS_API_RELATION]
+        self.framework.observe(api_events.relation_changed, self._on_api_endpoint_changed)
+        self.framework.observe(api_events.relation_departed, self._on_api_endpoint_changed)
+        self.framework.observe(api_events.relation_broken, self._on_api_endpoint_changed)
+
         # COS
         self._grafana_agent = cos_agent.COSAgentProvider(
             self,
@@ -138,19 +148,31 @@ def enrollment_token(self) -> str | None:
         """
         return MaasHelper.get_maas_secret()
 
+    @property
+    def bind_address(self) -> str | None:
+        """Get Unit bind address.
+
+        Returns:
+            str: A single address that the charm's application should bind() to.
+        """
+        if bind := self.model.get_binding("juju-info"):
+            return str(bind.network.bind_address)
+        return None
+
     @property
     def maas_api_url(self) -> str:
         """Get MAAS API URL.
 
         Returns:
             str: The API URL
         """
-        # FIXME use VIP when HAProxy is used
-        if bind := self.model.get_binding("juju-info"):
-            unit_ip = bind.network.bind_address
-            return f"http://{unit_ip}:{MAAS_HTTP_PORT}/MAAS"
-        else:
-            return ""
+        if relation := self.model.get_relation(MAAS_API_RELATION):
+            unit = next(iter(relation.units), None)
+            if unit and (addr := relation.data[unit].get("public-address")):
+                return f"http://{addr}:{MAAS_PROXY_PORT}/MAAS"
+        if bind := self.bind_address:
+            return f"http://{bind}:{MAAS_HTTP_PORT}/MAAS"
+        return ""
 
     @property
     def maas_id(self) -> str | None:
@@ -223,6 +245,27 @@ def _get_regions(self) -> list[str]:
                     eps += [addr]
         return list(set(eps))
 
+    def _update_ha_proxy(self) -> None:
+        if relation := self.model.get_relation(MAAS_API_RELATION):
+            app_name = f"api-{self.app.name}"
+            data = [
+                {
+                    "service_name": "haproxy_service" if MAAS_PROXY_PORT == 80 else app_name,
+                    "service_host": "0.0.0.0",
+                    "service_port": MAAS_PROXY_PORT,
+                    "service_options": ["mode http", "balance leastconn"],
+                    "servers": [
+                        (
+                            f"{app_name}-{self.unit.name.replace('/', '-')}",
+                            self.bind_address,
+                            MAAS_HTTP_PORT,
+                            [],
+                        )
+                    ],
+                }
+            ]
+            relation.data[self.unit]["services"] = yaml.safe_dump(data)
+
     def _on_start(self, _event: ops.StartEvent) -> None:
         """Handle the MAAS controller startup.
 
@@ -296,6 +339,13 @@ def _on_maasdb_endpoints_changed(self, event: db.DatabaseEndpointsChangedEvent)
             logger.info(f"DSN: {conn}")
             self._initialize_maas()
 
+    def _on_api_endpoint_changed(self, event: ops.RelationEvent) -> None:
+        logger.info(event)
+        self._update_ha_proxy()
+        self._initialize_maas()
+        if self.unit.is_leader():
+            self._publish_tokens()
+
     def _on_maas_peer_changed(self, event: ops.RelationEvent) -> None:
         logger.info(event)
         self.set_peer_data(self.unit, "system-name", socket.getfqdn())

maas-region-charm/tests/unit/test_charm.py

@@ -11,7 +11,16 @@
 
 import ops
 import ops.testing
-from charm import MAAS_DB_NAME, MAAS_HTTP_PORT, MAAS_PEER_NAME, MAAS_SNAP_CHANNEL, MaasRegionCharm
+import yaml
+from charm import (
+    MAAS_API_RELATION,
+    MAAS_DB_NAME,
+    MAAS_HTTP_PORT,
+    MAAS_PEER_NAME,
+    MAAS_PROXY_PORT,
+    MAAS_SNAP_CHANNEL,
+    MaasRegionCharm,
+)
 from charms.maas_region_charm.v0 import maas
 
 
@@ -95,6 +104,21 @@ def test_peer_relation_data(self):
         self.harness.charm.set_peer_data(self.harness.charm.app, "test_key", None)
         self.assertEqual(self.harness.get_relation_data(rel_id, app_name)["test_key"], "{}")
 
+    @patch("charm.MaasHelper", autospec=True)
+    def test_ha_proxy_data(self, mock_helper):
+        self.harness.set_leader(True)
+        self.harness.begin()
+        ha = self.harness.add_relation(
+            MAAS_API_RELATION, "haproxy", unit_data={"public-address": "proxy.maas"}
+        )
+
+        ha_data = yaml.safe_load(self.harness.get_relation_data(ha, "maas-region/0")["services"])
+        self.assertEqual(len(ha_data), 1)
+        self.assertIn("service_name", ha_data[0])
+        self.assertIn("service_host", ha_data[0])
+        self.assertEqual(len(ha_data[0]["servers"]), 1)
+        self.assertEqual(ha_data[0]["servers"][0][1], "10.0.0.10")
+
     @patch("charm.MaasHelper", autospec=True)
     def test_on_maas_cluster_changed_new_agent(self, mock_helper):
         mock_helper.get_maas_mode.return_value = "region"
@@ -113,6 +137,25 @@ def test_on_maas_cluster_changed_new_agent(self, mock_helper):
         self.assertEqual(data["regions"], f'["{socket.getfqdn()}"]')
         self.assertIn("maas_secret_id", data)
 
+    @patch(
+        "charm.MaasRegionCharm.connection_string",
+        new_callable=PropertyMock(return_value="postgres://"),
+    )
+    @patch("charm.MaasHelper", autospec=True)
+    def test_ha_proxy_update_api_url(self, mock_helper, _mock_conn_id):
+        mock_helper.get_maas_mode.return_value = "region"
+        mock_helper.get_maas_secret.return_value = "very-secret"
+        self.harness.set_leader(True)
+        self.harness.begin()
+        self.harness.add_relation(
+            MAAS_API_RELATION, "haproxy", unit_data={"public-address": "proxy.maas"}
+        )
+        mock_helper.setup_region.assert_called_once_with(
+            f"http://proxy.maas:{MAAS_PROXY_PORT}/MAAS",
+            "postgres://",
+            "region",
+        )
+
     @patch(
         "charm.MaasRegionCharm.connection_string",
         new_callable=PropertyMock(return_value="postgres://"),