perf: batch high-frequency LiveView updates via socket.private

Buffer incoming packets in socket.private (no rerender) and flush to
assigns/stream on a 150ms timer, preventing client-side morphdom from
being overwhelmed during traffic bursts. Applies to the global packet
feed (stream) and per-callsign detail view (assigns).

lib/aprsme_web/live/packets_live/callsign_view.ex

@@ -11,6 +11,8 @@ defmodule AprsmeWeb.PacketsLive.CallsignView do
   alias Aprsme.Repo
   alias AprsmeWeb.Live.SharedPacketHandler
 
+  @flush_interval_ms 150
+
   @impl true
   def mount(%{"callsign" => callsign}, _session, socket) do
     normalized = Callsign.normalize(callsign)
@@ -40,6 +42,8 @@ defmodule AprsmeWeb.PacketsLive.CallsignView do
     |> assign(:live_packets, [])
     |> assign(:all_packets, stored)
     |> assign(:error, nil)
+    |> put_private(:packet_buffer, [])
+    |> put_private(:flush_timer, nil)
   end
 
   defp assign_invalid(socket, callsign) do
@@ -53,28 +57,52 @@ defmodule AprsmeWeb.PacketsLive.CallsignView do
 
   @impl true
   def handle_info({:postgres_packet, payload}, socket) do
-    SharedPacketHandler.handle_packet_update(payload, socket,
-      filter_fn: fn _packet, _socket -> true end,
-      process_fn: &process_matching_packet/2
-    )
+    # Buffer in socket.private to avoid triggering a rerender on every packet.
+    # A periodic flush timer drains the buffer and updates assigns in one batch,
+    # which keeps client-side morphdom from being overwhelmed during high-traffic bursts.
+    socket = update_in(socket.private.packet_buffer, &[payload | &1])
+    socket = ensure_flush_timer(socket)
+    {:noreply, socket}
+  end
+
+  @impl true
+  def handle_info(:flush_packets, socket) do
+    packets = Enum.reverse(socket.private.packet_buffer)
+    socket = put_private(socket, :packet_buffer, [])
+    socket = put_private(socket, :flush_timer, nil)
+
+    {updated_stored, updated_live} =
+      packets
+      # Sanitize encoding first, then batch enrich with device info
+      # (enrich_packets_with_device_info batches device lookups internally)
+      |> Enum.map(&EncodingUtils.sanitize_packet/1)
+      |> SharedPacketHandler.enrich_packets_with_device_info()
+      # Add canonical device identifier per-packet
+      |> Enum.map(&enrich_packet_with_device_identifier/1)
+      # Accumulate through the packet list update logic
+      |> Enum.reduce({socket.assigns.packets, socket.assigns.live_packets}, fn enriched, {stored, live} ->
+        update_packet_lists(stored, live, enriched)
+      end)
+
+    all_packets = get_all_packets_list(updated_stored, updated_live)
+
+    {:noreply,
+     assign(socket,
+       packets: updated_stored,
+       live_packets: updated_live,
+       all_packets: all_packets
+     )}
   end
 
   def handle_info(_message, socket), do: {:noreply, socket}
 
-  defp process_matching_packet(enriched_payload, socket) do
-    enriched_payload = enrich_packet_with_device_identifier(enriched_payload)
-
-    current_live = socket.assigns.live_packets
-    current_stored = socket.assigns.packets
-
-    {updated_stored, updated_live} = update_packet_lists(current_stored, current_live, enriched_payload)
-    all_packets = get_all_packets_list(updated_stored, updated_live)
-
-    {:noreply,
-     socket
-     |> assign(:packets, updated_stored)
-     |> assign(:live_packets, updated_live)
-     |> assign(:all_packets, all_packets)}
+  defp ensure_flush_timer(socket) do
+    if socket.private.flush_timer do
+      socket
+    else
+      timer = Process.send_after(self(), :flush_packets, @flush_interval_ms)
+      put_private(socket, :flush_timer, timer)
+    end
   end
 
   defp enrich_packet_with_device_identifier(sanitized_payload) do

lib/aprsme_web/live/packets_live/index.ex

@@ -5,37 +5,78 @@ defmodule AprsmeWeb.PacketsLive.Index do
 
   alias Aprsme.EncodingUtils
 
+  @flush_interval_ms 150
+  @max_stream_size 100
+
   @impl true
   def mount(_params, _session, socket) do
-    _ =
-      if connected?(socket) do
-        Phoenix.PubSub.subscribe(Aprsme.PubSub, "postgres:aprsme_packets")
-      end
+    if connected?(socket) do
+      Phoenix.PubSub.subscribe(Aprsme.PubSub, "postgres:aprsme_packets")
+    end
 
-    {:ok, stream(socket, :packets, [], at: 0)}
+    {:ok,
+     socket
+     |> put_private(:packet_buffer, [])
+     |> put_private(:flush_timer, nil)
+     |> stream(:packets, [], at: 0)}
   end
 
   @impl true
   def handle_info({:postgres_packet, payload}, socket) do
-    sanitized_payload = EncodingUtils.sanitize_packet(payload)
+    # Buffer in socket.private to avoid triggering a rerender on every packet.
+    # A periodic flush timer drains the buffer and batch-inserts into the stream,
+    # which keeps client-side morphdom from being overwhelmed during high-traffic bursts.
+    socket = update_in(socket.private.packet_buffer, &[payload | &1])
+    socket = ensure_flush_timer(socket)
+    {:noreply, socket}
+  end
 
+  @impl true
+  def handle_info(:flush_packets, socket) do
+    packets = Enum.reverse(socket.private.packet_buffer)
+    socket = put_private(socket, :packet_buffer, [])
+    socket = put_private(socket, :flush_timer, nil)
+
+    # Batch insert all accumulated packets into the stream.
+    # Processing newest-first with at: 0 preserves descending-chronological order.
     socket =
-      socket
-      |> stream_insert(:packets, sanitized_payload, at: 0)
-      |> then(fn s ->
-        stream = s.assigns.streams.packets
-
-        if Enum.count(stream) > 100 do
-          {id, _} = stream |> Enum.reverse() |> hd()
-          stream_delete(s, :packets, id)
-        else
-          s
-        end
+      Enum.reduce(packets, socket, fn payload, s ->
+        sanitized = EncodingUtils.sanitize_packet(payload)
+        stream_insert(s, :packets, sanitized, at: 0)
       end)
 
+    # Trim stream to keep at most @max_stream_size items.
+    socket = trim_stream(socket)
+
     {:noreply, socket}
   end
 
+  defp ensure_flush_timer(socket) do
+    if socket.private.flush_timer do
+      socket
+    else
+      timer = Process.send_after(self(), :flush_packets, @flush_interval_ms)
+      put_private(socket, :flush_timer, timer)
+    end
+  end
+
+  defp trim_stream(socket) do
+    stream = socket.assigns.streams.packets
+    count = Enum.count(stream)
+
+    if count > @max_stream_size do
+      excess = count - @max_stream_size
+      # Remove excess from the end (oldest items)
+      to_remove = stream |> Enum.reverse() |> Enum.take(excess)
+
+      Enum.reduce(to_remove, socket, fn {id, _}, s ->
+        stream_delete(s, :packets, id)
+      end)
+    else
+      socket
+    end
+  end
+
   @doc """
   Extract a coordinate (:lat or :lon) from a packet, checking multiple sources:
   1. Direct :lat/:lon keys