This illustrates celluloid-redis issue #9: https://github.com/celluloid/celluloid-redis/issues/9 A repo containing the below code and branches with variations that variously provoke the same bug or not can be found here: https://github.com/Felixyz/celluloid-redis-bug

celluloid_redis_bug.rb

require 'thread'

require 'celluloid/io'
require 'celluloid/redis'

KEY = "magic_key"
VALUE = {a: 1, b:2}

class RedisActor
  include Celluloid::IO

  def initialize(queue)
    @queue = queue
    connect_redis
    set_hash
  end

  def connect_redis
    options = {
      :host     => 'localhost',
      :port     => 6379,
      :password => nil
    }
    options[:driver] = :celluloid
    @redis = ::Redis.new(options)
  end

  def set_hash
    @redis.hmset(KEY, *VALUE)
  end

  def get_hash
    @redis.hgetall(KEY)
  end

  def run_one
    @queue << get_hash
  end

  def run_ten
    10.times { run_one }
  end

end

queue = Queue.new
actor = RedisActor.new(queue)

puts "RUN 10 TIMES IN ONE FIBER"
actor.async.run_ten
10.times { puts queue.pop }

puts "RUN 10 TIMES IN 10 SEPARATE FIBERS"
10.times { actor.async.run_one }
10.times { puts queue.pop }

output, jruby-1.7.4

$ ruby ./celluloid_redis_bug.rb 
RUN 10 TIMES IN ONE FIBER
{"a"=>"1", "b"=>"2"}
{"a"=>"1", "b"=>"2"}
{"a"=>"1", "b"=>"2"}
{"a"=>"1", "b"=>"2"}
{"a"=>"1", "b"=>"2"}
{"a"=>"1", "b"=>"2"}
{"a"=>"1", "b"=>"2"}
{"a"=>"1", "b"=>"2"}
{"a"=>"1", "b"=>"2"}
{"a"=>"1", "b"=>"2"}
RUN 10 TIMES IN 10 SEPARATE FIBERS
{"a"=>"1", "b"=>"2"}
{"a"=>"1", "b"=>"2"}
{"a"=>"1", "b"=>"2"}
<the actor waits forever for fibers to resume>

$ redis-cli monitor
OK
1371110619.433504 [0 127.0.0.1:64267] "hmset" "magic_key" "a" "1" "b" "2"
1371110619.437558 [0 127.0.0.1:64267] "hgetall" "magic_key"
1371110619.439829 [0 127.0.0.1:64267] "hgetall" "magic_key"
1371110619.442623 [0 127.0.0.1:64267] "hgetall" "magic_key"
1371110619.444574 [0 127.0.0.1:64267] "hgetall" "magic_key"
1371110619.446475 [0 127.0.0.1:64267] "hgetall" "magic_key"
1371110619.448381 [0 127.0.0.1:64267] "hgetall" "magic_key"
1371110619.450422 [0 127.0.0.1:64267] "hgetall" "magic_key"
1371110619.452266 [0 127.0.0.1:64267] "hgetall" "magic_key"
1371110619.454113 [0 127.0.0.1:64267] "hgetall" "magic_key"
1371110619.456022 [0 127.0.0.1:64267] "hgetall" "magic_key"
<the first round of ten fetches in one fiber finished successfuly>
1371110621.461116 [0 127.0.0.1:64267] "hgetall" "magic_key"
1371110621.464132 [0 127.0.0.1:64267] "hgetall" "magic_key"
1371110621.467759 [0 127.0.0.1:64267] "hgetall" "magic_key"
1371110621.471275 [0 127.0.0.1:64267] "hgetall" "magic_key"

output, MRI 1.9.3-p194

$ ruby ./celluloid_redis_bug.rb 
RUN 10 TIMES IN ONE FIBER
{"a"=>"1", "b"=>"2"}
{"a"=>"1", "b"=>"2"}
{"a"=>"1", "b"=>"2"}
{"a"=>"1", "b"=>"2"}
{"a"=>"1", "b"=>"2"}
{"a"=>"1", "b"=>"2"}
{"a"=>"1", "b"=>"2"}
{"a"=>"1", "b"=>"2"}
{"a"=>"1", "b"=>"2"}
{"a"=>"1", "b"=>"2"}
RUN 10 TIMES IN 10 SEPARATE FIBERS
{"a"=>"1", "b"=>"2"}
{"a"=>"1", "b"=>"2"}
<the actor waits forever for fibers to resume>

$ redis-cli monitor
OK
1371110766.280246 [0 127.0.0.1:64364] "hmset" "magic_key" "a" "1" "b" "2"
1371110766.280754 [0 127.0.0.1:64364] "hgetall" "magic_key"
1371110766.281429 [0 127.0.0.1:64364] "hgetall" "magic_key"
1371110766.281681 [0 127.0.0.1:64364] "hgetall" "magic_key"
1371110766.281901 [0 127.0.0.1:64364] "hgetall" "magic_key"
1371110766.282135 [0 127.0.0.1:64364] "hgetall" "magic_key"
1371110766.282365 [0 127.0.0.1:64364] "hgetall" "magic_key"
1371110766.282618 [0 127.0.0.1:64364] "hgetall" "magic_key"
1371110766.282826 [0 127.0.0.1:64364] "hgetall" "magic_key"
1371110766.283090 [0 127.0.0.1:64364] "hgetall" "magic_key"
1371110766.283297 [0 127.0.0.1:64364] "hgetall" "magic_key"
<the first round of ten fetches in one fiber finished successfuly>
1371110768.284922 [0 127.0.0.1:64364] "hgetall" "magic_key"
1371110768.285266 [0 127.0.0.1:64364] "hgetall" "magic_key"
1371110768.285331 [0 127.0.0.1:64364] "hgetall" "magic_key"
1371110768.285417 [0 127.0.0.1:64364] "hgetall" "magic_key"
1371110768.285501 [0 127.0.0.1:64364] "hgetall" "magic_key"
1371110768.285584 [0 127.0.0.1:64364] "hgetall" "magic_key"
1371110768.285654 [0 127.0.0.1:64364] "hgetall" "magic_key"
1371110768.285730 [0 127.0.0.1:64364] "hgetall" "magic_key"
1371110768.285811 [0 127.0.0.1:64364] "hgetall" "magic_key"
1371110768.285914 [0 127.0.0.1:64364] "hgetall" "magic_key"