Graham McIntire
9334539442
Previously retry: :transient only retried connection errors, not HTTP 429 rate limits. All clients now use a custom retry function that handles 429, 500, 502, 503, 504 with 5 retries and jittered backoff.
122 lines
3.5 KiB
Elixir
122 lines
3.5 KiB
Elixir
defmodule Microwaveprop.Terrain.ElevationClient do
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@moduledoc false
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@batch_size 100
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@spec fetch_elevation_profile(float(), float(), float(), float(), pos_integer()) ::
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{:ok, list(map())} | {:error, String.t()}
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def fetch_elevation_profile(lat1, lon1, lat2, lon2, n \\ 64) do
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pts = sample_path(lat1, lon1, lat2, lon2, n)
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dist_km = haversine_km(lat1, lon1, lat2, lon2)
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with {:error, e1} <- fetch_batched(pts, :open_meteo),
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{:error, e2} <- fetch_batched(pts, :open_topo) do
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{:error, "Elevation fetch failed: #{e1} | #{e2}"}
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else
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{:ok, elevs} ->
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profile =
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pts
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|> Enum.zip(elevs)
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|> Enum.map(fn {pt, elev} ->
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%{lat: pt.lat, lon: pt.lon, d: pt.d, elev: elev || 0.0, dist_km: pt.d * dist_km}
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end)
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{:ok, profile}
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end
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end
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def sample_path(lat1, lon1, lat2, lon2, n) do
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for i <- 0..n do
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f = i / n
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%{
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lat: lat1 + f * (lat2 - lat1),
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lon: lon1 + f * (lon2 - lon1),
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d: f
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}
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end
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end
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defp fetch_batched(pts, source) do
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pts
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|> Enum.chunk_every(@batch_size)
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|> Enum.reduce_while({:ok, []}, fn batch, {:ok, acc} ->
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case fetch_batch(source, batch) do
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{:ok, elevs} -> {:cont, {:ok, acc ++ elevs}}
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{:error, _} = err -> {:halt, err}
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end
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end)
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end
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defp fetch_batch(:open_meteo, batch) do
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lats = Enum.map_join(batch, ",", &Float.to_string(Float.round(&1.lat, 6)))
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lons = Enum.map_join(batch, ",", &Float.to_string(Float.round(&1.lon, 6)))
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url = "https://api.open-meteo.com/v1/elevation?latitude=#{lats}&longitude=#{lons}"
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case Req.get(url, req_options()) do
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{:ok, %{status: 200, body: %{"elevation" => elevs}}} when is_list(elevs) ->
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{:ok, elevs}
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{:ok, %{status: status}} ->
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{:error, "Open-Meteo HTTP #{status}"}
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{:error, reason} ->
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{:error, "Open-Meteo error: #{inspect(reason)}"}
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end
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end
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defp fetch_batch(:open_topo, batch) do
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locations =
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Enum.map_join(batch, "|", fn p ->
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"#{Float.round(p.lat, 6)},#{Float.round(p.lon, 6)}"
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end)
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url = "https://api.opentopodata.org/v1/srtm90m?locations=#{URI.encode(locations)}"
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case Req.get(url, req_options()) do
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{:ok, %{status: 200, body: %{"status" => "OK", "results" => results}}} ->
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{:ok, Enum.map(results, fn r -> r["elevation"] || 0.0 end)}
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{:ok, %{status: status}} ->
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{:error, "OpenTopo HTTP #{status}"}
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{:error, reason} ->
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{:error, "OpenTopo error: #{inspect(reason)}"}
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end
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end
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defp haversine_km(lat1, lon1, lat2, lon2) do
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dlat = deg_to_rad(lat2 - lat1)
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dlon = deg_to_rad(lon2 - lon1)
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rlat1 = deg_to_rad(lat1)
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rlat2 = deg_to_rad(lat2)
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a =
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:math.sin(dlat / 2) ** 2 +
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:math.cos(rlat1) * :math.cos(rlat2) * :math.sin(dlon / 2) ** 2
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2 * 6371.0 * :math.asin(:math.sqrt(a))
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end
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defp deg_to_rad(deg), do: deg * :math.pi() / 180
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defp req_options do
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defaults = [retry: &retry?/2, max_retries: 5, retry_delay: &retry_delay/1]
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overrides = Application.get_env(:microwaveprop, :elevation_req_options, [])
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Keyword.merge(defaults, overrides)
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end
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defp retry?(_request, response) do
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case response do
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%Req.Response{status: status} when status in [429, 500, 502, 503, 504] -> true
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%{__exception__: true} -> true
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_ -> false
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end
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end
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defp retry_delay(n) do
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base = Integer.pow(2, n) * 1_000
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jitter = :rand.uniform(1_000)
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base + jitter
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end
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end
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