Connection Pool returning an instance of Redis and not ConnectionPool - ruby

Question

I am trying to make my Rails app use Resque for managing workers. But, I would like to continue using the ConnectionPool gem.
I have this in an initializer:
puts ENV["REDISTOGO_URL"]
uri = (not ENV["REDISTOGO_URL"].nil?) ? URI.parse(ENV["REDISTOGO_URL"]) : nil
# at this point, debugger confirms $redis is nil
$redis = ConnectionPool::Wrapper.new(:size => 5, :timeout => 3) {
if uri.nil?
Redis.connect
else
Redis.connect(:host => uri.host, :port => uri.port, :password => uri.password)
end
}
$redis # just put this in here for the debugger
# At this point, $redis is #<Redis:0x007fb1b0036bf0>
# when it should be an instance of ConnectionPool::Wrapper
Does anyone have an idea why $redis would not be returned as an instance ConnectionPool::Wrapper?
I've searched in all the gems source code, nowhere does it set the value of $redis. In ConnectionPool's source code, I did not find anything where it would return an instance of Redis instead of itself.
This only happens when I switched from DelayedJob to Resque. So, it would seem that is the problem. However, I'm at a loss.
I am using Unicorn. Here's that file in config.
worker_processes 2
timeout 30
preload_app true
before_fork do |server, worker|
# Replace with MongoDB or whatever
if defined?(ActiveRecord::Base)
ActiveRecord::Base.connection.disconnect!
Rails.logger.info('Disconnected from ActiveRecord')
end
# If you are using Redis but not Resque, change this
if defined?(Resque)
Resque.redis.quit
Rails.logger.info('Disconnected from Redis')
end
sleep 1
end
after_fork do |server, worker|
# Replace with MongoDB or whatever
if defined?(ActiveRecord::Base)
ActiveRecord::Base.establish_connection
Rails.logger.info('Connected to ActiveRecord')
end
# If you are using Redis but not Resque, change this
if defined?(Resque)
# Yes, commented the Resque out for debugging, still get the same problem.
#Resque.redis = ENV['REDISTOGO_URL']
Rails.logger.info('Connected to Redis')
end
end
And finally, the Procfile:
web: bundle exec unicorn -p $PORT -c ./config/unicorn.rb
worker: env TERM_CHILD=1 QUEUE=* bundle exec rake resque:work
I'm using foreman in my develop environment.
Any help is greatly appreciated.

Answer 1

From the docs:
You can use ConnectionPool::Wrapper to wrap a single global connection.
I looks like the ConnectionPool::Wrapper is meant to wrap a single connection to Redis as a convenience for migrating large applications from using Redis directly to using ConnectionPools
If you call $redis.with, you get the #with defined by ConnectionPool
To get an actual connection pool, just change your
ConnectionPool::Wrapper.new(:size => 5, :timeout => 3) { #redis logic }
to
ConnectionPool.new(:size => 5, :timeout => 3) { #redis logic }

Answer 2

Internally ConnectionPool::Wrapper creates a normal ConnectionPool object, and uses method_missing to automatically checkout/checkin from that pool whenever any method is called on the wrapper.
This use of method_missing includes calls to inspect, or class, or any number of methods which are normally used to try to look at the object or figure out its type.
require 'connection_pool'
class MyClass
def foo
'bar'
end
end
obj = MyClass.new
obj.respond_to?(:foo) # true
obj.respond_to?(:with) # false
wrapper = ConnectionPool::Wrapper.new { MyClass.new }
wrapper.respond_to?(:foo) # true
wrapper.respond_to?(:with) # also true! 'with' is a method on ConnectionPool::Wrapper
You do have an instance of ConnectionPool::Wrapper, it just is a bit hard to tell.