From c7d59bd8cfa053e77ae3446c82afff1fd38a4886 Mon Sep 17 00:00:00 2001
From: Ronald Oussoren <ronaldoussoren@mac.com>
Date: Sat, 13 Jan 2024 10:48:33 +0100
Subject: [PATCH] gh-101225: Increase the socket backlog when creating a
 multiprocessing.connection.Listener (#113567)

Increase the backlog for multiprocessing.connection.Listener` objects created
 by `multiprocessing.manager` and `multiprocessing.resource_sharer` to
 significantly reduce the risk of getting a connection refused error when creating
 a `multiprocessing.connection.Connection` to them.
---
 Lib/multiprocessing/managers.py                               | 2 +-
 Lib/multiprocessing/resource_sharer.py                        | 2 +-
 .../Library/2023-12-29-17-46-06.gh-issue-101225.QaEyxF.rst    | 4 ++++
 3 files changed, 6 insertions(+), 2 deletions(-)
 create mode 100644 Misc/NEWS.d/next/Library/2023-12-29-17-46-06.gh-issue-101225.QaEyxF.rst

diff --git a/Lib/multiprocessing/managers.py b/Lib/multiprocessing/managers.py
index 96cebc6eabec89..76b915de74d94e 100644
--- a/Lib/multiprocessing/managers.py
+++ b/Lib/multiprocessing/managers.py
@@ -156,7 +156,7 @@ def __init__(self, registry, address, authkey, serializer):
         Listener, Client = listener_client[serializer]
 
         # do authentication later
-        self.listener = Listener(address=address, backlog=16)
+        self.listener = Listener(address=address, backlog=128)
         self.address = self.listener.address
 
         self.id_to_obj = {'0': (None, ())}
diff --git a/Lib/multiprocessing/resource_sharer.py b/Lib/multiprocessing/resource_sharer.py
index 66076509a1202e..b8afb0fbed3a3c 100644
--- a/Lib/multiprocessing/resource_sharer.py
+++ b/Lib/multiprocessing/resource_sharer.py
@@ -123,7 +123,7 @@ def _start(self):
         from .connection import Listener
         assert self._listener is None, "Already have Listener"
         util.debug('starting listener and thread for sending handles')
-        self._listener = Listener(authkey=process.current_process().authkey)
+        self._listener = Listener(authkey=process.current_process().authkey, backlog=128)
         self._address = self._listener.address
         t = threading.Thread(target=self._serve)
         t.daemon = True
diff --git a/Misc/NEWS.d/next/Library/2023-12-29-17-46-06.gh-issue-101225.QaEyxF.rst b/Misc/NEWS.d/next/Library/2023-12-29-17-46-06.gh-issue-101225.QaEyxF.rst
new file mode 100644
index 00000000000000..ab3c3a5ef23f45
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2023-12-29-17-46-06.gh-issue-101225.QaEyxF.rst
@@ -0,0 +1,4 @@
+Increase the backlog for :class:`multiprocessing.connection.Listener` objects created
+by :mod:`multiprocessing.manager` and :mod:`multiprocessing.resource_sharer` to
+significantly reduce the risk of getting a connection refused error when creating
+a :class:`multiprocessing.connection.Connection` to them.