Add read-only PostgreSQL notification target action

plugins/postgresql/manifest.json

@@ -4,7 +4,8 @@
   "module": "plugin.py",
   "actions": [
     "monitor",
-    "notify"
+    "notify",
+    "notify.target"
   ],
   "required_config": [
     "PGHOST",
@@ -15,6 +16,7 @@
     "PG_REPLICATION_PEERS"
   ],
   "optional_config": [
-    "PG_RECONNECT_GRACE_SECONDS"
+    "PG_RECONNECT_GRACE_SECONDS",
+    "PACEMAKER_NODE_NAME"
   ]
 }

plugins/postgresql/plugin.py

@@ -435,3 +435,82 @@ def notify(config, runtime_state, request_parameters):
         "ocf_rc": OCF_SUCCESS,
         "state": dict(state),
     }
+
+
+NOTIFY_TARGET_MAX_AGE_SECONDS = 120
+
+
+def notify_target(config, runtime_state, request_parameters):
+    """
+    Report whether the local daemon is the target of the last notification.
+
+    This is deliberately read-only. Promotion and demotion execution remain
+    separate actions until target selection is proven in production.
+    """
+    del request_parameters
+
+    node_name = str(
+        config.get("PACEMAKER_NODE_NAME", "")
+    ).strip().lower()
+
+    if not node_name:
+        raise ValueError(
+            "PACEMAKER_NODE_NAME is required for notify.target"
+        )
+
+    notification = _postgres_runtime_state(
+        runtime_state
+    ).get("notification")
+
+    if not isinstance(notification, dict):
+        return {
+            "ocf_rc": 1,
+            "target": False,
+            "reason": "notification_missing",
+            "node": node_name,
+        }
+
+    received_at = notification.get("received_at")
+
+    if not isinstance(received_at, (int, float)):
+        return {
+            "ocf_rc": 1,
+            "target": False,
+            "reason": "notification_timestamp_invalid",
+            "node": node_name,
+        }
+
+    age = time.time() - received_at
+
+    if age < 0 or age > NOTIFY_TARGET_MAX_AGE_SECONDS:
+        return {
+            "ocf_rc": 1,
+            "target": False,
+            "reason": "notification_stale",
+            "age_seconds": age,
+            "node": node_name,
+        }
+
+    operation = notification.get("operation")
+
+    if operation == "demote":
+        target_node = notification.get("demote_uname", "").strip().lower()
+    elif operation == "promote":
+        target_node = notification.get("promote_uname", "").strip().lower()
+    else:
+        return {
+            "ocf_rc": 1,
+            "target": False,
+            "reason": "operation_unsupported",
+            "operation": operation,
+            "node": node_name,
+        }
+
+    return {
+        "ocf_rc": 0,
+        "target": target_node == node_name,
+        "operation": operation,
+        "target_node": target_node,
+        "node": node_name,
+        "age_seconds": age,
+    }