Store stub records on empty weather fetches to prevent infinite backfill retries

When ASOS/RAOB/IEMRE APIs return empty data, store a stub record so
dedup checks (has_surface_observations?, has_sounding?, has_iemre_observation?)
see coverage and don't recreate the same jobs on future backfill runs.

lib/microwaveprop/workers/iemre_fetch_worker.ex

@@ -25,7 +25,9 @@ defmodule Microwaveprop.Workers.IemreFetchWorker do
 
       case IemClient.fetch_iemre(lat, lon, date) do
         {:ok, []} ->
-          Logger.info("IEMRE returned empty data for #{lat},#{lon} @ #{date_str}")
+          # Store stub so this lat/lon/date isn't retried on future backfills
+          Weather.upsert_iemre_observation(%{lat: lat, lon: lon, date: date, hourly: []})
+          Logger.info("IEMRE: no data available for #{lat},#{lon} @ #{date_str}, stored stub")
           :ok
 
         {:ok, data} ->

lib/microwaveprop/workers/weather_fetch_worker.ex

@@ -10,6 +10,7 @@ defmodule Microwaveprop.Workers.WeatherFetchWorker do
   alias Microwaveprop.Weather.IemClient
   alias Microwaveprop.Weather.SoundingParams
   alias Microwaveprop.Weather.Station
+  alias Microwaveprop.Weather.SurfaceObservation
 
   require Logger
 
@@ -50,6 +51,15 @@ defmodule Microwaveprop.Workers.WeatherFetchWorker do
                 if row.observed_at, do: Weather.upsert_surface_observation(station, row)
               end)
 
+              # Store stub so this station/window isn't retried on future backfills
+              if count == 0 do
+                midpoint = DateTime.add(start_dt, div(DateTime.diff(end_dt, start_dt), 2))
+
+                %SurfaceObservation{}
+                |> SurfaceObservation.changeset(%{station_id: station.id, observed_at: midpoint})
+                |> Repo.insert(on_conflict: :nothing, conflict_target: [:station_id, :observed_at])
+              end
+
               Logger.info("WeatherFetch ASOS: #{station_code} ingested #{count} observations")
 
               Phoenix.PubSub.broadcast(
@@ -132,7 +142,14 @@ defmodule Microwaveprop.Workers.WeatherFetchWorker do
               :ok
 
             {:ok, []} ->
-              Logger.info("WeatherFetch RAOB: #{station_code} returned no data for #{sounding_time_str}")
+              # Store stub sounding so this station/time isn't retried on future backfills
+              Weather.upsert_sounding(station, %{
+                observed_at: sounding_time,
+                profile: [],
+                level_count: 0
+              })
+
+              Logger.info("WeatherFetch RAOB: #{station_code} no data for #{sounding_time_str}, stored stub")
               :ok
 
             {:error, reason} ->

test/microwaveprop/workers/iemre_fetch_worker_test.exs

@@ -60,7 +60,7 @@ defmodule Microwaveprop.Workers.IemreFetchWorkerTest do
       assert length(obs.hourly) == 2
     end
 
-    test "returns :ok on empty data" do
+    test "stores stub on empty data so backfill doesn't retry" do
       Req.Test.stub(IemClient, fn conn ->
         Req.Test.json(conn, %{"data" => []})
       end)
@@ -74,7 +74,12 @@ defmodule Microwaveprop.Workers.IemreFetchWorkerTest do
       }
 
       assert :ok = IemreFetchWorker.perform(job)
-      assert Repo.aggregate(IemreObservation, :count) == 0
+      assert Repo.aggregate(IemreObservation, :count) == 1
+
+      obs = Repo.one!(IemreObservation)
+      assert obs.hourly == []
+      assert obs.lat == 32.875
+      assert obs.lon == -97.0
     end
 
     test "retries on transient server error" do

test/microwaveprop/workers/weather_fetch_worker_test.exs

@@ -122,6 +122,33 @@ defmodule Microwaveprop.Workers.WeatherFetchWorkerTest do
       assert {:error, "IEM ASOS HTTP 503"} = WeatherFetchWorker.perform(%Oban.Job{args: args})
     end
 
+    test "stores stub observation on empty ASOS data so backfill doesn't retry", %{station: station} do
+      Req.Test.stub(IemClient, fn conn ->
+        body = """
+        #DEBUG,
+        station,valid,tmpf,dwpf,relh,sknt,drct,mslp,alti,skyc1,p01i,wxcodes
+        """
+
+        Plug.Conn.send_resp(conn, 200, body)
+      end)
+
+      args = %{
+        "fetch_type" => "asos",
+        "station_id" => station.id,
+        "station_code" => "KORD",
+        "start_dt" => "2026-03-28T16:53:00Z",
+        "end_dt" => "2026-03-28T20:53:00Z"
+      }
+
+      assert :ok = WeatherFetchWorker.perform(%Oban.Job{args: args})
+      assert Repo.aggregate(SurfaceObservation, :count) == 1
+
+      obs = Repo.one!(SurfaceObservation)
+      assert obs.station_id == station.id
+      # All weather fields nil — it's a stub
+      assert is_nil(obs.temp_f)
+    end
+
     test "returns :ok when station no longer exists" do
       Req.Test.stub(IemClient, fn conn ->
         Plug.Conn.send_resp(conn, 500, "Should not be called")
@@ -185,7 +212,7 @@ defmodule Microwaveprop.Workers.WeatherFetchWorkerTest do
       assert Repo.aggregate(Sounding, :count) == 1
     end
 
-    test "handles empty profiles", %{station: station} do
+    test "stores stub sounding on empty profiles so backfill doesn't retry", %{station: station} do
       Req.Test.stub(IemClient, fn conn ->
         Req.Test.json(conn, %{"profiles" => []})
       end)
@@ -198,7 +225,12 @@ defmodule Microwaveprop.Workers.WeatherFetchWorkerTest do
       }
 
       assert :ok = WeatherFetchWorker.perform(%Oban.Job{args: args})
-      assert Repo.aggregate(Sounding, :count) == 0
+      assert Repo.aggregate(Sounding, :count) == 1
+
+      sounding = Repo.one!(Sounding)
+      assert sounding.profile == []
+      assert sounding.level_count == 0
+      assert sounding.station_id == station.id
     end
 
     test "returns error on HTTP failure", %{station: station} do