Add read-only PostgreSQL notification target action

daemon/registry.py

@@ -96,7 +96,8 @@ class Plugin:
                 f"plugin {self.name} does not support action {action}"
             )
 
-        handler = getattr(self.module, action, None)
+        handler_name = action.replace(".", "_")
+        handler = getattr(self.module, handler_name, None)
 
         if handler is None:
             raise RegistryError(

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,
+    }

tests/test-notify-target.py

@@ -0,0 +1,80 @@
+#!/usr/bin/env python3
+
+import importlib.util
+import sys
+import time
+import types
+from pathlib import Path
+
+fake_psycopg2 = types.ModuleType("psycopg2")
+fake_psycopg2.Error = Exception
+fake_psycopg2.OperationalError = OSError
+
+fake_extras = types.ModuleType("psycopg2.extras")
+fake_extras.RealDictCursor = object
+fake_psycopg2.extras = fake_extras
+
+sys.modules["psycopg2"] = fake_psycopg2
+sys.modules["psycopg2.extras"] = fake_extras
+
+spec = importlib.util.spec_from_file_location(
+    "postgresql_plugin",
+    Path("plugins/postgresql/plugin.py"),
+)
+plugin = importlib.util.module_from_spec(spec)
+spec.loader.exec_module(plugin)
+
+
+def require(condition, message):
+    if not condition:
+        raise SystemExit("FAIL: " + message)
+
+
+print("===== NOTIFY TARGET ACTION =====")
+
+config = {
+    "PACEMAKER_NODE_NAME": "david-macbookpro",
+}
+
+runtime_state = {
+    "postgresql": {
+        "notification": {
+            "operation": "demote",
+            "demote_uname": "david-macbookpro",
+            "promote_uname": "david-prodesk",
+            "received_at": time.time(),
+        },
+    },
+}
+
+result = plugin.notify_target(config, runtime_state, {})
+require(result["ocf_rc"] == 0, "fresh target query failed")
+require(result["target"] is True, "local demote target was not detected")
+print("matching_target         accepted")
+
+config["PACEMAKER_NODE_NAME"] = "david-eve"
+result = plugin.notify_target(config, runtime_state, {})
+require(result["target"] is False, "mismatched target was accepted")
+print("mismatched_target       rejected")
+
+runtime_state["postgresql"]["notification"]["received_at"] = (
+    time.time() - 121
+)
+result = plugin.notify_target(
+    {"PACEMAKER_NODE_NAME": "david-macbookpro"},
+    runtime_state,
+    {},
+)
+require(result["reason"] == "notification_stale", "stale notification accepted")
+print("stale_notification      rejected")
+
+result = plugin.notify_target(
+    {"PACEMAKER_NODE_NAME": "david-macbookpro"},
+    {},
+    {},
+)
+require(result["reason"] == "notification_missing", "missing notification accepted")
+print("missing_notification    rejected")
+
+print()
+print("NOTIFY_TARGET_TEST_PASS=1")