Rails 3 uninitialized constant when using thread - multithreading

Question

i am running rails 3 thread to improve the performance of the rake task. sometimes i am getting uninitialized constant when i am trying to access outside class from my current class. as an example when i am trying to access NotificationService class from NotificationApp as shown below then getting error as uninitialized constant NotificationService. This error is not coming every time. sometimes rake task is running fine without the error and sometimes same rake is failing with uninitialized constant. what could be the reason for this and how can i fix this issue?
class NotificationApp < ActiveRecord::Base
def signal_event
NotificationService.notify
end
end
Edit
This is how i am creating threadpool
class ThreadPool
def initialize(size)
#size = size
#jobs = Queue.new
#pool = Array.new(#size) do |i|
Thread.new do
Thread.current[:id] = i
catch(:exit) do
loop do
job, args = #jobs.pop
job.call(*args)
end
end
end
end
end
# add a job to queue
def schedule(*args, &block)
#jobs << [block, args]
end
# run threads and perform jobs from queue
def run!
#size.times do
schedule { throw :exit }
end
#pool.map(&:join)
end
# get all threads created
def threads
#pool
end
def complete!
#pool.each{|t| t.kill}
end
end
and this is how i am using threads
def perform
ReadReplicaHelper.read_from_slave do
pool = ThreadPool.new(CONNECTION_POOL_COUNT - 1)
device_ids.in_groups_of(1000, false) do |devices|
devices.each do |device_id|
device = Device.find_by_id(device_id)
if device
ReadReplicaHelper.read_from_master do
Notification.where(device_id: device_id).each do |notification|
pool.schedule do
pool_method notification, last_status, before_last_status
end
end
end
end
end
end
# Run the Thread Pool
pool.run!
# Kill the threads created in the pool
pool.complete!
end

Answer 1

Make sure your NotificationService class is in a file named app/services/notification_service.rb and that you are loading this services directory.
Also as you are using threads, make sure to join all the threads after calling them