fix: update maas_url when region goes down

maas-region/charmcraft.yaml

@@ -133,3 +133,10 @@ config:
       default: ""
       description: Whether to enable TLS termination at HA Proxy ('termination'), or no TLS ('')
       type: string
+    maas_url:
+      default: ""
+      description: |
+        The maas_url to set. If not provided, the maas_url is formulated by the IP of maas-region
+        leader and MAAS API port. If application is related to HAProxy, the proxy port is used
+        instead.
+      type: string

maas-region/src/charm.py

@@ -69,6 +69,7 @@ def __init__(self, *args):
         self.framework.observe(self.on.remove, self._on_remove)
         self.framework.observe(self.on.start, self._on_start)
         self.framework.observe(self.on.collect_unit_status, self._on_collect_status)
+        self.framework.observe(self.on.leader_elected, self._on_leader_elected)
 
         # MAAS Region
         self.maas_region = maas.MaasRegionProvider(self)
@@ -175,13 +176,16 @@ def maas_api_url(self) -> str:
         Returns:
             str: The API URL
         """
-        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 ""
+        if maas_url := self.config["maas_url"]:
+            return str(maas_url)
+        if self.model.unit.is_leader() and (bind := self.bind_address):
+            if self.model.get_relation(MAAS_API_RELATION):
+                port = MAAS_PROXY_PORT
+            else:
+                port = MAAS_HTTP_PORT
+            return f"http://{bind}:{port}/MAAS"
+        else:
+            return self.get_peer_data(self.app, "maas_url")
 
     @property
     def maas_id(self) -> Union[str, None]:
@@ -230,9 +234,25 @@ def _setup_network(self) -> bool:
         return True
 
     def _initialize_maas(self) -> bool:
+        if (
+            maas_details := MaasHelper.get_maas_details()
+        ) and self.get_operational_mode() == MaasHelper.get_maas_mode():
+            u, p, h, d = (
+                maas_details["database_user"],
+                maas_details["database_pass"],
+                maas_details["database_host"],
+                maas_details["database_name"],
+            )
+            if (
+                self.get_peer_data(self.app, "maas_url") == maas_details["maas_url"]
+                and f"postgres://{u}:{p}@{h}/{d}" == self.connection_string
+            ):
+                return True
         try:
             MaasHelper.setup_region(
-                self.maas_api_url, self.connection_string, self.get_operational_mode()
+                self.get_peer_data(self.app, "maas_url"),
+                self.connection_string,
+                self.get_operational_mode(),
             )
             return True
         except subprocess.CalledProcessError:
@@ -313,9 +333,10 @@ def _on_install(self, _event: ops.InstallEvent) -> None:
             event (ops.InstallEvent): Event from ops framework
         """
         self.unit.status = ops.MaintenanceStatus("installing...")
-        channel = str(self.config.get("channel", MAAS_SNAP_CHANNEL))
+        if self.unit.is_leader():
+            self.set_peer_data(self.app, "maas_url", "")
         try:
-            MaasHelper.install(channel)
+            MaasHelper.install(MAAS_SNAP_CHANNEL)
         except Exception as ex:
             logger.error(str(ex))
 
@@ -343,6 +364,12 @@ def _on_collect_status(self, e: ops.CollectStatusEvent) -> None:
         else:
             self.unit.status = ops.ActiveStatus()
 
+    def _on_leader_elected(self, e: ops.LeaderElectedEvent) -> None:
+        maas_url = self.maas_api_url
+        if self.get_peer_data(self.app, "maas_url") != maas_url:
+            self.set_peer_data(self.app, "maas_url", maas_url)
+            self._initialize_maas()
+
     def _on_maasdb_created(self, event: db.DatabaseCreatedEvent) -> None:
         """Database is ready.
 
@@ -377,6 +404,7 @@ def _on_maas_peer_changed(self, event: ops.RelationEvent) -> None:
         self.set_peer_data(self.unit, "system-name", socket.getfqdn())
         if self.unit.is_leader():
             self._publish_tokens()
+        self._initialize_maas()
 
     def _on_maas_cluster_changed(self, event: ops.RelationEvent) -> None:
         logger.info(event)
@@ -439,6 +467,14 @@ def _on_config_changed(self, event: ops.ConfigChangedEvent):
             msg = f"Invalid tls_mode configuration: '{tls_mode}'. Valid options are: {self._TLS_MODES}"
             self.unit.status = ops.BlockedStatus(msg)
             raise ValueError(msg)
+
+        if maas_url := self.config["maas_url"]:
+            if self.unit.is_leader():
+                maas_url = self.maas_api_url
+                if self.get_peer_data(self.app, "maas_url") != maas_url:
+                    self.set_peer_data(self.app, "maas_url", maas_url)
+                    self._initialize_maas()
+
         self._update_ha_proxy()
 
 

maas-region/src/helper.py

@@ -5,14 +5,16 @@
 
 import subprocess
 from pathlib import Path
-from typing import Union
+from typing import Dict, Union
 
+import yaml
 from charms.operator_libs_linux.v2.snap import SnapCache, SnapState
 
 MAAS_SNAP_NAME = "maas"
 MAAS_MODE = Path("/var/snap/maas/common/snap_mode")
 MAAS_SECRET = Path("/var/snap/maas/common/maas/secret")
 MAAS_ID = Path("/var/snap/maas/common/maas/maas_id")
+MAAS_CONF = Path("/var/snap/maas/current/regiond.conf")
 MAAS_SERVICE = "pebble"
 
 
@@ -84,6 +86,19 @@ def get_maas_mode() -> Union[str, None]:
         except OSError:
             return None
 
+    @staticmethod
+    def get_maas_details() -> Dict[str, str]:
+        """Get MAAS operation mode.
+
+        Returns:
+            Dict[str, str]: MAAS details
+        """
+        try:
+            with MAAS_CONF.open() as file:
+                return yaml.safe_load(file)
+        except (OSError, yaml.YAMLError):
+            return {}
+
     @staticmethod
     def is_running() -> bool:
         """Check if MAAS is running.