Connecting to Unix domain socket fails

[margdoc]

When trying to connect to unix domain socket, python driver throws following error:

Traceback (most recent call last):
  File "/home/margdoc/Workspace/scylla/maintenance_mode_testing.py", line 5, in <module>
    s = c.connect()
        ^^^^^^^^^^^
  File "cassandra/cluster.py", line 1750, in cassandra.cluster.Cluster.connect
  File "cassandra/cluster.py", line 1776, in cassandra.cluster.Cluster.connect
  File "cassandra/cluster.py", line 1763, in cassandra.cluster.Cluster.connect
  File "cassandra/cluster.py", line 3581, in cassandra.cluster.ControlConnection.connect
  File "cassandra/cluster.py", line 3642, in cassandra.cluster.ControlConnection._reconnect_internal
cassandra.cluster.NoHostAvailable: ('Unable to connect to any servers', {'test_socket': IndexError('string index out of range')})

In function:

python-driver/cassandra/connection.py

Lines 926 to 961 in 679ad24

	def _connect_socket(self):
	sockerr = None
	addresses = self._get_socket_addresses()
	port = None
	for (af, socktype, proto, _, sockaddr) in addresses:
	try:
	self._socket = self._socket_impl.socket(af, socktype, proto)
	if self.ssl_context:
	self._wrap_socket_from_context()
	elif self.ssl_options:
	if not self._ssl_impl:
	raise RuntimeError("This version of Python was not compiled with SSL support")
	self._socket = self._ssl_impl.wrap_socket(self._socket, **self.ssl_options)
	self._socket.settimeout(self.connect_timeout)
	self._initiate_connection(sockaddr)
	self._socket.settimeout(None)
	local_addr = self._socket.getsockname()
	log.debug('Connection %s %s:%s -> %s:%s', id(self), local_addr[0], local_addr[1], sockaddr[0], sockaddr[1])
	if self._check_hostname:
	self._match_hostname()
	sockerr = None
	break
	except socket.error as err:
	if self._socket:
	self._socket.close()
	self._socket = None
	sockerr = err
	if sockerr:
	raise socket.error(sockerr.errno, "Tried connecting to %s. Last error: %s" %
	([a[4] for a in addresses], sockerr.strerror or sockerr))
	if self.sockopts:
	for args in self.sockopts:
	self._socket.setsockopt(*args)

Line:

log.debug('Connection %s %s:%s -> %s:%s', id(self), local_addr[0], local_addr[1], sockaddr[0], sockaddr[1])

Reproducer:

Socket created in a terminal:

nc -lkU test_socket 

Code that uses python driver:

from cassandra.cluster import Cluster
from cassandra.connection import UnixSocketEndPoint

c = Cluster([UnixSocketEndPoint("test_socket")])
s = c.connect()

[kbr-scylla]

Some more context

• prevents us from using or testing maintenance port: Add maintenance socket scylladb#16172
• this is a regression, introduced in Jan 2022: f4f3186

cc @Lorak-mmk @avelanarius

[avelanarius]

I will work on fixing this problem. We discussed with @Lorak-mmk that after that fix is merged, we will release the next version of Python Driver (not waiting for any more changes like merging upstream or any inflight PRs).