A key-value store and more

The 2.0.0 release of Redis is out and offers a super-fast key value store that stores data in-memory. It offers a persistent data store along with support for sets, string values and hashes. Performance wise it is extremely fast and offers replication without too much fuss. As a developer it is a joy to use. On OSX you can install it using homebrew:

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brew install redis

and then start the server with

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redis-server

Now you can connect to it with a client and start adding and retrieving data with a client

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redis-cli

Basics

Here’s a basic example of setting and getting a value

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redis> set favorite_drink gin
OK
redis> get favorite_drink
"gin"

Once you have a value you can get information from Redis as to its type:

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redis> type favorite_drink
string

And whether a key exists

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redis> exists favorite_drink
(integer) 1

I’ll cover more of the excellent features in subsequent posts.

Using Ruby and Redis

Redis has wrappers for most lanugages including Ruby, Python and PHP. For Ruby you can install the wrapper with

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sudo gem install redis

You can then use it in scripts with

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require 'rubygems'
require 'redis'

redis = Redis.new
redis.set "foo", "bar"

Great for caches and counters

Redis is great for things like counters. Say for example you want to track the number of times a page has been viewed. This is simple with Redis:

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redis.incr "views"
=> 1
redis.incr "views"
=> 2

For non-persistent data like caching it is a really good solution too. You can even use it as the cache in Rack applications.

Further reading

• Simon Willison’s Redis Tutorial
• Redis: Data Cheeseburgers
• A collection of Redis use cases
• Salvatore Sanfilippo’s blog (the brains behind Redis)
• Redis command reference