Issue #21455: Add a default backlog to socket.listen().
diff --git a/Modules/socketmodule.c b/Modules/socketmodule.c
index d0149dd..5a2893c 100644
--- a/Modules/socketmodule.c
+++ b/Modules/socketmodule.c
@@ -121,7 +121,7 @@
getsockname() -- return local address\n\
getsockopt(level, optname[, buflen]) -- get socket options\n\
gettimeout() -- return timeout or None\n\
-listen(n) -- start listening for incoming connections\n\
+listen([n]) -- start listening for incoming connections\n\
recv(buflen[, flags]) -- receive data\n\
recv_into(buffer[, nbytes[, flags]]) -- receive data (into a buffer)\n\
recvfrom(buflen[, flags]) -- receive data and sender\'s address\n\
@@ -2534,14 +2534,16 @@
/* s.listen(n) method */
static PyObject *
-sock_listen(PySocketSockObject *s, PyObject *arg)
+sock_listen(PySocketSockObject *s, PyObject *args)
{
- int backlog;
+ /* We try to choose a default backlog high enough to avoid connection drops
+ * for common workloads, yet not too high to limit resource usage. */
+ int backlog = Py_MIN(SOMAXCONN, 128);
int res;
- backlog = _PyLong_AsInt(arg);
- if (backlog == -1 && PyErr_Occurred())
+ if (!PyArg_ParseTuple(args, "|i:listen", &backlog))
return NULL;
+
Py_BEGIN_ALLOW_THREADS
/* To avoid problems on systems that don't allow a negative backlog
* (which doesn't make sense anyway) we force a minimum value of 0. */
@@ -2556,12 +2558,12 @@
}
PyDoc_STRVAR(listen_doc,
-"listen(backlog)\n\
+"listen([backlog])\n\
\n\
-Enable a server to accept connections. The backlog argument must be at\n\
-least 0 (if it is lower, it is set to 0); it specifies the number of\n\
+Enable a server to accept connections. If backlog is specified, it must be\n\
+at least 0 (if it is lower, it is set to 0); it specifies the number of\n\
unaccepted connections that the system will allow before refusing new\n\
-connections.");
+connections. If not specified, a default reasonable value is chosen.");
/*
@@ -3795,7 +3797,7 @@
{"share", (PyCFunction)sock_share, METH_VARARGS,
sock_share_doc},
#endif
- {"listen", (PyCFunction)sock_listen, METH_O,
+ {"listen", (PyCFunction)sock_listen, METH_VARARGS,
listen_doc},
{"recv", (PyCFunction)sock_recv, METH_VARARGS,
recv_doc},