Question

I am using Redis to store two databases : 0 and 1 via the Redis-py client library. I would like to create two connections for each database. Currently, I am doing this :

>>> connection0 = redis.Connection(host = 'localhost', port = 6379, db = 0)
>>> connection1 = redis.Connection(host = 'localhost', port = 6379, db = 1)
>>> connection0.connect()

However, I don’t seem to find a way to create a Redis object from the connection.

>>> store0 = redis.Redis(connection0)
>>> store0.info()
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/Library/Frameworks/Python.framework/Versions/7.0/lib/python2.7/site-packages/redis-2.4.11-py2.7.egg/redis/client.py", line 341, in info
    return self.execute_command('INFO')
  File "/Library/Frameworks/Python.framework/Versions/7.0/lib/python2.7/site-packages/redis-2.4.11-py2.7.egg/redis/client.py", line 278, in execute_command
    connection.send_command(*args)
  File "/Library/Frameworks/Python.framework/Versions/7.0/lib/python2.7/site-packages/redis-2.4.11-py2.7.egg/redis/connection.py", line 258, in send_command
    self.send_packed_command(self.pack_command(*args))
  File "/Library/Frameworks/Python.framework/Versions/7.0/lib/python2.7/site-packages/redis-2.4.11-py2.7.egg/redis/connection.py", line 241, in send_packed_command
    self.connect()
  File "/Library/Frameworks/Python.framework/Versions/7.0/lib/python2.7/site-packages/redis-2.4.11-py2.7.egg/redis/connection.py", line 187, in connect
    sock = self._connect()
  File "/Library/Frameworks/Python.framework/Versions/7.0/lib/python2.7/site-packages/redis-2.4.11-py2.7.egg/redis/connection.py", line 198, in _connect
    sock.connect((self.host, self.port))
  File "/Library/Frameworks/Python.framework/Versions/7.0/lib/python2.7/socket.py", line 224, in meth
    return getattr(self._sock,name)(*args)
TypeError: coercing to Unicode: need string or buffer, Connection found

Am I making a rookie mistake here?

Answer 1

You really shouldn’t create connections like that. Let me quote the redis-py documentation.

Behind the scenes, redis-py uses a connection pool to manage
connections to a Redis server. By default, each Redis instance you
create will in turn create its own connection pool. You can override
this behavior and use an existing connection pool by passing an
already created connection pool instance to the connection_pool
argument of the Redis class. You may choose to do this in order to
implement client side sharding or have finer grain control of how
connections are managed.

>>> pool = redis.ConnectionPool(host='localhost', port=6379, db=0)
>>> r = redis.StrictRedis(connection_pool=pool)

You cannot specify a single connection to be used with the library. Each Redis instance will have its own connection pool. When execute_command() is called, it will pop a connection from a the pool(or open a new one) and use that connection. If you only want your client to have max one connection at a time, set max_connections to 1.