script.rb

CONCURRENCY = 100 # Ensure adequate pool size in database.yml

barrier = Concurrent::CyclicBarrier.new(CONCURRENCY)

jobs = Array.new(CONCURRENCY) do
  lambda do
    ClientNodeDetail.last
  end
end

process = lambda do |i|
  barrier.wait
  begin
    Rails.application.executor.wrap { jobs[i].call }
  ensure
    barrier.wait
  end
end

threads = CONCURRENCY.times.map { |i| Thread.new(i, &process) }

threads.map(&:join)

=begin
NoMethodError: undefined method `default_scope_override' for #<Class:0x152d2a58>
Did you mean?  default_scope_override=
	from org/jruby/RubyBasicObject.java:1653:in `method_missing'
	from /Users/davida/.rvm/gems/jruby-9.1.9.0@backbeat/gems/activerecord-5.0.3/lib/active_record/dynamic_matchers.rb:21:in `method_missing'
	from /Users/davida/.rvm/gems/jruby-9.1.9.0@backbeat/gems/activerecord-5.0.3/lib/active_record/scoping/default.rb:111:in `build_default_scope'
	from /Users/davida/.rvm/gems/jruby-9.1.9.0@backbeat/gems/activerecord-5.0.3/lib/active_record/scoping/named.rb:33:in `default_scoped'
	from /Users/davida/.rvm/gems/jruby-9.1.9.0@backbeat/gems/activerecord-5.0.3/lib/active_record/scoping/named.rb:28:in `all'
	from /Users/davida/.rvm/gems/jruby-9.1.9.0@backbeat/gems/activerecord-5.0.3/lib/active_record/querying.rb:3:in `last'
	from (irb):7:in `block in evaluate'
	from (irb):17:in `block in evaluate'
	from /Users/davida/.rvm/gems/jruby-9.1.9.0@backbeat/gems/activesupport-5.0.3/lib/active_support/execution_wrapper.rb:85:in `wrap'
	from (irb):17:in `block in evaluate'
=end