[3.12] gh-101225: Increase the socket backlog when creating a multiprocessing.connection.Listener (GH-113567) (#114018)

miss-islington · ronaldoussoren · AA-Turner · web-flow · commit 2aea0e967a28 · 2024-01-14T16:29:15.000+01:00
gh-101225: Increase the socket backlog when creating a multiprocessing.connection.Listener (GH-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. (cherry picked from commit c7d59bd) Co-authored-by: Ronald Oussoren <ronaldoussoren@mac.com> Co-authored-by: Adam Turner <9087854+AA-Turner@users.noreply.github.com>
diff --git a/Lib/multiprocessing/managers.py b/Lib/multiprocessing/managers.py
@@ -153,7 +153,7 @@ 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
@@ -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
@@ -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.
