wait_poll

# File activerecord/lib/active_record/connection_adapters/abstract/connection_pool.rb, line 194
          def wait_poll(timeout)
            @num_waiting += 1

            t0 = Concurrent.monotonic_time
            elapsed = 0
            loop do
              ActiveSupport::Dependencies.interlock.permit_concurrent_loads do
                @cond.wait(timeout - elapsed)
              end

              return remove if any?

              elapsed = Concurrent.monotonic_time - t0
              if elapsed >= timeout
                msg = "could not obtain a connection from the pool within %0.3f seconds (waited %0.3f seconds); all pooled connections were in use" %
                  [timeout, elapsed]
                raise ConnectionTimeoutError, msg
              end
            end
          ensure
            @num_waiting -= 1
          end