Using unique unit host-alias on /etc/hosts

lib/charms/data_platform_libs/v0/data_interfaces.py

@@ -331,7 +331,7 @@ def _on_topic_requested(self, event: TopicRequestedEvent):
 
 # Increment this PATCH version before using `charmcraft publish-lib` or reset
 # to 0 if you are raising the major API version
-LIBPATCH = 34
+LIBPATCH = 35
 
 PYDEPS = ["ops>=2.0.0"]
 
@@ -2277,7 +2277,7 @@ def __init__(
 
 
 ################################################################################
-# Cross-charm Relatoins Data Handling and Evenets
+# Cross-charm Relations Data Handling and Events
 ################################################################################
 
 # Generic events
@@ -2300,7 +2300,7 @@ class RelationEventWithSecret(RelationEvent):
 
     @property
     def _secrets(self) -> dict:
-        """Caching secrets to avoid fetching them each time a field is referrd.
+        """Caching secrets to avoid fetching them each time a field is referred.
 
         DON'T USE the encapsulated helper variable outside of this function
         """
@@ -2309,7 +2309,7 @@ def _secrets(self) -> dict:
         return self._cached_secrets
 
     def _get_secret(self, group) -> Optional[Dict[str, str]]:
-        """Retrieveing secrets."""
+        """Retrieving secrets."""
         if not self.app:
             return
         if not self._secrets.get(group):
@@ -2498,6 +2498,17 @@ def version(self) -> Optional[str]:
 
         return self.relation.data[self.relation.app].get("version")
 
+    @property
+    def hostname_mapping(self) -> Optional[str]:
+        """Returns the hostname mapping.
+
+        A list that maps the hostnames to IP address.
+        """
+        if not self.relation.app:
+            return None
+
+        return self.relation.data[self.relation.app].get("hostname-mapping")
+
 
 class DatabaseCreatedEvent(AuthenticationEvent, DatabaseRequiresEvent):
     """Event emitted when a new database is created for use on this relation."""
@@ -2602,6 +2613,15 @@ def set_version(self, relation_id: int, version: str) -> None:
         """
         self.update_relation_data(relation_id, {"version": version})
 
+    def set_hostname_mapping(self, relation_id: int, hostname_mapping: list[dict]) -> None:
+        """Set hostname mapping.
+
+        Args:
+            relation_id: the identifier for a particular relation.
+            hostname_mapping: list of hostname mapping.
+        """
+        self.update_relation_data(relation_id, {"hostname-mapping": json.dumps(hostname_mapping)})
+
 
 class DatabaseProviderEventHandlers(EventHandlers):
     """Provider-side of the database relation handlers."""
@@ -3016,7 +3036,7 @@ class KafkaRequiresEvents(CharmEvents):
 # Kafka Provides and Requires
 
 
-class KafkaProvidesData(ProviderData):
+class KafkaProviderData(ProviderData):
     """Provider-side of the Kafka relation."""
 
     def __init__(self, model: Model, relation_name: str) -> None:
@@ -3059,12 +3079,12 @@ def set_zookeeper_uris(self, relation_id: int, zookeeper_uris: str) -> None:
         self.update_relation_data(relation_id, {"zookeeper-uris": zookeeper_uris})
 
 
-class KafkaProvidesEventHandlers(EventHandlers):
+class KafkaProviderEventHandlers(EventHandlers):
     """Provider-side of the Kafka relation."""
 
     on = KafkaProvidesEvents()  # pyright: ignore [reportAssignmentType]
 
-    def __init__(self, charm: CharmBase, relation_data: KafkaProvidesData) -> None:
+    def __init__(self, charm: CharmBase, relation_data: KafkaProviderData) -> None:
         super().__init__(charm, relation_data)
         # Just to keep lint quiet, can't resolve inheritance. The same happened in super().__init__() above
         self.relation_data = relation_data
@@ -3086,15 +3106,15 @@ def _on_relation_changed_event(self, event: RelationChangedEvent) -> None:
             )
 
 
-class KafkaProvides(KafkaProvidesData, KafkaProvidesEventHandlers):
+class KafkaProvides(KafkaProviderData, KafkaProviderEventHandlers):
     """Provider-side of the Kafka relation."""
 
     def __init__(self, charm: CharmBase, relation_name: str) -> None:
-        KafkaProvidesData.__init__(self, charm.model, relation_name)
-        KafkaProvidesEventHandlers.__init__(self, charm, self)
+        KafkaProviderData.__init__(self, charm.model, relation_name)
+        KafkaProviderEventHandlers.__init__(self, charm, self)
 
 
-class KafkaRequiresData(RequirerData):
+class KafkaRequirerData(RequirerData):
     """Requirer-side of the Kafka relation."""
 
     def __init__(
@@ -3124,12 +3144,12 @@ def topic(self, value):
         self._topic = value
 
 
-class KafkaRequiresEventHandlers(RequirerEventHandlers):
+class KafkaRequirerEventHandlers(RequirerEventHandlers):
     """Requires-side of the Kafka relation."""
 
     on = KafkaRequiresEvents()  # pyright: ignore [reportAssignmentType]
 
-    def __init__(self, charm: CharmBase, relation_data: KafkaRequiresData) -> None:
+    def __init__(self, charm: CharmBase, relation_data: KafkaRequirerData) -> None:
         super().__init__(charm, relation_data)
         # Just to keep lint quiet, can't resolve inheritance. The same happened in super().__init__() above
         self.relation_data = relation_data
@@ -3188,7 +3208,7 @@ def _on_relation_changed_event(self, event: RelationChangedEvent) -> None:
             return
 
