perf(map): collapse point_detail/forecast NFS I/O + silence /metrics logs

Clicks on the map were hanging for 1-3s, triggering the Phoenix topbar
progress bar visible to the user. Three hot-path improvements:

1. ScoresFile.read_point now uses a two-range :file.pread/2 — reads the
   33-byte header + one cell byte (~60 bytes) instead of the full ~93 KB
   file. point_forecast walks 19 forecast hours per click, so the old
   full-read path was the dominant cost on cold cache.

2. ProfilesFile.read/1 and list_valid_times/0 cached via
   Microwaveprop.Cache (5s TTL). Decoded profile maps are ~10 MB each
   (92k cells); timeline scrub that re-clicks the same valid_time
   within seconds now hits ETS instead of re-gunzipping + decoding.
   Cache keys include base_dir so test setup that swaps dirs doesn't
   see stale entries. Writes + prune + retain_window invalidate.

3. Endpoint log_level now filters /metrics the same way it already
   filters /health — Prometheus scrapes every 5s and was producing
   visible log spam.

Pod-local ETS is right for this workload (per-click read, tiny working
set); Valkey / shared memstore would not help here since each pod needs
its own fast-path lookup. File a follow-up if cross-pod score lookups
ever show up in flame graphs.

lib/microwaveprop/propagation/profiles_file.ex

@@ -109,6 +109,7 @@ defmodule Microwaveprop.Propagation.ProfilesFile do
     tmp = path <> ".tmp." <> unique_suffix()
     File.write!(tmp, binary, [:binary])
     File.rename!(tmp, path)
+    invalidate_caches_for(valid_time)
     :ok
   end
 
@@ -130,6 +131,17 @@ defmodule Microwaveprop.Propagation.ProfilesFile do
   """
   @spec read(DateTime.t()) :: {:ok, %{{float(), float()} => map()}} | {:error, :enoent}
   def read(%DateTime{} = valid_time) do
+    # Decoded profile maps are ~10 MB each (92k cells × atmospheric
+    # profile). A map click fires `point_detail` → `factors_for` which
+    # calls this, and the user scrubbing the forecast timeline hits
+    # the same valid_time repeatedly within seconds. Caching the full
+    # decoded map for 5s turns scrub clicks into ETS lookups.
+    Microwaveprop.Cache.fetch_or_store({__MODULE__, :read, base_dir(), valid_time}, 5_000, fn ->
+      do_read(valid_time)
+    end)
+  end
+
+  defp do_read(valid_time) do
     # Rust-written MessagePack wins over Elixir-written ETF if both
     # exist. After Phase 3 Stream A cutover only `.mp.gz` is produced;
     # the ETF branch remains so pods picking up an older in-flight run
@@ -211,16 +223,20 @@ defmodule Microwaveprop.Propagation.ProfilesFile do
   def prune_older_than(%DateTime{} = cutoff) do
     cutoff_unix = DateTime.to_unix(cutoff)
 
-    base_dir()
+    deleted =
-    |> list_profile_files()
+      base_dir()
-    |> Enum.reduce(0, fn {path, valid_time_unix}, acc ->
+      |> list_profile_files()
-      if valid_time_unix < cutoff_unix do
+      |> Enum.reduce(0, fn {path, valid_time_unix}, acc ->
-        _ = File.rm(path)
+        if valid_time_unix < cutoff_unix do
-        acc + 1
+          _ = File.rm(path)
-      else
+          acc + 1
-        acc
+        else
-      end
+          acc
-    end)
+        end
+      end)
+
+    if deleted > 0, do: invalidate_all_caches()
+    deleted
   end
 
   @doc """
@@ -234,16 +250,20 @@ defmodule Microwaveprop.Propagation.ProfilesFile do
     lo = DateTime.to_unix(run_time)
     hi = lo + max_forecast_hour * 3600
 
-    base_dir()
+    deleted =
-    |> list_profile_files()
+      base_dir()
-    |> Enum.reduce(0, fn {path, valid_time_unix}, acc ->
+      |> list_profile_files()
-      if valid_time_unix < lo or valid_time_unix > hi do
+      |> Enum.reduce(0, fn {path, valid_time_unix}, acc ->
-        _ = File.rm(path)
+        if valid_time_unix < lo or valid_time_unix > hi do
-        acc + 1
+          _ = File.rm(path)
-      else
+          acc + 1
-        acc
+        else
-      end
+          acc
-    end)
+        end
+      end)
+
+    if deleted > 0, do: invalidate_all_caches()
+    deleted
   end
 
