[DPE-2406] Fix pod deletion (#134)

* Fix pod deletion

* Also add fix to on start hook

src/charm.py

@@ -24,6 +24,7 @@
 from ops.pebble import ConnectionError, Layer, PathError, ServiceStatus
 
 from constants import (
+    AUTH_FILE_DATABAG_KEY,
     AUTH_FILE_PATH,
     CLIENT_RELATION_NAME,
     EXTENSIONS_BLOCKING_MESSAGE,
@@ -58,7 +59,9 @@ def __init__(self, *args):
 
         self.framework.observe(self.on.config_changed, self._on_config_changed)
         self.framework.observe(self.on.pgbouncer_pebble_ready, self._on_pgbouncer_pebble_ready)
+        self.framework.observe(self.on.start, self._on_start)
         self.framework.observe(self.on.update_status, self._on_update_status)
+        self.framework.observe(self.on.upgrade_charm, self._on_upgrade_charm)
 
         self.peers = Peers(self)
         self.backend = BackendDatabaseRequires(self)
@@ -279,6 +282,15 @@ def _pgbouncer_layer(self) -> Layer:
             }
         )
 
+    def _on_start(self, _) -> None:
+        """Re-render the auth file, which is lost if the host machine is restarted."""
+        self.render_auth_file_if_available()
+
+    def render_auth_file_if_available(self):
+        """Render the auth file if it's available in the secret store."""
+        if auth_file := self.get_secret("app", AUTH_FILE_DATABAG_KEY):
+            self.render_auth_file(auth_file)
+
     def _on_update_status(self, _) -> None:
         """Update Status hook.
 
@@ -315,6 +327,10 @@ def update_status(self):
             logger.error(not_running)
             self.unit.status = WaitingStatus(not_running)
 
+    def _on_upgrade_charm(self, _) -> None:
+        """Re-render the auth file, which is lost in a pod reschedule."""
+        self.render_auth_file_if_available()
+
     def reload_pgbouncer(self) -> None:
         """Reloads pgbouncer application.
 

tests/integration/relations/pgbouncer_provider/helpers.py

@@ -130,6 +130,7 @@ async def build_connection_string(
     *,
     relation_id: str = None,
     read_only_endpoint: bool = False,
+    database: str = None,
 ) -> str:
     """Build a PostgreSQL connection string.
 
@@ -140,12 +141,14 @@ async def build_connection_string(
         relation_id: id of the relation to get connection data from
         read_only_endpoint: whether to choose the read-only endpoint
             instead of the read/write endpoint
+        database: optional database to be used in the connection string
 
     Returns:
         a PostgreSQL connection string
     """
     # Get the connection data exposed to the application through the relation.
-    database = f'{application_name.replace("-", "_")}_{relation_name.replace("-", "_")}'
+    if database is None:
+        database = f'{application_name.replace("-", "_")}_{relation_name.replace("-", "_")}'
     username = await get_application_relation_data(
         ops_test, application_name, relation_name, "username", relation_id
     )
@@ -197,3 +200,10 @@ async def check_new_relation(
     assert (
         test_data in json.loads(run_query["results"])[0]
     ), f"smoke check failed. Query output: {run_query}"
+
+
+async def delete_pod(ops_test: OpsTest, unit_name: str) -> None:
+    """Delete a pod."""
+    model = ops_test.model.info
+    client = AsyncClient(namespace=model.name)
+    await client.delete(Pod, name=unit_name.replace("/", "-"))

tests/integration/relations/pgbouncer_provider/test_pgbouncer_provider.py

@@ -6,6 +6,7 @@
 import logging
 from pathlib import Path
 
+import psycopg2
 import pytest
 import yaml
 from pytest_operator.plugin import OpsTest
@@ -29,6 +30,7 @@
 from .helpers import (
     build_connection_string,
     check_new_relation,
+    delete_pod,
     get_application_relation_data,
     run_sql_on_application_charm,
 )
@@ -442,3 +444,25 @@ async def test_relation_with_data_integrator(ops_test: OpsTest):
     await ops_test.model.add_relation(f"{PGB}:database", DATA_INTEGRATOR_APP_NAME)
     async with ops_test.fast_forward():
         await ops_test.model.wait_for_idle(status="active")
+
+
+async def test_connection_is_possible_after_pod_deletion(ops_test: OpsTest) -> None:
+    """Tests that the connection is possible after the pod is deleted."""
+    # Delete the pod.
+    unit = ops_test.model.applications[PGB].units[0]
+    await delete_pod(ops_test, unit.name)
+    await ops_test.model.wait_for_idle(status="active", idle_period=3)
+
+    # Test the connection.
+    connection_string = await build_connection_string(
+        ops_test, DATA_INTEGRATOR_APP_NAME, relation_name="postgresql", database="test-database"
+    )
+    connection_string += " port=6432"
+    connection = None
+    try:
+        connection = psycopg2.connect(connection_string)
+    except psycopg2.Error:
+        assert False, "failed to connect to PgBouncer after deleting it's pod"
+    finally:
+        if connection is not None:
+            connection.close()