thread.rb

module ActiveRecord
  class Connection
    def connect
      Thread.current.thread_variable_set(:connection_id, 123)
    end
  end
end

module Sequel
  class Connection
    def connect
      Thread.current.thread_variable_set(:connection_id, 234)
    end
  end
end

# Both ActiveRecord and Sequel access the same connection_id thread local variable.