Redis Error 8 connecting localhost:6379. nodename nor servname provided, or not known

My environment is Mac OS 10.9.2, python3.3, redis-2.6.9 (64-bit).

I have many threads (nealy 2000) that use the same redis instance to write data, but some threads throw the following exceptions:

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/usr/local/lib/python3.3/site-packages/redis/connection.py", line 250, in connect
    sock = self._connect()
  File "/usr/local/lib/python3.3/site-packages/redis/connection.py", line 268, in _connect
    self.socket_timeout)
  File "/usr/local/Cellar/python3/3.3.4/Frameworks/Python.framework/Versions/3.3/lib/python3.3/socket.py", line 417, in create_connecti
on
    for res in getaddrinfo(host, port, 0, SOCK_STREAM):
socket.gaierror: [Errno 8] nodename nor servname provided, or not known

Traceback (most recent call last):
  File "/usr/local/Cellar/python3/3.3.4/Frameworks/Python.framework/Versions/3.3/lib/python3.3/threading.py", line 901, in _bootstrap_i
nner
    self.run()
  File "/usr/local/Cellar/python3/3.3.4/Frameworks/Python.framework/Versions/3.3/lib/python3.3/threading.py", line 858, in run
    self._target(*self._args, **self._kwargs)
  File "proxypool.py", line 289, in _efficiency_proxy
    self.rdb.zadd(db_proxy, time_delay, proxy)
  File "/usr/local/lib/python3.3/site-packages/redis/client.py", line 1345, in zadd
    return self.execute_command('ZADD', name, *pieces)
  File "/usr/local/lib/python3.3/site-packages/redis/client.py", line 464, in execute_command
    connection.send_command(*args)
  File "/usr/local/lib/python3.3/site-packages/redis/connection.py", line 334, in send_command
    self.send_packed_command(self.pack_command(*args))
  File "/usr/local/lib/python3.3/site-packages/redis/connection.py", line 316, in send_packed_command
    self.connect()
  File "/usr/local/lib/python3.3/site-packages/redis/connection.py", line 253, in connect
    raise ConnectionError(self._error_message(e))
redis.exceptions.ConnectionError: Error 8 connecting localhost:6379. nodename nor servname provided, or not known.

Is there some way to solve this problem?
I tried to connect to redis server when this exception happens and use ulimit -n to set a larger number, but the two methods don't work.

I know why this happened. It's caused by the max number of connections to redis-server and it's related to the max number of file handlers that the OS sets.
If I set:

$ ulimit -n 1024

it works.