From b9e31d79fd08ef3caea4d339a5e0df5db42cc0f5 Mon Sep 17 00:00:00 2001
From: "J.A. de Jong - Redu-Sone B.V., ASCEE V.O.F" <j.a.dejong@ascee.nl>
Date: Tue, 4 May 2021 10:29:51 +0200
Subject: [PATCH] Added Monkeypatch to make multiprocessing work with a list of
 queues in the manager

---
 lasp/lasp_multiprocessingpatch.py | 57 +++++++++++++++++++++++++++++++
 1 file changed, 57 insertions(+)
 create mode 100644 lasp/lasp_multiprocessingpatch.py

diff --git a/lasp/lasp_multiprocessingpatch.py b/lasp/lasp_multiprocessingpatch.py
new file mode 100644
index 0000000..fcd8e79
--- /dev/null
+++ b/lasp/lasp_multiprocessingpatch.py
@@ -0,0 +1,57 @@
+# -*- coding: utf-8 -*-
+"""
+Author: J.A. de Jong
+
+Description: MonkeyPatch required to let the Multiprocessing library work properly.
+Should be applied prior to running any other multiprocessing code. Comes from
+Stackoverflow and is mainly used for managing a list of queues that can be
+shared between processes.
+
+For more information, see:
+https://stackoverflow.com/questions/46779860/multiprocessing-managers-and-custom-classes
+"""
+from multiprocessing import managers
+import logging
+from functools import wraps
+from inspect import signature
+
+orig_AutoProxy = managers.AutoProxy
+
+__all__ = ['apply_patch']
+
+
+@wraps(managers.AutoProxy)
+def AutoProxy(*args, incref=True, manager_owned=False, **kwargs):
+    # Create the autoproxy without the manager_owned flag, then
+    # update the flag on the generated instance. If the manager_owned flag
+    # is set, `incref` is disabled, so set it to False here for the same
+    # result.
+    autoproxy_incref = False if manager_owned else incref
+    proxy = orig_AutoProxy(*args, incref=autoproxy_incref, **kwargs)
+    proxy._owned_by_manager = manager_owned
+    return proxy
+
+
+def apply_patch():
+    if "manager_owned" in signature(managers.AutoProxy).parameters:
+        return
+
+    logging.debug("Patching multiprocessing.managers.AutoProxy to add manager_owned")
+    managers.AutoProxy = AutoProxy
+
+    # re-register any types already registered to SyncManager without a custom
+    # proxy type, as otherwise these would all be using the old unpatched AutoProxy
+    SyncManager = managers.SyncManager
+    registry = managers.SyncManager._registry
+    for typeid, (callable, exposed, method_to_typeid, proxytype) in registry.items():
+        if proxytype is not orig_AutoProxy:
+            continue
+        create_method = hasattr(managers.SyncManager, typeid)
+        SyncManager.register(
+            typeid,
+            callable=callable,
+            exposed=exposed,
+            method_to_typeid=method_to_typeid,
+            create_method=create_method,
+        )
+