Optimize presence and rate limit pings

assets/js/app.js

@@ -183,7 +183,7 @@ Hooks.Ping = {
     this.handleEvent("pong", () => {
       let rtt = Date.now() - this.nowMs
       this.el.innerText = `ping: ${rtt}ms`
-      this.timer = setTimeout(() => this.ping(rtt), 1000)
+      this.timer = setTimeout(() => this.ping(rtt), 100)
     })
     this.ping(null)
   },

lib/live_beats_web/channels/presence.ex

@@ -13,6 +13,7 @@ defmodule LiveBeatsWeb.Presence do
   import LiveBeatsWeb.LiveHelpers
 
   alias LiveBeats.{Accounts, MediaLibrary}
+  alias LiveBeatsWeb.Presence.BadgeComponent
 
   def subscribe(%MediaLibrary.Profile{} = profile) do
     LiveBeats.PresenceClient.subscribe(profile)
@@ -29,57 +30,79 @@ defmodule LiveBeatsWeb.Presence do
       {key, %{metas: metas, user: users[String.to_integer(key)]}}
     end
   end
-end
 
-defmodule LiveBeatsWeb.Presence.BadgeListComponent do
-  use LiveBeatsWeb, :live_component
+  def listening_now(assigns) do
+    import Phoenix.LiveView
+    count = Enum.count(assigns.presence_ids)
+
+    assigns =
+      assigns
+      |> assign(:count, count)
+      |> assign_new(:total_count, fn -> count end)
 
-  def render(assigns) do
     ~H"""
     <div class="px-4 mt-6 sm:px-6 lg:px-8"> <!-- users -->
-      <h2 class="text-gray-500 text-xs font-medium uppercase tracking-wide">Listening now</h2>
+      <h2 class="text-gray-500 text-xs font-medium uppercase tracking-wide">Listening now (<%= @count %>)</h2>
       <ul
         id="listening-now"
-        phx-update="prepend"
         role="list"
         x-max="1"
         class="grid grid-cols-1 gap-4 sm:gap-4 sm:grid-cols-2 xl:grid-cols-5 mt-3"
       >
-        <%= for presence <- @presences do %>
-          <li id={"presence-#{presence.id}"} class="relative col-span-1 flex shadow-sm rounded-md overflow-hidden">
-            <.link navigate={profile_path(presence)} class="flex-1 flex items-center justify-between border-t border-r border-b border-gray-200 bg-white rounded-r-md truncate">
-              <img class="w-12 h-12 flex-shrink-0 flex items-center justify-center rounded-l-md bg-purple-600" src={presence.avatar_url} alt="">
-              <div class="flex-1 flex items-center justify-between text-gray-900 text-sm font-medium hover:text-gray-600 pl-3">
-                <div class="flex-1 py-1 text-sm truncate">
-                  <%= render_slot(@inner_block, %{user: presence, ping: @pings[presence.id], region: @regions[presence.id]}) %>
-                </div>
-              </div>
-            </.link>
-          </li>
+        <%= for {id, _time} <- Enum.sort(@presence_ids, fn {_, t1}, {_, t2} -> t1 < t2 end) do %>
+          <.live_component
+            id={id}
+            module={BadgeComponent}
+            presence={@presences[id]}
+          />
         <% end %>
       </ul>
+      <%= if @total_count > @count do %>
+        <p>+ <%= @total_count - @count %> more</p>
+      <% end %>
     </div>
     """
   end
+end
+
+defmodule LiveBeatsWeb.Presence.BadgeComponent do
+  use LiveBeatsWeb, :live_component
+
+  def render(assigns) do
+    ~H"""
+    <li id={"presence-#{@id}"} class="relative col-span-1 flex shadow-sm rounded-md overflow-hidden">
+      <.link navigate={profile_path(@presence)} class="flex-1 flex items-center justify-between border-t border-r border-b border-gray-200 bg-white rounded-r-md truncate">
+        <img class="w-12 h-12 flex-shrink-0 flex items-center justify-center rounded-l-md bg-purple-600" src={@presence.avatar_url} alt="">
+        <div class="flex-1 flex items-center justify-between text-gray-900 text-sm font-medium hover:text-gray-600 pl-3">
+          <div class="flex-1 py-1 text-sm truncate">
+            <%= @presence.username %>
+            <%= if @ping do %>
+              <p class="text-gray-400 text-xs">ping: <%= @ping %>ms</p>
+              <%= if @region do %><img class="inline w-7 h-7 absolute right-3 top-3" src={"https://fly.io/ui/images/#{@region}.svg"} /><% end %>
+            <% end %>
+          </div>
+        </div>
+      </.link>
+    </li>
+    """
+  end
 
   def mount(socket) do
-    {:ok, socket, temporary_assigns: [presences: [], pings: %{}, regions: %{}]}
+    {:ok, socket, temporary_assigns: [presence: nil, ping: nil, region: nil]}
   end
 
   def update(%{action: {:ping, action}}, socket) do
     %{user: user, ping: ping, region: region} = action
 
