wait_poll

# File activerecord/lib/active_record/connection_adapters/abstract/connection_pool.rb, line 176
        def wait_poll(timeout)
          @num_waiting += 1

          t0 = Time.now
          elapsed = 0
          loop do
            @cond.wait(timeout - elapsed)

            return remove if any?

            elapsed = Time.now - t0
            if elapsed >= timeout
              msg = 'could not obtain a database connection within %0.3f seconds (waited %0.3f seconds)' %
                [timeout, elapsed]
              raise ConnectionTimeoutError, msg
            end
          end
        ensure
          @num_waiting -= 1
        end