Add: auto connect to mqtt broker as soon as one is available (#727)

In case ospd-openvas was started without a broker running, the connection fails and ospd-openvas prints that notus is unavailable. This patch solves this issue by trying to connect to the broker every 10 seconds in case the last try failed.

ospd_openvas/daemon.py

@@ -27,7 +27,6 @@
 
 from typing import Callable, Optional, Dict, List, Tuple, Iterator, Any
 from datetime import datetime
-from socket import gaierror
 
 from pathlib import Path
 from os import geteuid, environ
@@ -527,24 +526,14 @@ def init(self, server: BaseServer) -> None:
         notus_handler = NotusResultHandler(self.report_results)
 
         if self._mqtt_broker_address:
-            try:
-                client = MQTTClient(
-                    self._mqtt_broker_address, self._mqtt_broker_port, "ospd"
-                )
-                daemon = MQTTDaemon(client)
-                subscriber = MQTTSubscriber(client)
+            client = MQTTClient(
+                self._mqtt_broker_address, self._mqtt_broker_port, "ospd"
+            )
+            daemon = MQTTDaemon(client)
+            subscriber = MQTTSubscriber(client)
 
-                subscriber.subscribe(
-                    ResultMessage, notus_handler.result_handler
-                )
-                daemon.run()
-            except (ConnectionRefusedError, gaierror, ValueError) as e:
-                logger.error(
-                    "Could not connect to MQTT broker at %s, error was: %s."
-                    " Unable to get results from Notus.",
-                    self._mqtt_broker_address,
-                    e,
-                )
+            subscriber.subscribe(ResultMessage, notus_handler.result_handler)
+            daemon.run()
         else:
             logger.info(
                 "MQTT Broker Adress empty. MQTT disabled. Unable to get Notus"

ospd_openvas/messaging/mqtt.py

@@ -19,6 +19,9 @@
 import logging
 
 from functools import partial
+from socket import gaierror, timeout
+from threading import Thread
+from time import sleep
 from typing import Callable, Type
 
 import paho.mqtt.client as mqtt
@@ -156,9 +159,32 @@ def __init__(
         self,
         client: MQTTClient,
     ):
-        self._client = client
-
-        self._client.connect()
+        self._client: MQTTClient = client
+
+    def _try_connect_loop(self):
+        while True:
+            try:
+                self._client.connect()
+                self._client.loop_start()
+                logger.info("Successfully connected to MQTT broker")
+                return
+            except (gaierror, ValueError) as e:
+                logger.error(
+                    "Could not connect to MQTT broker, error was: %s."
+                    " Unable to get results from Notus.",
+                    e,
+                )
+                return
+            # ConnectionRefusedError - when mqtt declines connection
+            # timeout - when address is not reachable
+            # OSError - in container when address cannot be assigned
+            except (ConnectionRefusedError, timeout, OSError) as e:
+                logger.warning(
+                    "Could not connect to MQTT broker, error was: %s."
+                    " Trying again in 10s.",
+                    e,
+                )
+                sleep(10)
 
     def run(self):
-        self._client.loop_start()
+        Thread(target=self._try_connect_loop, daemon=True).start()

tests/messaging/test_mqtt.py

@@ -98,13 +98,13 @@ def test_connect(self):
         # pylint: disable=unused-variable
         daemon = MQTTDaemon(client)
 
-        client.connect.assert_called_with()
-
     def test_run(self):
         client = mock.MagicMock()
 
         daemon = MQTTDaemon(client)
 
         daemon.run()
 
+        client.connect.assert_called_with()
+
         client.loop_start.assert_called_with()