Using Redis with Ruby

redis_notes.rb

#!/usr/bin/env ruby

require 'redis'
# gem install redis


##
## Connect to DB
##
redis = Redis.new(host: "localhost")

##
## Simple Key/Value Storage
##
redis.set("a", 1)
redis.get("a")

##
## Sorted Set (aka, a key/value with a weight)
##
redis.zadd("popular_fruit", 10, "apple")
redis.zadd("popular_fruit", 20, "banana")
redis.zadd("popular_fruit", 30, "orange")

# start at 0, return everything in descending order
redis.zrevrange("popular_fruit", 0, -1)

# start at 0, return everything in ascending order
redis.zrange("popular_fruit", 0, -1)

# start at 0, return 1 item
redis.zrevrange("popular_fruit", 0, 0)

# start at 0, return 2 items
redis.zrevrange("popular_fruit", 0, 1)


##
## Use colons to namespace the data
##
redis.set("fruit:red",    "apple")
redis.set("fruit:yellow", "banana")


##
## Query ALL keys in database
##
redis.keys()

#
# scan is a cursor based iterator.
# This means that at every call of the command,
# the server returns an updated cursor that the user needs to use as the cursor argument in the next call.
# An iteration starts when the cursor is set to 0, and terminates when the cursor returned by the server is 0. 
#
i = 0
loop do
  results = redis.scan(i)
  i = results.first.to_i
  results.last.each do |key|
    puts "  * " + key.to_s
  end ## each
  break if i == 0
end


##
## Data persistence
##
## Redis only writes data to disk _(dump.rdb)_ when the server is stopped.
## Or under these conditions:
##   * after 15 min, if 1 or more keys changed
##   * after 5 min, if 10 or more keys changed
##   * after 1 min, if 10,000 or more keys changed
##
## To make Redis save to disk every second, set: `appendonly yes`
##



##
## Using Redis as a cache in Rails
##
# config/environments/production.rb
Rails.application.configure do
  config.cache_store = :redis_cache_store, { url: "redis://localhost:6379/0" }
end



Rails.cache.write("a", 1)
Rails.cache.read("a")