Migrate cassandra client to database manager.

Author: Zvirovyi

src/charm.py

@@ -16,6 +16,7 @@
 from events.cassandra import CassandraEvents
 from managers.cluster import ClusterManager
 from managers.config import ConfigManager
+from managers.database import DatabaseManager
 from workload import CassandraWorkload
 
 logger = logging.getLogger(__name__)
@@ -40,6 +41,15 @@ def __init__(self, *args):
             seeds=self.state.cluster.seeds,
             authentication=bool(self.state.cluster.cassandra_password_secret),
         )
+        database_manager = DatabaseManager(
+            hosts=[
+                "127.0.0.1"
+                if self.state.unit.workload_state == UnitWorkloadState.CHANGING_PASSWORD
+                else self.state.unit.ip
+            ],
+            user="cassandra",
+            password=self.state.cluster.cassandra_password_secret,
+        )
         bootstrap_manager = RollingOpsManager(
             charm=self, relation="bootstrap", callback=self.bootstrap
         )
@@ -50,6 +60,7 @@ def __init__(self, *args):
             workload=self.workload,
             cluster_manager=self.cluster_manager,
             config_manager=config_manager,
+            database_manager=database_manager,
             bootstrap_manager=bootstrap_manager,
         )
 

src/events/cassandra.py

@@ -18,13 +18,13 @@
 )
 from pydantic import ValidationError
 
-from common.cassandra_client import CassandraClient
 from core.config import CharmConfig
 from core.state import ApplicationState, UnitWorkloadState
 from core.statuses import Status
 from core.workload import WorkloadBase
 from managers.cluster import ClusterManager
 from managers.config import ConfigManager
+from managers.database import DatabaseManager
 
 logger = logging.getLogger(__name__)
 
@@ -40,6 +40,7 @@ def __init__(
         cluster_manager: ClusterManager,
         config_manager: ConfigManager,
         bootstrap_manager: RollingOpsManager,
+        database_manager: DatabaseManager,
     ):
         super().__init__(charm, key="cassandra_events")
         self.charm = charm
@@ -48,6 +49,7 @@ def __init__(
         self.cluster_manager = cluster_manager
         self.config_manager = config_manager
         self.bootstrap_manager = bootstrap_manager
+        self.database_manager = database_manager
 
         self.framework.observe(self.charm.on.start, self._on_start)
         self.framework.observe(self.charm.on.install, self._on_install)
@@ -112,7 +114,7 @@ def _finalize_password_change(self, event: StartEvent) -> None:
             event.defer()
             return
         password = self.workload.generate_password()
-        self._cassandra.change_superuser_password("cassandra", password)
+        self.database_manager.update_system_user_password("cassandra", password)
         self.state.cluster.cassandra_password_secret = password
         self.cluster_manager.flush_tables("system_auth", ["roles"])
         self.config_manager.render_cassandra_config(
@@ -205,11 +207,3 @@ def _update_network_address(self) -> bool:
             and old_hostname is not None
             and (old_ip != self.state.unit.ip or old_hostname != self.state.unit.hostname)
         )
-
-    @property
-    def _cassandra(self) -> CassandraClient:
-        return CassandraClient(
-            [self.state.unit.ip if self.state.cluster.cassandra_password_secret else "127.0.0.1"],
-            "cassandra",
-            self.state.cluster.cassandra_password_secret or None,
-        )

src/managers/cluster.py

@@ -20,7 +20,6 @@ class ClusterManager:
 
     def __init__(self, workload: WorkloadBase):
         self._workload = workload
-        pass
 
     @property
     def is_healthy(self) -> bool:
@@ -37,5 +36,5 @@ def network_address(self) -> tuple[str, str]:
         return socket.gethostbyname(hostname), hostname
 
     def flush_tables(self, keyspace: str, tables: list[str]) -> None:
-        """TODO."""
+        """Flush tables in keyspace to disk."""
         self._workload.exec(["charmed-cassandra.nodetool", "flush", keyspace, *tables])

src/common/cassandra_client.py renamed to src/managers/database.py

@@ -2,7 +2,7 @@
 # Copyright 2025 Canonical Ltd.
 # See LICENSE file for licensing details.
 
-"""Cassandra CQL client."""
+"""Database manager."""
 
 import logging
 from contextlib import contextmanager
@@ -16,24 +16,22 @@
 logger = logging.getLogger(__name__)
 
 
-class CassandraClient:
-    """Cassandra CQL client."""
+class DatabaseManager:
+    """Manager of Cassandra database."""
 
-    def __init__(self, hosts: list[str], user: str | None = None, password: str | None = None):
+    def __init__(self, hosts: list[str], user: str, password: str):
         self.execution_profile = ExecutionProfile(
             load_balancing_policy=TokenAwarePolicy(DCAwareRoundRobinPolicy())
         )
         self.auth_provider = (
-            PlainTextAuthProvider(username=user, password=password)
-            if user is not None and password is not None
-            else None
+            PlainTextAuthProvider(username=user, password=password) if user and password else None
         )
         self.hosts = hosts
 
         return
 
-    def change_superuser_password(self, user: str, password: str) -> None:
-        """TODO."""
+    def update_system_user_password(self, user: str, password: str) -> None:
+        """Change password for the role in system_auth."""
         with self._session() as session:
             session.execute(
                 "UPDATE system_auth.roles SET salted_hash = %s WHERE role = %s",
@@ -43,11 +41,6 @@ def change_superuser_password(self, user: str, password: str) -> None:
                 ],
             )
 
-    def change_user_password(self, user: str, password: str) -> None:
-        """TODO."""
-        with self._session() as session:
-            session.execute("ALTER USER %s WITH PASSWORD %s", [user, password])
-
     @contextmanager
     def _session(self, keyspace: str | None = None) -> Generator[Session, None, None]:
         cluster = Cluster(