Package: rediscluster
a Python interface to a Cluster of Redis key-value stores.Project GoalsThe goal ofrediscluster-py, together withrediscluster-php,
is to have a consistent, compatible client libraries accross programming languages
when sharding among different Redis instances in a transparent, fast, and
fault tolerant way.rediscluster-pyis based on the awesomeredis-pyStrictRedis
Api, thus the original api commands would work without problems within
the context of a cluster of redis serversTravis CICurrently,rediscluster-pyis being tested via travis ci for python
version 2.6, 2.7 and 3.2:Installation$ sudo pip install redisclusteror alternatively (you really should be using pip though):$ sudo easy_install redisclusterFrom source:$ sudo python setup.py installRunning Tests$ git clone https://github.com/salimane/rediscluster-py.git
$ cd rediscluster-py
$ vi tests/config.py
$ ./run_testsGetting Started>>> import rediscluster
>>> cluster = {
...          # node names
...          'nodes' : { # masters
...                      'node_1' : {'host' : '127.0.0.1', 'port' : 63791},
...                      'node_2' : {'host' : '127.0.0.1', 'port' : 63792},
...                    }
...     }
>>> r = rediscluster.StrictRedisCluster(cluster=cluster, db=0)
>>> r.set('foo', 'bar')
True
>>> r.get('foo')
'bar'Cluster ConfigurationThe cluster configuration is a hash that is mostly based on the idea of a node, which is simply a host:port pair
that points to a single redis-server instance. This is to make sure it doesn’t get tied it
to a specific host (or port).
The advantage of this is that it is easy to add or remove nodes from
the system to adjust the capacity while the system is running.Read Slaves & Write Mastersredisclusteruses the master servers stored in the cluster hash passed during instantiation to auto discover
if any slave is attached to them. It then transparently relay read redis commands to slaves and writes commands to masters.There is also support to only use masters even if read redis commands are issued, just specify it at client instantiation like :>>> r = rediscluster.StrictRedisCluster(cluster=cluster, db=0) # read redis commands are routed to slaves
>>>
>>> r = rediscluster.StrictRedisCluster(cluster=cluster, db=0, mastersonly=True) # read redis commands are routed to mastersPartitioning Algorithmredisclusterdoesn’t used a consistent hashing like some other libraries. In order to map every given key to the appropriate Redis node, the algorithm used,
based on crc32 and modulo, is :(abs(binascii.crc32(<key>) & 0xffffffff) % <number of masters>) + 1this is used to ensure some compatibility with other languages, php in particular.
A functiongetnodeforis provided to get the node a particular key will be/has been stored to.>>> r.getnodefor('foo')
{'node_2': {'host': '127.0.0.1', 'port': 63792}}
>>>Hash TagsIn order to specify your own hash key (so that related keys can all land
on a given node),redisclusterallows you to pass a string  in the form “a{b}” where you’d normally pass a scalar.
The first element of the list is the key to use for the hash and the
second is the real key that should be fetched/modify:>>> r.get("bar{foo}")
>>>
>>> r.mset({"bar{foo}": "bar", "foo": "foo"})
>>>
>>> r.mget(["bar{foo}", "foo"])In that case “foo” is the hash key but “bar” is still the name of
the key that is fetched from the redis node that “foo” hashes to.Multiple Keys Redis CommandsIn the context of storing an application data accross many redis servers, commands taking multiple keys
as arguments are harder to use since, if the two keys will hash to two different
instances, the operation can not be performed. Fortunately, rediscluster is a little fault tolerant
in that it still fetches the right result for those multi keys operations as far as the client is concerned.
To do so it processes the related involved redis servers at interface level.>>> r.sadd('foo', *['a1', 'a2', 'a3'])
3
>>> r.sadd('bar', *['b1', 'a2', 'b3'])
3
>>> r.sdiffstore('foobar', 'foo', 'bar')
2
>>> r.smembers('foobar')
set(['a1', 'a3'])
>>> r.getnodefor('foo')
{'node_2': {'host': '127.0.0.1', 'port': 63792}}
>>> r.getnodefor('bar')
{'node_1': {'host': '127.0.0.1', 'port': 63791}}
>>> r.getnodefor('foobar')
{'node_2': {'host': '127.0.0.1', 'port': 63792}}
>>>Redis-Sharding & Redis-CopyIn order to help with moving an application with a single redis server to a cluster of redis servers
that could take advantage ofrediscluster, i wroteredis-shardingandredis-copyInformationCode:git clonegit://github.com/salimane/rediscluster-py.gitHome:http://github.com/salimane/rediscluster-pyBugs:http://github.com/salimane/rediscluster-py/issuesAuthorrediscluster-pyis developed and maintained by Salimane Adjao Moustapha
(me@salimane.com). It can be found here:http://github.com/salimane/rediscluster-py