=============================================== Cherrys : a Redis backend for CherryPy sessions

CherryPy_ kicks some serious arse in the 'I am just a HTTP framework' category! As of version 3.2 it supports 4 types of storage for sessions by default:

• Ram
• File
• PostgreSQL_
• Memcached_

Redis is growing in popularity as an alternative to Memcached (and is fully supported on dotCloud_!)

Installation

If you are not using pip yet. Install it and while you are at it consider using virtualenv too.

::

$ pip install cherrys

redis-py and CherryPy are required dependencies hence will be installed if necessary.

We recommend installing hiredis-py_ (a faster parser) as well.

::

$ pip install hiredis

Usage (and abusage)

To tell CherryPy_ which backend to use, we need to specify the storage_type for the sessions tool. You may want to read more about CherryPy configuration.

::

tools.sessions.storage_type : 'redis'

But CherryPy doesn't know Redis. Hence the first thing we need to do is add the cherrys RedisSession class to cherrypy.lib.sessions.

::

import cherrys
cherrypy.lib.sessions.RedisSession = cherrys.RedisSession

It is that simple!

Config dictionary

There are a few optional parameters you can set:

• host [127.0.0.1] (when is_sentinel this is host for sentinel service)
• port [6379] (when is_sentinel this is port for sentinel service)
• ssl [False] (for both sentinel and redis)
• db [0]
• prefix [""] (prepended to session id if given; useful when ACLs are enabled)
• user [None] (for old version of authentication can be set to empty string)
• password [None]
• lock_timeout [None] (None, or time in seconds until session lock expires)
• url [None] (alternative to host/port/ssl/db/user/password combination)

Sentinel-related additional (optional) parameters:

• is_sentinel [False]
• sentinel_pass [None]
• sentinel_service [None]
• tls_skip_verify [False]

A full config dictionary to activate Redis_ backed sessions would look like this.

::

config = {
    'tools.sessions.on' : True,
    'tools.sessions.storage_type' : 'redis',

    'tools.sessions.host': REDIS_HOST,
    'tools.sessions.port': REDIS_PORT,

    'tools.sessions.db': REDIS_DB,
    'tools.sessions.prefix': REDIS_PREFIX,
    'tools.sessions.user': REDIS_USER,
    'tools.sessions.password': REDIS_PASS,
    'tools.sessions.lock_timeout: LOCK_TIME_SECONDS,
}

A full config dictionary to activate RedisSentinelSSL_ backed sessions would look like this.

::

config = {
    'tools.sessions.on' : True,
    'tools.sessions.storage_type' : 'redis',

    'tools.sessions.host': REDIS_HOST,
    'tools.sessions.port': REDIS_PORT,
    'tools.sessions.ssl': True,

    'tools.sessions.db': REDIS_DB,
    'tools.sessions.prefix': REDIS_PREFIX,
    'tools.sessions.user': REDIS_USER,
    'tools.sessions.password': REDIS_PASS,
    'tools.sessions.lock_timeout: LOCK_TIME_SECONDS,

    'tools.sessions.is_sentinel': True,
    'tools.sessions.sentinel_pass': REDIS_SENTINEL_PASS,
    'tools.sessions.sentinel_service': REDIS_SENTINEL_SERVICENAME,
    'tools.sessions.tls_skip_verify': True,
}

Configuration via redis URL

As a shortcut a URL to the redis server can be provided as well.

::

import cherrys
config = {
    'tools.sessions.on' : True,
    # next setting removes the need for initializing `cherrypy.lib.sessions.RedisSession' above:
    'tools.sessions.storage_class' : cherrys.RedisSession,
    'tools.sessions.url': 'redis://your-name:your-pwd@redis-server:6379/2'
}

The number at the end of the URL ("2") denotes the redis database to be used.

Running unittests

Unittests require a running redis-server on localhost:6379 setup without any authentication in place.

Then install pytest into your current virtualenv and start it from your command line:

::

$ pip install pytest
$ pytest

.. _CherryPy: http://www.cherrypy.dev .. _PostgreSQL: http://www.postgresql.org .. _Memcached: http://memcached.org .. _Redis: http://redis.io .. _dotCloud: http://www.dotcloud.com .. _pip: http://pip-installer.org .. _virtualenv: http://www.virtualenv.org .. _redis-py: https://github.com/andymccurdy/redis-py .. _hiredis-py: https://github.com/pietern/hiredis-py .. _configuration: http://docs.cherrypy.org/stable/concepts/config.html .. _RedisSentinelSSL: https://redis.io/topics/sentinel