fix: egress measurement

Author: filipecabaco

README.md

@@ -194,6 +194,8 @@ If you're using the default tenant, the URL is `ws://realtime-dev.localhost:4000
 | BROADCAST_POOL_SIZE                             | number  | Number of processes to relay Phoenix.PubSub messages across the cluster                                                                                                                                                                                                                                                         |
 | POSTGRES_CDC_SCOPE_SHARDS                       | number  | Number of dynamic supervisor partitions used by the Postgres CDC extension. Defaults to 5.                                                                                                                                                                                                                                      |
 | USERS_SCOPE_SHARDS                              | number  | Number of dynamic supervisor partitions used by the Users extension. Defaults to 5.                                                                                                                                                                                                                                             |
+| NO_CHANNEL_TIMEOUT_IN_MS                        | number  | Time in ms to check if a socket has no channels open and if so, disconnect it. Defaults to 10 minutes.                                                                                                                                                                                                                         |
+| EGRESS_TELEMETRY_INTERVAL_IN_MS                 | number  | Time in ms to send telemetry for egress. Defaults to 15 seconds.                                                                                                                                                                                                                                                               |
 
 The OpenTelemetry variables mentioned above are not an exhaustive list of all [supported environment variables](https://opentelemetry.io/docs/languages/sdk-configuration/).
 

config/runtime.exs

@@ -73,6 +73,7 @@ websocket_max_heap_size = div(Env.get_integer("WEBSOCKET_MAX_HEAP_SIZE", 50_000_
 users_scope_shards = Env.get_integer("USERS_SCOPE_SHARDS", 5)
 postgres_cdc_scope_shards = Env.get_integer("POSTGRES_CDC_SCOPE_SHARDS", 5)
 regional_broadcasting = Env.get_boolean("REGIONAL_BROADCASTING", false)
+egress_telemetry_interval_in_ms = Env.get_integer("EGRESS_TELEMETRY_INTERVAL_IN_MS", :timer.seconds(15))
 no_channel_timeout_in_ms = Env.get_integer("NO_CHANNEL_TIMEOUT_IN_MS", :timer.minutes(10))
 
 if !(db_version in [nil, "ipv6", "ipv4"]),
@@ -122,13 +123,14 @@ config :realtime,
   tenant_cache_expiration: tenant_cache_expiration,
   rpc_timeout: rpc_timeout,
   max_gen_rpc_clients: max_gen_rpc_clients,
-  no_channel_timeout_in_ms: no_channel_timeout_in_ms,
   platform: platform,
   pubsub_adapter: pubsub_adapter,
   broadcast_pool_size: broadcast_pool_size,
   users_scope_shards: users_scope_shards,
   postgres_cdc_scope_shards: postgres_cdc_scope_shards,
-  regional_broadcasting: regional_broadcasting
+  regional_broadcasting: regional_broadcasting,
+  egress_telemetry_interval_in_ms: egress_telemetry_interval_in_ms,
+  no_channel_timeout_in_ms: no_channel_timeout_in_ms
 
 if config_env() != :test && run_janitor? do
   config :realtime,

lib/realtime/application.ex

@@ -55,6 +55,7 @@ defmodule Realtime.Application do
     migration_partition_slots = Application.get_env(:realtime, :migration_partition_slots)
     connect_partition_slots = Application.get_env(:realtime, :connect_partition_slots)
     no_channel_timeout_in_ms = Application.get_env(:realtime, :no_channel_timeout_in_ms)
+    egress_telemetry_interval_in_ms = Application.get_env(:realtime, :egress_telemetry_interval_in_ms)
 
     children =
       [
@@ -94,7 +95,9 @@ defmodule Realtime.Application do
          strategy: :one_for_one,
          name: Connect.DynamicSupervisor,
          partitions: connect_partition_slots},
-        {RealtimeWeb.RealtimeChannel.Tracker, check_interval_in_ms: no_channel_timeout_in_ms},
+        {RealtimeWeb.RealtimeChannel.Tracker,
+         no_channel_timeout_in_ms: no_channel_timeout_in_ms,
+         egress_telemetry_interval_in_ms: egress_telemetry_interval_in_ms},
         RealtimeWeb.Endpoint,
         RealtimeWeb.Presence
       ] ++ extensions_supervisors() ++ janitor_tasks()

lib/realtime/monitoring/prom_ex/plugins/tenant.ex

@@ -23,10 +23,26 @@ defmodule Realtime.PromEx.Plugins.Tenant do
       channel_events(),
       replication_metrics(),
       subscription_metrics(),
-      payload_size_metrics()
+      payload_size_metrics(),
+      output_bytes_metrics()
     ]
   end
 