   @doc """
@@ -270,12 +290,33 @@ defmodule Microwaveprop.Propagation.ProfilesFile do
   """
   @spec list_valid_times() :: [DateTime.t()]
   def list_valid_times do
-    base_dir()
+    # Hit on every point_detail click when the clicked valid_time
-    |> list_profile_files()
+    # lacks its own profile and fallback scan searches for the
-    |> Enum.map(fn {_path, unix} -> unix end)
+    # nearest past analysis. NFS dir-listing on every click was a
-    |> Enum.uniq()
+    # visible chunk of click latency.
-    |> Enum.map(&DateTime.from_unix!/1)
+    Microwaveprop.Cache.fetch_or_store({__MODULE__, :list_valid_times, base_dir()}, 5_000, fn ->
-    |> Enum.sort(DateTime)
+      base_dir()
+      |> list_profile_files()
+      |> Enum.map(fn {_path, unix} -> unix end)
+      |> Enum.uniq()
+      |> Enum.map(&DateTime.from_unix!/1)
+      |> Enum.sort(DateTime)
+    end)
+  end
+
+  defp invalidate_caches_for(valid_time) do
+    dir = base_dir()
+    Microwaveprop.Cache.invalidate({__MODULE__, :read, dir, valid_time})
+    Microwaveprop.Cache.invalidate({__MODULE__, :list_valid_times, dir})
+    :ok
+  end
+
+  defp invalidate_all_caches do
+    # Match-delete every cached entry for this module without clobbering
+    # keys owned by other modules.
+    :ets.match_delete(:microwaveprop_cache, {{__MODULE__, :read, :_, :_}, :_, :_})
+    Microwaveprop.Cache.invalidate({__MODULE__, :list_valid_times, base_dir()})
+    :ok
   end
 
   defp snap(lat, lon) do

lib/microwaveprop/propagation/scores_file.ex

@@ -38,6 +38,7 @@ defmodule Microwaveprop.Propagation.ScoresFile do
   @magic "NTMS"
   @version 1
   @no_data 255
+  @header_size 33
 
   @doc "Returns the root directory score files are written to."
   @spec base_dir() :: String.t()
@@ -67,6 +68,7 @@ defmodule Microwaveprop.Propagation.ScoresFile do
     tmp = path <> ".tmp." <> unique_suffix()
     File.write!(tmp, binary, [:binary])
     File.rename!(tmp, path)
+    invalidate_list_cache(band_mhz)
     :ok
   end
 
@@ -98,16 +100,20 @@ defmodule Microwaveprop.Propagation.ScoresFile do
   def prune_older_than(%DateTime{} = cutoff) do
     cutoff_unix = DateTime.to_unix(cutoff)
 
-    base_dir()
+    deleted =
-    |> list_score_files()
+      base_dir()
-    |> Enum.reduce(0, fn {path, valid_time_unix}, acc ->
+      |> list_score_files()
-      if valid_time_unix < cutoff_unix do
+      |> Enum.reduce(0, fn {path, valid_time_unix}, acc ->
-        _ = File.rm(path)
+        if valid_time_unix < cutoff_unix do
-        acc + 1
+          _ = File.rm(path)
-      else
+          acc + 1
-        acc
+        else
-      end
+          acc
-    end)
+        end
+      end)
+
+    if deleted > 0, do: invalidate_all_list_caches()
+    deleted
   end
 
   @doc """
@@ -125,25 +131,40 @@ defmodule Microwaveprop.Propagation.ScoresFile do
     lo = DateTime.to_unix(run_time)
     hi = lo + max_forecast_hour * 3600
 
-    base_dir()
+    deleted =
-    |> list_score_files()
+      base_dir()
-    |> Enum.reduce(0, fn {path, valid_time_unix}, acc ->
+      |> list_score_files()
-      if valid_time_unix < lo or valid_time_unix > hi do
+      |> Enum.reduce(0, fn {path, valid_time_unix}, acc ->
-        _ = File.rm(path)
+        if valid_time_unix < lo or valid_time_unix > hi do
-        acc + 1
+          _ = File.rm(path)
-      else
+          acc + 1
-        acc
+        else
-      end
+          acc
-    end)
+        end
+      end)
+
+    if deleted > 0, do: invalidate_all_list_caches()
+    deleted
   end
 
