Add read-only PostgreSQL demotion database probe

tests/test-demote-database.py

@@ -0,0 +1,139 @@
+#!/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)
+
+
+class Cursor:
+    def __enter__(self):
+        return self
+
+    def __exit__(self, *args):
+        return False
+
+    def execute(self, query):
+        pass
+
+    def fetchone(self):
+        return {
+            "in_recovery": True,
+            "replay_paused": False,
+            "receive_lsn": "14/1C07A910",
+            "replay_lsn": "14/1C07A910",
+            "receiver_status": "streaming",
+            "slot_name": "ha_pg_david_eve",
+        }
+
+
+class Connection:
+    autocommit = False
+
+    def cursor(self, cursor_factory=None):
+        return Cursor()
+
+    def close(self):
+        pass
+
+
+plugin.monitor = lambda config, runtime_state: {
+    "ha": {"ocf_rc": plugin.OCF_RUNNING_PROMOTED},
+    "primary": {"current_wal_lsn": "14/1C07A920"},
+}
+
+plugin.read_secret = lambda path: "test-password"
+plugin.psycopg2.connect = lambda **kwargs: Connection()
+
+runtime_state = {
+    "postgresql": {
+        "notification": {
+            "type": "pre",
+            "operation": "demote",
+            "demote_uname": "david-prodesk",
+            "promote_uname": "david-eve",
+            "received_at": time.time(),
+        },
+    },
+}
+
+config = {
+    "PACEMAKER_NODE_NAME": "david-prodesk",
+    "PG_REPLICATION_PEERS": (
+        "david-prodesk=192.168.1.4:5432,"
+        "david-eve=192.168.1.3:5432"
+    ),
+    "PGPASSWORD_FILE": "/run/secrets/postgres_password",
+    "PGUSER": "david",
+    "PGDATABASE": "david",
+}
+
+result = plugin.demote_database(config, runtime_state, {})
+
+assert result["ocf_rc"] == 0
+assert result["ready"] is True
+assert result["mutation"] is False
+assert result["final_handoff_required"] is True
+assert result["successor_node"] == "david-eve"
+assert result["successor_slot_name"] == "ha_pg_david_eve"
+assert result["checks"]["successor_streaming"] is True
+assert result["checks"]["successor_replay_not_paused"] is True
+assert result["wal_lag_bytes"] == 16
+
+print("valid_database_probe     accepted")
+print("wal_lag_reported         accepted")
+print()
+print("DEMOTE_DATABASE_TEST_PASS=1")
+
+
+plugin.monitor = lambda config, runtime_state: {
+    "ha": {"ocf_rc": plugin.OCF_SUCCESS},
+    "primary": None,
+}
+
+result = plugin.demote_database(config, runtime_state, {})
+
+assert result["ocf_rc"] == 1
+assert result["reason"] == "local_not_primary"
+print("local_not_primary        rejected")
+
+
+plugin.monitor = lambda config, runtime_state: {
+    "ha": {"ocf_rc": plugin.OCF_RUNNING_PROMOTED},
+    "primary": {"current_wal_lsn": "14/1C07A920"},
+}
+
+
+def unavailable(**kwargs):
+    raise plugin.psycopg2.OperationalError(
+        "connection refused"
+    )
+
+
+plugin.psycopg2.connect = unavailable
+
+result = plugin.demote_database(config, runtime_state, {})
+
+assert result["ocf_rc"] == 1
+assert result["reason"] == "successor_unreachable"
+print("successor_unreachable    rejected")
+
+print("DEMOTE_DATABASE_FAILURE_TEST_PASS=1")