-    {:ok,
-     socket
-     |> assign(:presences, [user])
-     |> update(:pings, &Map.put(&1, user.id, ping))
-     |> update(:regions, &Map.put(&1, user.id, region))}
+    {:ok, assign(socket, presence: user, ping: ping, region: region)}
   end
 
+  def update(%{presence: nil}, socket), do: {:ok, socket}
+
   def update(assigns, socket) do
     {:ok,
      socket
-     |> assign(assigns)
+     |> assign(id: assigns.id, presence: assigns.presence)
      |> assign_new(:pings, fn -> %{} end)
      |> assign_new(:regions, fn -> %{} end)}
   end

lib/live_beats_web/live/live_helpers.ex

@@ -13,12 +13,16 @@ defmodule LiveBeatsWeb.LiveHelpers do
 
   def profile_path(current_user_or_profile, action \\ :show)
 
+  def profile_path(username, action) when is_binary(username) do
+    Routes.profile_path(LiveBeatsWeb.Endpoint, action, username)
+  end
+
   def profile_path(%Accounts.User{} = current_user, action) do
-    Routes.profile_path(LiveBeatsWeb.Endpoint, action, current_user.username)
+    profile_path(current_user.username, action)
   end
 
   def profile_path(%MediaLibrary.Profile{} = profile, action) do
-    Routes.profile_path(LiveBeatsWeb.Endpoint, action, profile.username)
+    profile_path(profile.username, action)
   end
 
   def connection_status(assigns) do
@@ -134,12 +138,13 @@ defmodule LiveBeatsWeb.LiveHelpers do
     """
   end
 
-  def link(%{navigate: to} = assigns) do
-    opts = assigns |> assigns_to_attributes() |> Keyword.put(:to, to)
-    assigns = assign(assigns, :opts, opts)
+  def link(%{navigate: _to} = assigns) do
+    assigns = assign_new(assigns, :class, fn -> nil end)
 
     ~H"""
-    <%= live_redirect @opts do %><%= render_slot(@inner_block) %><% end %>
+    <a href={@navigate} data-phx-link="redirect" data-phx-link-state="push" class={@class}>
+      <%= render_slot(@inner_block) %>
+    </a>
     """
   end
 

lib/live_beats_web/live/nav.ex

@@ -1,7 +1,7 @@
 defmodule LiveBeatsWeb.Nav do
   import Phoenix.LiveView
 
-  alias LiveBeats.MediaLibrary
+  alias LiveBeats.{Accounts, MediaLibrary}
   alias LiveBeatsWeb.{ProfileLive, SettingsLive}
 
   def on_mount(:default, _params, _session, socket) do
@@ -32,15 +32,26 @@ defmodule LiveBeatsWeb.Nav do
   end
 
   defp handle_event("ping", %{"rtt" => rtt}, socket) do
-    %{current_user: current_user} = socket.assigns
-
-    if rtt && current_user && current_user.active_profile_user_id do
-      MediaLibrary.broadcast_ping(current_user, rtt, socket.assigns.region)
-    end
-
-    {:halt, push_event(socket, "pong", %{})}
+    {:halt,
+     socket
+     |> rate_limited_ping_broadcast(socket.assigns.current_user, rtt)
+     |> push_event("pong", %{})}
   end
 
+  defp rate_limited_ping_broadcast(socket, %Accounts.User{} = user, rtt) when is_integer(rtt) do
+    now = System.system_time(:millisecond)
+    last_ping_at = socket.assigns[:last_ping_at]
+
+    if is_nil(last_ping_at) || now - last_ping_at > 1000 do
+      MediaLibrary.broadcast_ping(user, rtt, socket.assigns.region)
+      assign(socket, :last_ping_at, now)
+    else
+      socket
+    end
+  end
+
+  defp rate_limited_ping_broadcast(socket, _user, _rtt), do: socket
+
   defp handle_event(_, _, socket), do: {:cont, socket}
 
   defp current_user_profile_username(socket) do

lib/live_beats_web/live/profile_live.ex

@@ -5,6 +5,8 @@ defmodule LiveBeatsWeb.ProfileLive do
   alias LiveBeatsWeb.{LayoutComponent, Presence}
   alias LiveBeatsWeb.ProfileLive.{SongRowComponent, UploadFormComponent}
 