 
-class KafkaRequires(KafkaRequiresData, KafkaRequiresEventHandlers):
+class KafkaRequires(KafkaRequirerData, KafkaRequirerEventHandlers):
     """Provider-side of the Kafka relation."""
 
     def __init__(
@@ -3200,7 +3220,7 @@ def __init__(
         consumer_group_prefix: Optional[str] = None,
         additional_secret_fields: Optional[List[str]] = [],
     ) -> None:
-        KafkaRequiresData.__init__(
+        KafkaRequirerData.__init__(
             self,
             charm.model,
             relation_name,
@@ -3209,7 +3229,7 @@ def __init__(
             consumer_group_prefix,
             additional_secret_fields,
         )
-        KafkaRequiresEventHandlers.__init__(self, charm, self)
+        KafkaRequirerEventHandlers.__init__(self, charm, self)
 
 
 # Opensearch related events

lib/charms/mysql/v0/async_replication.py

@@ -8,6 +8,7 @@
 import typing
 import uuid
 from functools import cached_property
+from time import sleep
 
 from charms.mysql.v0.mysql import (
     MySQLFencingWritesError,
@@ -221,17 +222,21 @@ def on_async_relation_broken(self, event):  # noqa: C901
             # reset flag to allow instances rejoining the cluster
             self._charm.unit_peer_data["member-state"] = "waiting"
             del self._charm.unit_peer_data["unit-initialized"]
-            if self._charm.unit.is_leader():
-                self._charm.app.status = BlockedStatus("Recreate or rejoin cluster.")
-                logger.info(
-                    "\n\tThis is a replica cluster and will be dissolved.\n"
-                    "\tThe cluster can be recreated with the `recreate-cluster` action.\n"
-                    "\tAlternatively the cluster can be rejoined to the cluster set."
-                )
-                # reset the cluster node count flag
-                del self._charm.app_peer_data["units-added-to-cluster"]
-                # set flag to persist removed from cluster-set state
-                self._charm.app_peer_data["removed-from-cluster-set"] = "true"
+            if not self._charm.unit.is_leader():
+                # delay non leader to avoid `update_status` running before
+                # leader updates app peer data
+                sleep(10)
+                return
+            self._charm.app.status = BlockedStatus("Recreate or rejoin cluster.")
+            logger.info(
+                "\n\tThis is a replica cluster and will be dissolved.\n"
+                "\tThe cluster can be recreated with the `recreate-cluster` action.\n"
+                "\tAlternatively the cluster can be rejoined to the cluster set."
+            )
+            # reset the cluster node count flag
+            del self._charm.app_peer_data["units-added-to-cluster"]
+            # set flag to persist removed from cluster-set state
+            self._charm.app_peer_data["removed-from-cluster-set"] = "true"
 
         elif self.role.cluster_role == "primary":
             if self._charm.unit.is_leader():

lib/charms/mysql/v0/mysql.py

@@ -116,7 +116,7 @@ def wait_until_mysql_connection(self) -> None:
 
 # Increment this PATCH version before using `charmcraft publish-lib` or reset
 # to 0 if you are raising the major API version
-LIBPATCH = 58
+LIBPATCH = 59
 
 UNIT_TEARDOWN_LOCKNAME = "unit-teardown"
 UNIT_ADD_LOCKNAME = "unit-add"
@@ -1361,7 +1361,7 @@ def create_replica_cluster(
             "communicationStack": "MySQL",
         }
 
-        if donor:
+        if donor and method == "clone":
             options["cloneDonor"] = donor
 
         commands = (

pyproject.toml

@@ -17,6 +17,7 @@ boto3 = "^1.28.23"
 pyopenssl = "^24.0.0"
 typing_extensions = "^4.7.1"
 jinja2 = "^3.1.2"
+python-hosts = "^1.0.6"
 
 [tool.poetry.group.charm-libs.dependencies]
 # data_platform_libs/v0/data_interfaces.py

src/charm.py

@@ -288,6 +288,9 @@ def _on_start(self, event: StartEvent) -> None:
 
         self.unit.status = MaintenanceStatus("Setting up cluster node")
 
+        if not self.hostname_resolution.is_unit_in_hosts:
+            self.hostname_resolution.update_etc_hosts(None)
+
         try:
             self.workload_initialise()
         except MySQLConfigureMySQLUsersError:
@@ -526,7 +529,7 @@ def _on_cos_agent_relation_broken(self, event: RelationBrokenEvent) -> None:
     def _mysql(self):
         """Returns an instance of the MySQL object."""
         return MySQL(
-            self.unit_fqdn,
+            self.unit_host_alias,
             self.app_peer_data["cluster-name"],
             self.app_peer_data["cluster-set-domain-name"],
             self.get_secret("app", ROOT_PASSWORD_KEY),  # pyright: ignore [reportArgumentType]
@@ -562,6 +565,14 @@ def unit_fqdn(self) -> str:
         """Returns the unit's FQDN."""
         return socket.getfqdn()
 
+    @property
+    def unit_host_alias(self) -> str:
+        """Returns the unit's host alias.
+
+        The format is <unit_label>.<model_uuid>
+        """
+        return self.unit_label + "." + self.model.uuid
+
     @property
     def restart_peers(self) -> Optional[ops.model.Relation]:
         """Retrieve the peer relation."""