+  defp output_bytes_metrics do
+    Event.build(
+      :realtime_connections_output_bytes_metrics,
+      [
+        last_value(
+          [:realtime, :connections, :output_bytes],
+          event_name: [:realtime, :connections, :output_bytes],
+          description: "The total count of output bytes for a tenant.",
+          measurement: :output_bytes,
+          tags: [:tenant]
+        )
+      ]
+    )
+  end
+
   defp payload_size_metrics do
     Event.build(
       :realtime_tenant_payload_size_metrics,

lib/realtime_web/channels/realtime_channel.ex

@@ -45,7 +45,7 @@ defmodule RealtimeWeb.RealtimeChannel do
 
     Process.flag(:max_heap_size, max_heap_size())
     Process.flag(:fullsweep_after, @fullsweep_after)
-    Tracker.track(socket.transport_pid)
+    Tracker.track(socket.transport_pid, tenant_id)
     Logger.metadata(external_id: tenant_id, project: tenant_id)
     Logger.put_process_level(self(), log_level)
 
@@ -499,10 +499,10 @@ defmodule RealtimeWeb.RealtimeChannel do
   end
 
   @impl true
-  def terminate(reason, %{transport_pid: transport_pid}) do
+  def terminate(reason, %{transport_pid: transport_pid, assigns: %{tenant: tenant_id}}) do
     Logger.debug("Channel terminated with reason: #{reason}")
     :telemetry.execute([:prom_ex, :plugin, :realtime, :disconnected], %{})
-    Tracker.untrack(transport_pid)
+    Tracker.untrack(transport_pid, tenant_id)
     :ok
   end
 

lib/realtime_web/channels/realtime_channel/tracker.ex

@@ -8,29 +8,41 @@ defmodule RealtimeWeb.RealtimeChannel.Tracker do
   """
   use GenServer
   require Logger
+  alias Realtime.Helpers
+
+  defstruct [
+    :no_channel_timeout_in_ms,
+    :no_channel_timeout_ref,
+    :egress_telemetry_interval_in_ms,
+    :egress_telemetry_ref
+  ]
 
   @table :channel_tracker
-  @zero_count_match [{{:"$1", :"$2"}, [{:"=<", :"$2", 0}], [:"$1"]}]
-  @zero_count_delete [{{:"$1", :"$2"}, [{:"=<", :"$2", 0}], [true]}]
+  @zero_count_match [{{{:"$1", :_}, :"$2"}, [{:"=<", :"$2", 0}], [:"$1"]}]
+  @zero_count_delete [{{{:"$1", :_}, :"$2"}, [{:"=<", :"$2", 0}], [true]}]
+  @egress_telemetry_match [{{{:"$1", :"$2"}, :"$3"}, [{:>, :"$3", 0}], [[:"$1", :"$2"]]}]
+
   @doc """
   Tracks a transport pid.
   """
-  @spec track(pid()) :: integer()
-  def track(pid), do: :ets.update_counter(@table, pid, 1, {pid, 0})
+  @spec track(pid(), binary()) :: integer()
+  def track(pid, tenant_external_id),
+    do: :ets.update_counter(@table, {pid, tenant_external_id}, 1, {{pid, tenant_external_id}, 0})
 
   @doc """
   Un-tracks a transport pid.
   """
-  @spec untrack(pid()) :: integer()
-  def untrack(pid), do: :ets.update_counter(@table, pid, -1, {pid, 0})
+  @spec untrack(pid(), binary()) :: integer()
+  def untrack(pid, tenant_external_id),
+    do: :ets.update_counter(@table, {pid, tenant_external_id}, -1, {{pid, tenant_external_id}, 0})
 
   @doc """
   Returns the number of channels open for a transport pid.
   """
-  @spec count(pid()) :: integer()
-  def count(pid) do
-    case :ets.lookup(@table, pid) do
-      [{^pid, count}] -> count
+  @spec count(pid(), binary()) :: integer()
+  def count(pid, tenant_external_id) do
+    case :ets.lookup(@table, {pid, tenant_external_id}) do
+      [{{^pid, ^tenant_external_id}, count}] -> count
       [] -> 0
     end
   end
@@ -57,17 +69,54 @@ defmodule RealtimeWeb.RealtimeChannel.Tracker do
 
   @impl true
   def init(opts) do
-    check_interval_in_ms = Keyword.fetch!(opts, :check_interval_in_ms)
-    Process.send_after(self(), :check_channels, check_interval_in_ms)
-    {:ok, %{check_interval_in_ms: check_interval_in_ms}}
+    no_channel_timeout_in_ms = Keyword.fetch!(opts, :no_channel_timeout_in_ms)
+    no_channel_timeout_ref = Process.send_after(self(), :check_channels, no_channel_timeout_in_ms)
+    egress_telemetry_interval_in_ms = Keyword.fetch!(opts, :egress_telemetry_interval_in_ms)
+    egress_telemetry_ref = Process.send_after(self(), :send_egress_telemetry, egress_telemetry_interval_in_ms)
+
+    {:ok,
+     %{
+       no_channel_timeout_in_ms: no_channel_timeout_in_ms,
+       no_channel_timeout_ref: no_channel_timeout_ref,
+       egress_telemetry_interval_in_ms: egress_telemetry_interval_in_ms,
+       egress_telemetry_ref: egress_telemetry_ref
+     }}
   end
 
