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.

2 files changed, 2 insertions, 2 deletions

diff --git a/Lib/multiprocessing/managers.py b/Lib/multiprocessing/managers.py
index 96cebc6..76b915d 100644
--- a/Lib/multiprocessing/managers.py
+++ b/Lib/multiprocessing/managers.py
@@ -156,7 +156,7 @@ class Server(object):
         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 6607650..b8afb0f 100644
--- a/Lib/multiprocessing/resource_sharer.py
+++ b/Lib/multiprocessing/resource_sharer.py
@@ -123,7 +123,7 @@ class _ResourceSharer(object):
         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