Add deployment notification system to update timestamp in LiveViews

When a new deployment occurs in k8s, all connected LiveViews now receive
a notification to update their deployment timestamp display.

Changes:
- Added DeploymentNotifier GenServer that broadcasts deployment events
- LiveViews subscribe to "deployment_events" PubSub topic
- When DEPLOYED_AT env var is set (k8s deployments), a notification is
  sent after app startup
- LiveViews handle the deployment event and update their timestamp

This ensures that when a new version is deployed, users see the
deployment timestamp update in real-time without needing to refresh
their browser.

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

lib/aprsme/application.ex

@@ -49,6 +49,8 @@ defmodule Aprsme.Application do
       Aprsme.CleanupScheduler,
       Aprsme.Presence,
       Aprsme.PostgresNotifier,
+      # Start deployment notifier
+      Aprsme.DeploymentNotifier,
       # Start the packet processing pipeline
       Aprsme.PacketPipelineSupervisor
     ]

lib/aprsme/deployment_notifier.ex

@@ -0,0 +1,62 @@
+defmodule Aprsme.DeploymentNotifier do
+  @moduledoc """
+  Monitors for deployment changes and notifies connected clients.
+  In k8s, this detects when the DEPLOYED_AT environment variable changes.
+  """
+  use GenServer
+
+  require Logger
+
+  @check_interval :timer.seconds(30)
+
+  def start_link(opts \\ []) do
+    GenServer.start_link(__MODULE__, opts, name: __MODULE__)
+  end
+
+  def init(_opts) do
+    # Schedule first check
+    Process.send_after(self(), :check_deployment, @check_interval)
+
+    # Get initial deployment timestamp
+    deployed_at = Aprsme.Release.deployed_at()
+
+    {:ok, %{deployed_at: deployed_at}}
+  end
+
+  def handle_info(:check_deployment, state) do
+    # Schedule next check
+    Process.send_after(self(), :check_deployment, @check_interval)
+
+    # Get current deployment timestamp
+    current_deployed_at = Aprsme.Release.deployed_at()
+
+    # Check if deployment timestamp changed (shouldn't happen in same process, but useful for monitoring)
+    if current_deployed_at == state.deployed_at do
+      {:noreply, state}
+
+      # Broadcast the new deployment
+    else
+      Logger.info("Deployment timestamp changed from #{state.deployed_at} to #{current_deployed_at}")
+
+      Phoenix.PubSub.broadcast(
+        Aprsme.PubSub,
+        "deployment_events",
+        {:new_deployment, %{deployed_at: current_deployed_at}}
+      )
+
+      {:noreply, %{state | deployed_at: current_deployed_at}}
+    end
+  end
+
+  @doc """
+  Notify about a new deployment immediately.
+  This can be called from the release module when deployment is detected.
+  """
+  def notify_deployment(deployed_at) do
+    Phoenix.PubSub.broadcast(
+      Aprsme.PubSub,
+      "deployment_events",
+      {:new_deployment, %{deployed_at: deployed_at}}
+    )
+  end
+end

lib/aprsme/release.ex

@@ -100,6 +100,27 @@ defmodule Aprsme.Release do
     # Store in application config
     Application.put_env(:aprsme, :deployed_at, deployed_at)
 
+    # Notify about deployment after a short delay to ensure PubSub is started
+    # In k8s, this will notify all connected clients about the new deployment
+    if System.get_env("DEPLOYED_AT") do
+      spawn(fn ->
+        # Wait for application to start
+        Process.sleep(10_000)
+
+        try do
+          require Logger
+
+          Aprsme.DeploymentNotifier.notify_deployment(deployed_at)
+          Logger.info("Deployment notification sent for timestamp: #{deployed_at}")
+        rescue
+          error ->
+            require Logger
+
+            Logger.warning("Failed to send deployment notification: #{inspect(error)}")
+        end
+      end)
+    end
+
     deployed_at
   end
 

lib/aprsme_web/live/map_live/index.ex

@@ -28,6 +28,7 @@ defmodule AprsmeWeb.MapLive.Index do
   alias AprsmeWeb.MapLive.UrlParams
   alias AprsmeWeb.TimeUtils
   alias Phoenix.LiveView.Socket
+  alias Phoenix.Socket.Broadcast
 
   @impl true
   def mount(params, session, socket) do
@@ -107,6 +108,9 @@ defmodule AprsmeWeb.MapLive.Index do
     # Still subscribe to bad packets (they don't have location)
     Phoenix.PubSub.subscribe(Aprsme.PubSub, "bad_packets")
 
+    # Subscribe to deployment events
+    Phoenix.PubSub.subscribe(Aprsme.PubSub, "deployment_events")
+
     # Subscribe to StreamingPacketsPubSub with initial bounds
     Aprsme.StreamingPacketsPubSub.subscribe_to_bounds(self(), default_bounds)
 
@@ -671,6 +675,13 @@ defmodule AprsmeWeb.MapLive.Index do
 
   def handle_info({:streaming_packet, packet}, socket), do: handle_info_postgres_packet(packet, socket)
 
+  def handle_info(
+        %Broadcast{topic: "deployment_events", payload: {:new_deployment, %{deployed_at: deployed_at}}},
+        socket
+      ) do
+    {:noreply, assign(socket, :deployed_at, deployed_at)}
+  end
+
   def handle_info({:load_rf_path_station_packets, stations}, socket) do
     # Load the most recent packet for each RF path station
     station_packets =
@@ -722,7 +733,7 @@ defmodule AprsmeWeb.MapLive.Index do
     end
   end
 
-  def handle_info(%Phoenix.Socket.Broadcast{topic: "aprs_messages", event: "packet", payload: packet}, socket),
+  def handle_info(%Broadcast{topic: "aprs_messages", event: "packet", payload: packet}, socket),
     do: handle_info({:postgres_packet, packet}, socket)
 
   def handle_info({:show_error, message}, socket) do