+  @max_presences 20
+
   def render(assigns) do
     ~H"""
     <.title_bar>
@@ -39,17 +41,11 @@ defmodule LiveBeatsWeb.ProfileLive do
       </:actions>
     </.title_bar>
 
-    <.live_component
-      let={%{user: user, ping: ping, region: region}}
-      id={:presence_badges} module={Presence.BadgeListComponent}
+    <Presence.listening_now
       presences={@presences}
-    >
-      <%= user.username %>
-      <%= if ping do %>
-        <p class="text-gray-400 text-xs">ping: <%= ping %>ms</p>
-        <%= if region do %><img class="inline w-7 h-7 absolute right-3 top-3" src={"https://fly.io/ui/images/#{region}.svg"} /><% end %>
-      <% end %>
-    </.live_component>
+      presence_ids={@presence_ids}
+      total_count={@presences_count}
+    />
 
     <div id="dialogs" phx-update="append">
       <%= for song <- if(@owns_profile?, do: @songs, else: []), id = "delete-modal-#{song.id}" do %>
@@ -115,7 +111,7 @@ defmodule LiveBeatsWeb.ProfileLive do
       |> list_songs()
       |> assign_presences()
 
-    {:ok, socket, temporary_assigns: [songs: [], presences: []]}
+    {:ok, socket, temporary_assigns: [songs: [], presences: %{}]}
   end
 
   def handle_params(params, _url, socket) do
@@ -152,15 +148,14 @@ defmodule LiveBeatsWeb.ProfileLive do
   end
 
   def handle_info({LiveBeats.PresenceClient, %{user_joined: presence}}, socket) do
-    %{user: user} = presence
-    {:noreply, update(socket, :presences, &[user | &1])}
+    {:noreply, assign_presence(socket, presence)}
   end
 
   def handle_info({LiveBeats.PresenceClient, %{user_left: presence}}, socket) do
     %{user: user} = presence
 
     if presence.metas == [] do
-      {:noreply, push_event(socket, "remove-el", %{id: "presence-#{user.id}"})}
+      {:noreply, remove_presence(socket, user)}
     else
       {:noreply, socket}
     end
@@ -191,8 +186,9 @@ defmodule LiveBeatsWeb.ProfileLive do
 
   def handle_info({MediaLibrary, {:ping, ping}}, socket) do
     %{user: user, rtt: rtt, region: region} = ping
-    send_update(Presence.BadgeListComponent,
-      id: :presence_badges,
+
+    send_update(Presence.BadgeComponent,
+      id: user.id,
       action: {:ping, %{user: user, ping: rtt, region: region}}
     )
 
@@ -276,18 +272,43 @@ defmodule LiveBeatsWeb.ProfileLive do
   end
 
   defp assign_presences(socket) do
-    if profile = socket.assigns.profile do
-      presences =
-        profile
-        |> LiveBeats.PresenceClient.list()
-        |> Enum.map(fn {_key, meta} -> meta.user end)
+    socket = assign(socket, presences_count: 0, presences: %{}, presence_ids: %{})
 
-      assign(socket, presences: presences)
+    if profile = connected?(socket) && socket.assigns.profile do
+      profile
+      |> LiveBeats.PresenceClient.list()
+      |> Enum.reduce(socket, fn {_, presence}, acc -> assign_presence(acc, presence) end)
     else
-      assign(socket, presences: [])
+      socket
     end
   end
 
+  defp assign_presence(socket, presence) do
+    %{user: user} = presence
+    %{presence_ids: presence_ids} = socket.assigns
+
+    cond do
+      Map.has_key?(presence_ids, user.id) ->
+        socket
+
+      Enum.count(presence_ids) < @max_presences ->
+        socket
+        |> update(:presences, &Map.put(&1, user.id, user))
+        |> update(:presence_ids, &Map.put(&1, user.id, System.system_time()))
+        |> update(:presences_count, &(&1 + 1))
+
+      true ->
+        update(socket, :presences_count, &(&1 + 1))
+    end
+  end
+
+  defp remove_presence(socket, user) do
+    socket
+    |> update(:presences, &Map.delete(&1, user.id))
+    |> update(:presence_ids, &Map.delete(&1, user.id))
+    |> update(:presences_count, &(&1 - 1))
+  end
+
   defp url_text(nil), do: ""
 
   defp url_text(url_str) do