Add instrumentation logging

Author: ants

patroni/dcs/__init__.py

@@ -1055,11 +1055,17 @@ def get_replication_slots(self, postgresql: 'Postgresql', member: Tags, *,
 
         slots: Dict[str, Dict[str, Any]] = self._get_members_slots(name, role,
                                                                    member.nofailover, postgresql.can_advance_slots)
+        logger.info('Member slots: %s', slots)
+
         permanent_slots: Dict[str, Any] = self._get_permanent_slots(postgresql, member, role)
 
+        logger.info('Permanent slots: %s', permanent_slots)
+
         disabled_permanent_logical_slots: List[str] = self._merge_permanent_slots(
             slots, permanent_slots, name, role, postgresql.can_advance_slots)
 
+        logger.info('After merging: %s', slots)
+
         if disabled_permanent_logical_slots and show_error:
             logger.error("Permanent logical replication slots supported by Patroni only starting from PostgreSQL 11. "
                          "Following slots will not be created: %s.", disabled_permanent_logical_slots)

patroni/postgresql/slots.py

@@ -572,6 +572,8 @@ def sync_replication_slots(self, cluster: Cluster, tags: Tags) -> List[str]:
 
                 slots = cluster.get_replication_slots(self._postgresql, tags, show_error=True)
 
+                logger.info('sync_replication_slots(): Slots fetched from DCS: %s', slots)
+
                 self._drop_incorrect_slots(cluster, slots)
 
                 # We don't want to clean physical replication slots with xmin feedback if: