Handle NetlinkDumpInterrupted, fix worker metrics going stale after e…

…xceptions

wgkex/worker/mqtt.py

@@ -9,6 +9,7 @@
 from typing import Any, Optional
 
 import paho.mqtt.client as mqtt
+import pyroute2.netlink.exceptions
 
 from wgkex.common import logger
 from wgkex.common.mqtt import (
@@ -20,9 +21,7 @@
 from wgkex.worker.msg_queue import q
 from wgkex.worker.netlink import (
     get_device_data,
-    link_handler,
     get_connected_peers_count,
-    WireGuardClient,
 )
 
 _HOSTNAME = socket.gethostname()
@@ -206,9 +205,15 @@ def publish_metrics_loop(
     topic = TOPIC_CONNECTED_PEERS.format(domain=domain, worker=_HOSTNAME)
 
     while not exit_event.is_set():
-        publish_metrics(client, topic, domain)
-        # This drifts slightly over time, doesn't matter for us
-        exit_event.wait(_METRICS_SEND_INTERVAL)
+        try:
+            publish_metrics(client, topic, domain)
+        except Exception as e:
+            # Don't crash the thread when an exception is encountered
+            logger.error(f"Exception during publish metrics task for {domain}:")
+            logger.error(e)
+        finally:
+            # This drifts slightly over time, doesn't matter for us
+            exit_event.wait(_METRICS_SEND_INTERVAL)
 
     # Set peers metric to -1 to mark worker as offline
     # Use QoS 1 (at least once) to make sure the broker notices
@@ -227,7 +232,15 @@ def publish_metrics(client: mqtt.Client, topic: str, domain: str) -> None:
             f"Could not get interface name for domain {domain}. Skipping metrics publication"
         )
         return
-    peer_count = get_connected_peers_count(iface)
+
+    try:
+        peer_count = get_connected_peers_count(iface)
+    except pyroute2.netlink.exceptions.NetlinkDumpInterrupted:
+        # Handle gracefully, don't update metrics
+        logger.info(
+            "Caught NetlinkDumpInterrupted exception while collecting metrics for domain {domain}"
+        )
+        return
 
     # Publish metrics, retain it at MQTT broker so restarted wgkex broker has metrics right away
     client.publish(topic, peer_count, retain=True)

wgkex/worker/mqtt_test.py

@@ -7,6 +7,7 @@
 
 import mock
 import paho.mqtt.client
+import pyroute2.netlink.exceptions
 
 from wgkex.common.mqtt import TOPIC_CONNECTED_PEERS
 from wgkex.worker import mqtt
@@ -128,6 +129,61 @@ def test_publish_metrics_loop_success(self, conn_peers_mock, config_mock):
 
         self.assertFalse(thread.is_alive())
 
+    @mock.patch.object(mqtt, "_METRICS_SEND_INTERVAL", 0.02)
+    @mock.patch.object(mqtt, "get_config")
+    @mock.patch.object(mqtt, "get_connected_peers_count")
+    def test_publish_metrics_loop_no_exception(self, conn_peers_mock, config_mock):
+        """Tests that an exception doesn't interrupt the loop"""
+        config_mock.return_value = _get_config_mock()
+        conn_peers_mock.side_effect = Exception("Mocked exception")
+        mqtt_client = mock.MagicMock(spec=paho.mqtt.client.Client)
+
+        ee = threading.Event()
+        thread = threading.Thread(
+            target=mqtt.publish_metrics_loop,
+            args=(ee, mqtt_client, "_ffmuc_domain.one"),
+        )
+        thread.start()
+
+        i = 0
+        while i < 20 and not len(conn_peers_mock.mock_calls) >= 2:
+            i += 1
+            sleep(0.1)
+
+        self.assertTrue(
+            len(conn_peers_mock.mock_calls) >= 2,
+            "get_connected_peers_count must be called at least twice",
+        )
+
+        mqtt_client.publish.assert_not_called()
+
+        ee.set()
+
+        i = 0
+        while i < 20 and thread.is_alive():
+            i += 1
+            sleep(0.1)
+
+        self.assertFalse(thread.is_alive())
+
+    @mock.patch.object(mqtt, "get_config")
+    @mock.patch.object(mqtt, "get_connected_peers_count")
+    def test_publish_metrics_NetlinkDumpInterrupted(self, conn_peers_mock, config_mock):
+        config_mock.return_value = _get_config_mock()
+        conn_peers_mock.side_effect = (
+            pyroute2.netlink.exceptions.NetlinkDumpInterrupted()
+        )
+        mqtt_client = mock.MagicMock(spec=paho.mqtt.client.Client)
+
+        domain = mqtt.get_config().domains[0]
+        hostname = socket.gethostname()
+        topic = TOPIC_CONNECTED_PEERS.format(domain=domain, worker=hostname)
+
+        # Must not raise NetlinkDumpInterrupted, but handle gracefully by doing nothing
+        mqtt.publish_metrics(mqtt_client, topic, domain)
+
+        mqtt_client.publish.assert_not_called()
+
     @mock.patch.object(mqtt, "get_config")
     def test_on_message_wireguard_success(self, config_mock):
         # Tests on_message for success.

wgkex/worker/netlink.py

@@ -9,8 +9,7 @@
 from textwrap import wrap
 from typing import Any, Dict, List, Tuple
 
-import pyroute2
-import pyroute2.netlink
+import pyroute2, pyroute2.netlink, pyroute2.netlink.exceptions
 
 from wgkex.common.utils import mac2eui64
 from wgkex.common import logger
@@ -218,12 +217,22 @@ def get_connected_peers_count(wg_interface: str) -> int:
         wg_interface: The WireGuard interface to query.
 
     Returns:
-        # The number of peers which have recently seen a handshake.
+        The number of peers which have recently seen a handshake.
+
+    Raises:
+        NetlinkDumpInterrupted if the interface data has changed while it was being returned by netlink
     """
     three_mins_ago_in_secs = int((datetime.now() - timedelta(minutes=3)).timestamp())
     logger.info("Counting connected wireguard peers for interface %s.", wg_interface)
     with pyroute2.WireGuard() as wg:
-        msgs = wg.info(wg_interface)
+        try:
+            msgs = wg.info(wg_interface)
+        except pyroute2.netlink.exceptions.NetlinkDumpInterrupted:
+            # Normal behaviour, data has changed while it was being returned by netlink.
+            # Retry once, don't catch the exception this time, and let the caller handle it.
+            # See https://github.com/svinota/pyroute2/issues/874
+            msgs = wg.info(wg_interface)
+
         logger.debug("Got infos for connected peers: %s.", msgs)
         count = 0
         for msg in msgs:

wgkex/worker/netlink_test.py

@@ -9,10 +9,11 @@
 # any testing platform can execute tests.
 import sys
 
-sys.modules["pyroute2"] = mock.MagicMock()
-sys.modules["pyroute2.WireGuard"] = mock.MagicMock()
-sys.modules["pyroute2.IPRoute"] = mock.MagicMock()
-sys.modules["pyroute2.NDB"] = mock.MagicMock()
+import pyroute2.netlink.exceptions as pyroute2_netlink_exceptions
+
+pyroute2_module_mock = mock.MagicMock()
+pyroute2_module_mock.netlink.exceptions = pyroute2_netlink_exceptions
+sys.modules["pyroute2"] = pyroute2_module_mock
 sys.modules["pyroute2.netlink"] = mock.MagicMock()
 from pyroute2 import WireGuard
 from pyroute2 import IPRoute
@@ -229,6 +230,26 @@ def msg_get_attr(attr: str):
         ret = netlink.get_connected_peers_count("wg-welt")
         self.assertEqual(ret, 3)
 
+    @mock.patch("pyroute2.WireGuard")
+    def test_get_connected_peers_count_NetlinkDumpInterrupted(self, pyroute2_wg_mock):
+        """Tests getting the correct number of connected peers for an interface."""
+
+        nl_wg_mock_ctx = mock.MagicMock()
+        wg_info_mock = mock.MagicMock(
+            side_effect=(pyroute2_netlink_exceptions.NetlinkDumpInterrupted),
+        )
+        nl_wg_mock_ctx.info = wg_info_mock
+
+        nl_wg_mock_inst = pyroute2_wg_mock.return_value
+        nl_wg_mock_inst.__enter__ = mock.MagicMock(return_value=nl_wg_mock_ctx)
+
+        self.assertRaises(
+            pyroute2_netlink_exceptions.NetlinkDumpInterrupted,
+            netlink.get_connected_peers_count,
+            "wg-welt",
+        )
+        self.assertTrue(len(wg_info_mock.mock_calls) == 2)
+
     def test_get_device_data_success(self):
         def msg_get_attr(attr: str):
             if attr == "WGDEVICE_A_LISTEN_PORT":