Ash FrameworkAF
Ash Framework•3y ago•
12 replies
barnabasj

Recursive Flows

Hi I'm trying to right a flow that runs itself given a condition.

defmodule Demo.Inventory.Flows.Search do
  @moduledoc """

  """

  use Ash.Flow, otp_app: :demo

  flow do
    api(Demo.Support)

    argument(:size, :integer)

    argument(:token, :string)

    argument(:query, :struct)

    argument(:check_in, :date) do
      allow_nil? false
    end

    argument(:check_out, :date) do
      allow_nil? false
    end

    argument(:occupancies, {:array, Demo.Inventory.Resources.Types.Occupancy}) do
      allow_nil? false
    end

    returns(:merge_results)
  end

  steps do
    custom :get_hotels, Demo.Inventory.Flows.Steps.GetHotels do
      input(%{
        check_in: arg(:check_in),
        check_out: arg(:check_out),
        occupancies: arg(:occupancies),
        page: [limit: arg(:size), after: arg(:token)]
      })
    end

    custom :filter_unavailable_hotels, Demo.Inventory.Flows.Steps.FilterUnavailableHotels do
      input %{
        hotels: result(:get_hotels)
      }
    end

    custom :need_more_hotels?, Demo.Inventory.Flows.Steps.NeedMoreHotels do
      input %{
        keyset: result(:get_hotels),
        available_hotels: result(:filter_unavailable_hotels),
        needed_size: arg(:size)
      }
    end

    branch :maybe_get_more_hotels, result(:need_more_hotels?) do
      output :get_next_token

      custom :get_next_token, fn %{hotels: hotels}, _ ->
        {:ok, get_in(Map.from_struct(List.last(hotels)), [:__metadata__, :keyset])}
      end do
        input %{
          hotels: result(:filter_unavailable_hotels)
        }
      end

      custom :get_number_of_missing_hotels, fn %{hotels: hotels, size: size}, _ ->
        {:ok, size - length(hotels)}
      end do
        input %{
          hotels: result(:filter_unavailable_hotels),
          size: arg(:size)
        }
      end

      run_flow :get_more_hotels, __MODULE__ do
        input %{
          check_in: arg(:check_in),
          check_out: arg(:check_out),
          occupancies: arg(:occupancies),
          size: result(:get_number_of_missing_hotels),
          token: result(:get_next_token)
        }
      end
    end

    custom :merge_results, Demo.Inventory.Flows.Steps.MergeResults do
      input %{
        hotels: result(:get_hotels),
        more_hotels: result(:maybe_get_more_hotels)
      }
    end
  end
end


This leads to somekind of infinity recursion. I also tried copying the flow to a different file but that lead to an engine deadlock, it seems like the "sub" flow is run in the same context as the "parent" flow leading and as they both have the same step names it does not know which of the steps belong to which flow.
Was this page helpful?