Socket and config flag

config.yaml

@@ -21,6 +21,12 @@ options:
       Virtual IP to use to front pgbouncer units. Used only in case of external node connection.
     type: string
 
+  local_connection_type:
+    default: localhost
+    description: |
+      Type of local connectivity to provide. Must be either 'localhost' or 'socket'. Only applies to the database interface.
+    type: string
+
   pool_mode:
     default: session
     description: |

src/config.py

@@ -19,5 +19,6 @@ class CharmConfig(BaseConfigModel):
     listen_port: PositiveInt
     metrics_port: PositiveInt
     vip: Optional[IPvAnyAddress]
+    local_connection_type: Literal["localhost", "socket"]
     pool_mode: Literal["session", "transaction", "statement"]
     max_db_connections: conint(ge=0)

src/relations/pgbouncer_provider.py

@@ -60,7 +60,7 @@
     RelationDepartedEvent,
 )
 
-from constants import CLIENT_RELATION_NAME
+from constants import CLIENT_RELATION_NAME, PGB_RUN_DIR
 
 logger = logging.getLogger(__name__)
 
@@ -239,8 +239,6 @@ def update_connection_info(self, relation):
         user = f"relation_id_{relation.id}"
         password = self.database_provides.fetch_my_relation_field(relation.id, "password")
 
-        host = "localhost"
-        uri_host = host
         if exposed:
             if self.charm.config.vip:
                 host = str(self.charm.config.vip)
@@ -251,6 +249,13 @@ def update_connection_info(self, relation):
                     self.charm.leader_ip,
                     *[ip for ip in self.charm.peers.units_ips if ip != self.charm.leader_ip],
                 ])
+        elif self.charm.config.local_connection_type == "socket":
+            host = f"{PGB_RUN_DIR}/{self.charm.app.name}/instance_0"
+            uri_host = host
+        else:
+            host = "localhost"
+            uri_host = host
+
         port = self.charm.config.listen_port
 
         initial_status = self.charm.unit.status

tests/integration/relations/pgbouncer_provider/test_pgbouncer_provider.py

@@ -61,6 +61,7 @@ async def test_database_relation_with_charm_libraries(ops_test: OpsTest, pgb_cha
                 pgb_charm_jammy,
                 application_name=PGB,
                 num_units=None,
+                config={"local_connection_type": "socket"},
             ),
             ops_test.model.deploy(
                 PG,

tests/integration/test_config.py

@@ -58,6 +58,7 @@ async def test_config_parameters(ops_test: OpsTest, pgb_charm_jammy) -> None:
         "listen_port": "0",
         "metrics_port": "0",
         "vip": test_string,
+        "local_connection_type": test_string,
         "pool_mode": test_string,
         "max_db_connections": "-1",
     }