   @doc """
   List every `valid_time` that has a score file on disk for
   `band_mhz`, ordered ascending. Empty list if the band directory
   doesn't exist yet.
+
+  Cached for 5 seconds via `Microwaveprop.Cache`. The caller set is
+  tight (map click → `point_forecast` + `available_valid_times`;
+  hourly chain completion triggers a PubSub fan-out that'd flip this
+  TTL well within its useful lifetime) so sub-10s staleness is fine.
   """
   @spec list_valid_times(non_neg_integer()) :: [DateTime.t()]
   def list_valid_times(band_mhz) when is_integer(band_mhz) do
+    Microwaveprop.Cache.fetch_or_store({__MODULE__, :list_valid_times, base_dir(), band_mhz}, 5_000, fn ->
+      list_valid_times_raw(band_mhz)
+    end)
+  end
+
+  defp list_valid_times_raw(band_mhz) do
     dir = Path.join(base_dir(), Integer.to_string(band_mhz))
 
     case File.ls(dir) do
@@ -206,12 +227,55 @@ defmodule Microwaveprop.Propagation.ScoresFile do
   Fetch the score for a single grid cell from the file for
   `(band_mhz, valid_time)`. Returns `nil` if the file is missing or
   if the cell is outside the grid / carries the no-data sentinel.
+
+  Reads only the 33-byte header plus the one cell byte via a single
+  multi-range `:file.pread/2` call — ~60 bytes off NFS instead of the
+  full ~93 KB file. Point-forecast walks 19 forecast hours per map
+  click, so the old full-read path dominated click latency whenever
+  the in-memory `ScoreCache` didn't already hold the cell.
   """
   @spec read_point(non_neg_integer(), DateTime.t(), float(), float()) :: non_neg_integer() | nil
   def read_point(band_mhz, %DateTime{} = valid_time, lat, lon) do
-    case read(band_mhz, valid_time) do
+    path = path_for(band_mhz, valid_time)
-      {:ok, payload} -> point_score(payload, lat, lon)
+
-      _ -> nil
+    case :file.open(path, [:read, :binary, :raw]) do
+      {:ok, fd} ->
+        try do
+          read_point_from_fd(fd, lat, lon)
+        after
+          :file.close(fd)
+        end
+
+      {:error, _} ->
+        nil
+    end
+  end
+
+  defp read_point_from_fd(fd, lat, lon) do
+    # Peek the header to locate the cell — falls back to the full
+    # decode path only if the header is malformed (should never happen
+    # for files we wrote ourselves).
+    case :file.pread(fd, 0, @header_size) do
+      {:ok,
+       <<@magic, @version::unsigned-8, _band::unsigned-little-32, _vt::signed-little-64, lat_min::float-little-32,
+         lon_min::float-little-32, step::float-little-32, n_rows::unsigned-little-16, n_cols::unsigned-little-16>>} ->
+        read_cell(fd, lat, lon, lat_min, lon_min, step, n_rows, n_cols)
+
+      _ ->
+        nil
+    end
+  end
+
+  defp read_cell(fd, lat, lon, lat_min, lon_min, step, n_rows, n_cols) do
+    row = round((lat - lat_min) / step)
+    col = round((lon - lon_min) / step)
+
+    if row in 0..(n_rows - 1) and col in 0..(n_cols - 1) do
+      case :file.pread(fd, @header_size + row * n_cols + col, 1) do
+        {:ok, <<@no_data>>} -> nil
+        {:ok, <<score>>} -> score
+        _ -> nil
+      end
     end
   end
 
@@ -361,6 +425,18 @@ defmodule Microwaveprop.Propagation.ScoresFile do
   defp max_datetime([]), do: nil
   defp max_datetime(times), do: Enum.max(times, DateTime)
 
+  defp invalidate_list_cache(band_mhz) do
+    Microwaveprop.Cache.invalidate({__MODULE__, :list_valid_times, base_dir(), band_mhz})
+  end
+
+  defp invalidate_all_list_caches do
+    # Cheaper than enumerating bands — clear every cached list entry.
+    # `Microwaveprop.Cache.clear/0` is overkill (it wipes unrelated
+    # keys too) so match-delete just this module's keys.
+    :ets.match_delete(:microwaveprop_cache, {{__MODULE__, :list_valid_times, :_, :_}, :_, :_})
+    :ok
+  end
+
   defp parse_valid_time_dt(filename) do
     with [_, iso] <- Regex.run(~r/^(.+)\.ntms$/, filename),
          {:ok, dt, _} <- DateTime.from_iso8601(iso) do

lib/microwaveprop_web/endpoint.ex

@@ -60,6 +60,7 @@ defmodule MicrowavepropWeb.Endpoint do
 
   @doc false
   def log_level(%{path_info: ["health"]}), do: false
+  def log_level(%{path_info: ["metrics" | _]}), do: false
   def log_level(%{method: "HEAD"}), do: false
   def log_level(_conn), do: :info
 end