   @impl true
   def handle_info(:check_channels, state) do
+    %{no_channel_timeout_ref: no_channel_timeout_ref, no_channel_timeout_in_ms: no_channel_timeout_in_ms} = state
     chunked_killing()
     :ets.select_delete(@table, @zero_count_delete)
-    Process.send_after(self(), :check_channels, state.check_interval_in_ms)
-    {:noreply, state}
+    Helpers.cancel_timer(no_channel_timeout_ref)
+    no_channel_timeout_ref = Process.send_after(self(), :check_channels, no_channel_timeout_in_ms)
+    {:noreply, %{state | no_channel_timeout_ref: no_channel_timeout_ref}}
+  end
+
+  def handle_info(:send_egress_telemetry, state) do
+    %{egress_telemetry_ref: egress_telemetry_ref, egress_telemetry_interval_in_ms: egress_telemetry_interval_in_ms} =
+      state
+
+    Port.list()
+    |> Enum.flat_map(fn port ->
+      case Port.info(port, :links) do
+        {:links, pids} -> Enum.map(pids, fn pid -> {pid, port} end)
+        _ -> []
+      end
+    end)
+    |> Enum.group_by(fn {pid, _} -> pid end, fn {_, port} -> port end)
+    |> collect_egress_telemetry()
+    |> Enum.each(fn {tenant_external_id, output_bytes} ->
+      if output_bytes > 0 do
+        :telemetry.execute([:realtime, :connections, :output_bytes], %{output_bytes: output_bytes}, %{
+          tenant_external_id: tenant_external_id
+        })
+      end
+    end)
+
+    Helpers.cancel_timer(egress_telemetry_ref)
+    egress_telemetry_ref = Process.send_after(self(), :send_egress_telemetry, egress_telemetry_interval_in_ms)
+    {:noreply, %{state | egress_telemetry_ref: egress_telemetry_ref}}
   end
 
   defp chunked_killing(cont \\ nil) do
@@ -84,5 +133,38 @@ defmodule RealtimeWeb.RealtimeChannel.Tracker do
     end
   end
 
+  defp collect_egress_telemetry(pid_and_port_list, cont \\ nil, acc \\ %{}) do
+    result = if cont, do: :ets.select(cont), else: :ets.select(@table, @egress_telemetry_match, 1000)
+
+    case result do
+      :"$end_of_table" ->
+        acc
+
+      {pids, cont} ->
+        acc =
+          Enum.reduce(pids, acc, fn [pid, tenant_external_id], acc ->
+            ports = Map.get(pid_and_port_list, pid, [])
+
+            output_bytes =
+              Enum.sum_by(ports, fn port ->
+                case :inet.getstat(port, [:send_oct]) do
+                  {:ok, stats} -> stats[:send_oct]
+                  _ -> 0
+                end
+              end)
+
+            {_, acc} =
+              Map.get_and_update(acc, tenant_external_id, fn
+                nil -> {output_bytes, output_bytes}
+                output_bytes -> {output_bytes, output_bytes + output_bytes}
+              end)
+
+            acc
+          end)
+
+        collect_egress_telemetry(pid_and_port_list, cont, acc)
+    end
+  end
+
   def table_name, do: @table
 end

mix.exs

@@ -4,7 +4,7 @@ defmodule Realtime.MixProject do
   def project do
     [
       app: :realtime,
-      version: "2.61.0",
+      version: "2.61.2",
       elixir: "~> 1.18",
       elixirc_paths: elixirc_paths(Mix.env()),
       start_permanent: Mix.env() == :prod,

test/realtime/monitoring/prom_ex/plugins/tenant_test.exs

@@ -63,6 +63,14 @@ defmodule Realtime.PromEx.Plugins.TenantTest do
                     %{tenant: external_id}
                   )
                 end
+
+                def fake_output_bytes(external_id) do
+                  Realtime.Telemetry.execute(
+                    [:realtime, :connections, :output_bytes],
+                    %{output_bytes: 100},
+                    %{tenant: external_id}
+                  )
+                end
               end
             end)
 
@@ -316,6 +324,16 @@ defmodule Realtime.PromEx.Plugins.TenantTest do
 
       assert metric_value(bucket_pattern) > 0
     end
+
+    test "egress bytes metric exists after check", context do
+      external_id = context.tenant.external_id
+      pattern = ~r/realtime_connections_output_bytes{tenant="#{external_id}"}\s(?<number>\d+)/
+
+      FakeUserCounter.fake_output_bytes(external_id)
+
+      Process.sleep(200)
+      assert metric_value(pattern) == 100
+    end
   end
 
   defp metric_value(pattern) do