using redis and ruby to implement a tiny short url app - ruby

Question

I'm making a short URL app, using Ruby, Sinatra, and Redis. Currently it's under 15 lines:
require 'rubygems'
require 'sinatra'
require 'redis'
require 'uri'
configure do
REDISTOGO_URL = "redis://localhost:6379/"
uri = URI.parse(REDISTOGO_URL)
REDIS = Redis.new(:host => uri.host, :port => uri.port, :password => uri.password)
end
get '/' do
haml :index
end
post '/shorten' do
a = rand(9999)
REDIS.set(a.to_s, params[:long])
"<pre>http://199.19.118.186/get/#{a}</pre>"
#haml :shorten
end
get '/get/:url' do
redirect REDIS.get(params[:url])
end
Where index.haml is a form that POSTs long to /shorten. I've no problem with that.
Right now, however, when I try to use Redis (with the server running, yes), I get this error:
What am I doing wrong?
EDIT: Copy/paste from Emacs... facepalm
EDIT: When trying to access redis alone from ruby (code below), I get this:
/var/lib/gems/1.8/gems/redis-2.2.2/lib/redis/client.rb:47:in `call': ERR unknown command (RuntimeError)
from /var/lib/gems/1.8/gems/redis-2.2.2/lib/redis.rb:841:in `set'
from /usr/lib/ruby/1.8/monitor.rb:242:in `synchronize'
from /var/lib/gems/1.8/gems/redis-2.2.2/lib/redis.rb:840:in `set'
from test_redis.rb:9
With this code:
require 'rubygems'
require 'redis'
require 'uri'
REDISTOGO_URL = "redis://localhost:6379/"
uri = URI.parse(REDISTOGO_URL)
REDIS = Redis.new(:host => uri.host, :port => uri.port, :password => uri.password)
REDIS.set("test", "blah")
puts REDIS.get("test")

Answer 1

Ruby being case sensitive, I would try to replace REDIS.SET by REDIS.set and REDIS.GET by REDIS.get. You can find the documentation of the Redis client here:
https://github.com/ezmobius/redis-rb
I have tested your example with ruby 1.8.7. (default on my Linux box).
After installing sinatra, haml, redis and hiredis gems, I have modified the code as follows:
require 'rubygems'
require 'sinatra'
require 'redis'
require 'uri'
configure do
REDISTOGO_URL = "redis://localhost:6379/"
uri = URI.parse(REDISTOGO_URL)
REDIS = Redis.new(:host => uri.host, :port => uri.port, :password => uri.password)
end
get '/' do
"Hello"
haml :index
end
post '/shorten' do
a = rand(9999)
REDIS.set(a.to_s, "http://"+params[:long])
"<pre>http://localhost:4567/get/#{a}</pre>"
end
get '/get/:url' do
redirect REDIS.get(params[:url])
end
I have added the following template in views/index.haml.
!!!
%html
%head
%title My Sinatra Website
%body
%h1 Welcome
%p
Welcome to my website made with Sinatra and HAML
%form{ :action => "/shorten", :method=>"POST" }
%fieldset
%input{ :type =>"text", :name=>"long" }
%input{ :type =>"submit" }
Once Redis is started on port 6379 and sinatra on port 4567, it works like a charm.
I suggest you check your ruby installation and try to access Redis from ruby with a simple non sinatra script.
UPDATE:
The error message is peculiar because normally, when an unknown command is sent to the server, the faulty command is provided:
ERR unknown command 'dummy'
while you just have:
ERR unknown command
Actually, this specific fix was introduced in Redis server more than 2 years ago (in December 2009) - an eternity for Redis.
https://github.com/antirez/redis/commit/2c14807b2dd5c15f1471bec32a7c6dbb077720ee
In other words, you are trying to use a very old (i.e. pre 1-3) version of Redis server with the last version of the Redis client ruby gem, which probably does not support anymore the initial protocol. You may want to compile and install a recent version of Redis server (it is easy), it should work better.