Fix: Ask worker to reconnect if master gets a broken RPC message

locust/exception.py

@@ -69,6 +69,10 @@ class RPCReceiveError(Exception):
     When raised from zmqrpc, client connection should be reestablished.
     """
 
+    def __init__(self, *args: object, addr=None) -> None:
+        super().__init__(*args)
+        self.addr = addr
+
 
 class AuthCredentialsError(ValueError):
     """

locust/rpc/zmqrpc.py

@@ -49,7 +49,7 @@ def recv_from_client(self):
         try:
             msg = Message.unserialize(data[1])
         except (UnicodeDecodeError, msgerr.ExtraData) as e:
-            raise RPCReceiveError("ZMQ interrupted or corrupted message") from e
+            raise RPCReceiveError("ZMQ interrupted or corrupted message", addr=addr) from e
         return addr, msg
 
     def close(self, linger=None):

locust/runners.py

@@ -988,9 +988,21 @@ def client_listener(self) -> NoReturn:
             try:
                 client_id, msg = self.server.recv_from_client()
             except RPCReceiveError as e:
-                # TODO: Add proper reconnect if https://github.com/zeromq/pyzmq/issues/1809 fixed
-                logger.error(f"Unrecognized message detected: {e}")
-                continue
+                client_id = e.addr
+
+                if client_id and client_id in self.clients:
+                    logger.error(f"RPCError when receiving from client: {e}. Will reset client {client_id}.")
+                    try:
+                        self.server.send_to_client(Message("reconnect", None, client_id))
+                    except Exception as error:
+                        logger.error(f"Error sending reconnect message to worker: {error}. Will reset RPC server.")
+                        self.connection_broken = True
+                        gevent.sleep(FALLBACK_INTERVAL)
+                        continue
+                else:
+                    message = f"{e}" if not client_id else f"{e} from {client_id}"
+                    logger.error(f"Unrecognized message detected: {message}")
+                    continue
             except RPCSendError as e:
                 logger.error(f"Error sending reconnect message to worker: {e}. Will reset RPC server.")
                 self.connection_broken = True

locust/test/test_runners.py

@@ -47,6 +47,8 @@
 
 NETWORK_BROKEN = "network broken"
 BAD_MESSAGE = "bad message"
+UNRECOGNIZED_HOST_MESSAGE = "unrecognized host message"
+UNRECOGNIZED_MESSAGE = "unrecognized message"
 
 
 def mocked_rpc(raise_on_close=True):
@@ -82,7 +84,11 @@ def recv_from_client(self):
             if msg.data == NETWORK_BROKEN:
                 raise RPCError()
             if msg.data == BAD_MESSAGE:
-                raise RPCReceiveError("Bad message")
+                raise RPCReceiveError(BAD_MESSAGE, addr=msg.node_id)
+            if msg.data == UNRECOGNIZED_HOST_MESSAGE:
+                raise RPCReceiveError(UNRECOGNIZED_HOST_MESSAGE, addr="FAKE")
+            if msg.data == UNRECOGNIZED_MESSAGE:
+                raise RPCReceiveError(UNRECOGNIZED_MESSAGE)
             return msg.node_id, msg
 
         def close(self, linger=None):
@@ -3040,6 +3046,57 @@ def my_task(self):
             master.start(10, 10)
             sleep(0.1)
             server.mocked_send(Message("stats", BAD_MESSAGE, "zeh_fake_client1"))
+            self.assertEqual(4, len(server.outbox))
+
+            # Expected message order in outbox: ack, spawn, reconnect, ack
+            self.assertEqual(
+                "reconnect", server.outbox[2][1].type, "Master didn't send worker reconnect message when expected."
+            )
+
+    def test_worker_sends_unrecognized_message_to_master(self):
+        """
+        Validate master ignores message from worker when it cannot parse adddress info.
+        """
+
+        class TestUser(User):
+            @task
+            def my_task(self):
+                pass
+
+        with mock.patch("locust.rpc.rpc.Server", mocked_rpc()) as server:
+            master = self.get_runner(user_classes=[TestUser])
+            server.mocked_send(Message("client_ready", __version__, "zeh_fake_client1"))
+            self.assertEqual(1, len(master.clients))
+            self.assertTrue(
+                "zeh_fake_client1" in master.clients, "Could not find fake client in master instance's clients dict"
+            )
+
+            master.start(10, 10)
+            sleep(0.1)
+            server.mocked_send(Message("stats", UNRECOGNIZED_MESSAGE, "zeh_fake_client1"))
+            self.assertEqual(2, len(server.outbox))
+
+    def test_unknown_host_sends_message_to_master(self):
+        """
+        Validate master ignores message that is sent from unknown host
+        """
+
+        class TestUser(User):
+            @task
+            def my_task(self):
+                pass
+
+        with mock.patch("locust.rpc.rpc.Server", mocked_rpc()) as server:
+            master = self.get_runner(user_classes=[TestUser])
+            server.mocked_send(Message("client_ready", __version__, "zeh_fake_client1"))
+            self.assertEqual(1, len(master.clients))
+            self.assertTrue(
+                "zeh_fake_client1" in master.clients, "Could not find fake client in master instance's clients dict"
+            )
+
+            master.start(10, 10)
+            sleep(0.1)
+            server.mocked_send(Message("stats", UNRECOGNIZED_HOST_MESSAGE, "unknown_host"))
             self.assertEqual(2, len(server.outbox))