Uses a JSON dictionary of unit name to bind address, instead of a list.

This allows us to associate units with addresses when dealing with all
bind addresses across peers.

src/charm.py

@@ -3,6 +3,7 @@
 # Licensed under the GPLv3, see LICENSE file for details.
 
 import controlsocket
+import json
 import logging
 import secrets
 import urllib.parse
@@ -33,7 +34,7 @@ def __init__(self, *args):
         self.framework.observe(
             self.on.website_relation_joined, self._on_website_relation_joined)
 
-        self._stored.set_default(db_bind_address='', last_bind_addresses=[], all_bind_addresses=[])
+        self._stored.set_default(db_bind_address='', last_bind_addresses=[], all_bind_addresses=dict())
         self.framework.observe(
             self.on.dbcluster_relation_changed, self._on_dbcluster_relation_changed)
 
@@ -79,7 +80,7 @@ def _on_website_relation_joined(self, event):
         try:
             api_port = self.api_port()
         except AgentConfException as e:
-            logger.error('cannot read controller API port from agent configuration: {}', e)
+            logger.error('cannot read controller API port from agent configuration: %s', e)
             return
 
         address = None
@@ -102,7 +103,7 @@ def _on_metrics_endpoint_relation_created(self, event: RelationJoinedEvent):
         try:
             api_port = self.api_port()
         except AgentConfException as e:
-            logger.error('cannot read controller API port from agent configuration: {}', e)
+            logger.error('cannot read controller API port from agent configuration: %s', e)
             return
 
         metrics_endpoint = MetricsEndpointProvider(
@@ -143,18 +144,17 @@ def _on_dbcluster_relation_changed(self, event):
             # The event only has *other* units so include this
             # unit's bind address if we have managed to set it.
             ip = self._stored.db_bind_address
-            all_bind_addresses = [ip] if ip else []
+            all_bind_addresses = {self.unit.name: ip} if ip else dict()
 
             for unit in event.relation.units:
                 unit_data = event.relation.data[unit]
                 if self.DB_BIND_ADDR_KEY in unit_data:
-                    all_bind_addresses.append(unit_data[self.DB_BIND_ADDR_KEY])
+                    all_bind_addresses[unit.name] = unit_data[self.DB_BIND_ADDR_KEY]
 
-            all_bind_addresses.sort()
             if self._stored.all_bind_addresses == all_bind_addresses:
                 return
 
-            event.relation.data[self.app]['db-bind-addresses'] = ','.join(all_bind_addresses)
+            event.relation.data[self.app]['db-bind-addresses'] = json.dumps(all_bind_addresses)
             self._stored.all_bind_addresses = all_bind_addresses
 
     def _ensure_db_bind_address(self, event):

tests/test_charm.py

@@ -2,6 +2,7 @@
 # Licensed under the GPLv3, see LICENSE file for details.
 
 import ipaddress
+import json
 import os
 import unittest
 from charm import JujuControllerCharm, AgentConfException
@@ -170,7 +171,8 @@ def test_dbcluster_relation_changed_single_addr(self, binding, _):
         self.assertEqual(unit_data['db-bind-address'], '192.168.1.17')
 
         app_data = harness.get_relation_data(relation_id, 'juju-controller')
-        self.assertEqual(app_data['db-bind-addresses'], '192.168.1.100,192.168.1.17')
+        exp = {"juju-controller/0": "192.168.1.17", "juju-controller/1": "192.168.1.100"}
+        self.assertEqual(json.loads(app_data['db-bind-addresses']), exp)
 
         harness.evaluate_status()
         self.assertIsInstance(harness.charm.unit.status, ActiveStatus)