ruby-thread issue? https://github.com/meh/ruby-thread/issues/5

chart_export.rb

require 'thread/pool'

class ChartExport
  def self._threads_test
    a = Queue.new
    1000.times {
      pool = Thread.pool(10)
      100.times {
        pool.process { a << 1 }
      }
      pool.shutdown
    }

    puts "Should be 100000"
    puts a.size
    raise "Invalid result" unless a.size == 100000
  end
end

t.rb

require 'thread/pool'

a = Queue.new
1000.times {
  pool = Thread.pool(10)
  100.times {
    pool.process { a << 1 }
  }
  pool.shutdown
}

puts "Should be 100000"
puts a.size
raise "Invalid result" unless a.size == 100000

Run as:

> repeat 100 (ruby t.rb)
> repeat 5 (rails runner 'ChartExport._threads_test')