rest.rb

require 'sinatra'
require 'redis'
require 'json'

set :redis, Redis.new(:db => 3)

before { content_type :json }

get "/foos" do
  keys = options.redis.keys("foo:*")
  foos = options.redis.multi do
    keys.map {|k| options.redis.hgetall k }
  end
  foos.to_json
end

post "/foos" do
  id = options.redis.incr "foo_counter"
  options.redis.hmset "foo:#{id}", *params[:foo].merge(id: id).to_a.flatten
  {result: "success"}.to_json
end

get "/foos/:id" do
  options.redis.hgetall("foo:#{params[:id]}").to_json
end

post "/foos/:id" do
  record = options.redis.hgetall("foo:#{params[:id]}")
  record.merge! params[:foo]
  options.redis.hmset "foo:#{params[:id]}", *params[:foo].to_a.flatten
  {result: "success"}.to_json
end