There seem to be several options for establishing Redis connections for use within EventMachine, and I'm having a hard time understanding the core differences between them.
My goal is to implement Redis within Goliath
The way I establish my connection now is through em-synchrony:
require 'em-synchrony'
require 'em-synchrony/em-redis'
config['redis'] = EventMachine::Synchrony::ConnectionPool.new(:size => 20) do
EventMachine::Protocols::Redis.connect(:host => 'localhost', :port => 6379)
end
What is the difference between the above, and using something like em-hiredis?
If I'm using Redis for sets and basic key:value storage, is em-redis the best solution for my scenario?
what em-synchrony does is patch the em-redis gem to allow using it with fibers which effectively allows it to run in goliath.
Here is a project using Goliath + Redis which can guide you on how to make all this works: https://github.com/igrigorik/mneme
Example with em-hiredis, what goliath do is wrap your request in a fiber so a way to test it is:
require 'rubygems'
require 'bundler/setup'
require 'em-hiredis'
require 'em-synchrony'
EM::run do
Fiber.new do
## this is what you can use in goliath
redis = EM::Hiredis.connect
p EM::Synchrony.sync redis.keys('*')
## end of goliath block
end.resume
end
and the Gemfile I used:
source :rubygems
gem 'em-hiredis'
gem 'em-synchrony'
If you run this example you will get the list of defined keys in your redis database printed on screen. Without the EM::Synchrony.sync call you would get a deferrable but here the fiber is suspended until the calls return and you get the result.