refactor(DetailedStopGroup): replace async_stream

[thecristen]

Scope

MBTA-DOTCOM-JV

In the continued vein of, we unearth old but recurring Sentry issues from the archive...

Uncaught exit - {:timeout, {Task.Supervised, :stream, [5000]}}
    lib/task/supervised.ex:349: Elixir.Task.Supervised.Task.Supervised.stream_reduce/7
    lib/enum.ex:4570: Elixir.Enum.Enum.flat_map/2
    lib/dotcom_web/controllers/stop_controller.ex:269: Elixir.DotcomWeb.StopController.DotcomWeb.StopController.get_stop_info/0
    lib/dotcom_web/controllers/stop_controller.ex:44: Elixir.DotcomWeb.StopController.DotcomWeb.StopController.show/2
    lib/dotcom_web/controllers/stop_controller.ex:1: Elixir.DotcomWeb.StopController.DotcomWeb.StopController.action/2
    lib/dotcom_web/controllers/stop_controller.ex:1: Elixir.DotcomWeb.StopController.DotcomWeb.StopController.phoenix_controller_pipeline/2
    lib/phoenix/router.ex:416: Elixir.Phoenix.Router.Phoenix.Router.__call__/5
    deps/plug/lib/plug/error_handler.ex:80: Elixir.DotcomWeb.Router.DotcomWeb.Router.call/2

Implementation

This message appears when Task.async_stream doesn't specify an on_timeout action - the default behavior is the task exits!

In this case I think it's better if we don't create possible timeouts: just get everything anyway without async calls, since we'll always want this page (/stops) to list all the stops.

I think the code had likely been structured this way because fetching and processing all the stops can be kinda slow. So this updated code leverages Stream over Enum in a few spots for some hopeful performance improvements. The flame charts are still massive here, but I did see this page go from producing an SVG of 5.2MB to one that's 3.4MB...

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