Correct and check types on monitoring router and database processes (#…

…3572)

Prior to this PR, the startup code for the monitoring router and database processes had type annotations on queues; but these types were not checked, and were incorrect - they were labelled process-local Queue instead of multiprocessing queues. This did not cause much trouble execution- and mypy-wise, as the interfaces of those two classes are similar enough, but it is confusing to read in a part of the codebase that is already confusing (that confusion is probably what lead to the incorrect annotations in the first place...)

They were not checked because the informal policy of "internal stuff is checked with mypy, external interfaces are checked with typeguard" works badly here:

The startup methods are launched using multiprocessing.Process, and function invocations are not type-checked by mypy across a multiprocessing Process constructor.

Changed Behaviour
This PR introduces typeguard decorators onto the router and database start methods so that this internal checking happens at runtime. This consequently reveals that the type annotations of these methods are incorrect, and so this PR makes those consequential changes.

Further, generic types (Queue[MessageType]) are not supported on multiprocessing.Queues before Python 3.12 - so those generic indices are removed from the type annotations. That is unfortunate and weakens in-process static verification - but they could be re-introduced after Parsl drops Python 3.11 support (around 2027 in the present informal support policy)

parsl/monitoring/db_manager.py

@@ -1,11 +1,14 @@
 import datetime
 import logging
+import multiprocessing.queues as mpq
 import os
 import queue
 import threading
 import time
 from typing import Any, Dict, List, Optional, Set, Tuple, TypeVar, cast
 
+import typeguard
+
 from parsl.dataflow.states import States
 from parsl.errors import OptionalModuleMissing
 from parsl.log_utils import set_file_logger
@@ -305,10 +308,10 @@ def __init__(self,
         self.pending_resource_queue: queue.Queue[MonitoringMessage] = queue.Queue()
 
     def start(self,
-              priority_queue: "queue.Queue[TaggedMonitoringMessage]",
-              node_queue: "queue.Queue[MonitoringMessage]",
-              block_queue: "queue.Queue[MonitoringMessage]",
-              resource_queue: "queue.Queue[MonitoringMessage]") -> None:
+              priority_queue: mpq.Queue,
+              node_queue: mpq.Queue,
+              block_queue: mpq.Queue,
+              resource_queue: mpq.Queue) -> None:
 
         self._kill_event = threading.Event()
         self._priority_queue_pull_thread = threading.Thread(target=self._migrate_logs_to_internal,
@@ -719,11 +722,12 @@ def close(self) -> None:
 
 
 @wrap_with_logs(target="database_manager")
-def dbm_starter(exception_q: "queue.Queue[Tuple[str, str]]",
-                priority_msgs: "queue.Queue[TaggedMonitoringMessage]",
-                node_msgs: "queue.Queue[MonitoringMessage]",
-                block_msgs: "queue.Queue[MonitoringMessage]",
-                resource_msgs: "queue.Queue[MonitoringMessage]",
+@typeguard.typechecked
+def dbm_starter(exception_q: mpq.Queue,
+                priority_msgs: mpq.Queue,
+                node_msgs: mpq.Queue,
+                block_msgs: mpq.Queue,
+                resource_msgs: mpq.Queue,
                 db_url: str,
                 logdir: str,
                 logging_level: int) -> None:

parsl/monitoring/router.py

@@ -1,15 +1,16 @@
 from __future__ import annotations
 
 import logging
+import multiprocessing.queues as mpq
 import os
 import pickle
-import queue
 import socket
 import threading
 import time
 from multiprocessing.synchronize import Event
-from typing import Optional, Tuple, Union
+from typing import Optional, Tuple
 
+import typeguard
 import zmq
 
 from parsl.log_utils import set_file_logger
@@ -33,10 +34,10 @@ def __init__(self,
                  logdir: str = ".",
                  logging_level: int = logging.INFO,
                  atexit_timeout: int = 3,   # in seconds
-                 priority_msgs: "queue.Queue[AddressedMonitoringMessage]",
-                 node_msgs: "queue.Queue[AddressedMonitoringMessage]",
-                 block_msgs: "queue.Queue[AddressedMonitoringMessage]",
-                 resource_msgs: "queue.Queue[AddressedMonitoringMessage]",
+                 priority_msgs: mpq.Queue,
+                 node_msgs: mpq.Queue,
+                 block_msgs: mpq.Queue,
+                 resource_msgs: mpq.Queue,
                  exit_event: Event,
                  ):
         """ Initializes a monitoring configuration class.
@@ -202,12 +203,13 @@ def start_zmq_listener(self) -> None:
 
 
 @wrap_with_logs
-def router_starter(comm_q: "queue.Queue[Union[Tuple[int, int], str]]",
-                   exception_q: "queue.Queue[Tuple[str, str]]",
-                   priority_msgs: "queue.Queue[AddressedMonitoringMessage]",
-                   node_msgs: "queue.Queue[AddressedMonitoringMessage]",
-                   block_msgs: "queue.Queue[AddressedMonitoringMessage]",
-                   resource_msgs: "queue.Queue[AddressedMonitoringMessage]",
+@typeguard.typechecked
+def router_starter(comm_q: mpq.Queue,
+                   exception_q: mpq.Queue,
+                   priority_msgs: mpq.Queue,
+                   node_msgs: mpq.Queue,
+                   block_msgs: mpq.Queue,
+                   resource_msgs: mpq.Queue,
                    exit_event: Event,
 
                    hub_address: str,