Add spans for phoenix controller view rendering (#531)

Author: binaryseed

examples/apps/phx_example/test/phx_example_test.exs

@@ -90,9 +90,11 @@ defmodule PhxExampleTest do
         tx_span = TestHelper.find_event(span_events, "/Phoenix/PhxExampleWeb.HomeLive/index")
         process_span = TestHelper.find_event(span_events, "Transaction Root Process")
         mount_span = TestHelper.find_event(span_events, "PhxExampleWeb.HomeLive:index.mount")
+        render_span = TestHelper.find_event(span_events, "PhxExampleWeb.Layouts.show")
 
         assert process_span[:parentId] == tx_span[:guid]
         assert mount_span[:"live_view.params"]
+        assert render_span[:"phoenix.view"]
       end
 
       @endpoint PhxExampleWeb.Endpoint

lib/new_relic/telemetry/phoenix.ex

@@ -1,6 +1,8 @@
 defmodule NewRelic.Telemetry.Phoenix do
   use GenServer
 
+  alias NewRelic.Tracer
+
   @moduledoc """
   Provides `Phoenix` instrumentation via `telemetry`.
 
@@ -20,10 +22,14 @@ defmodule NewRelic.Telemetry.Phoenix do
   end
 
   @phoenix_router_start [:phoenix, :router_dispatch, :start]
+  @phoenix_controller_render_start [:phoenix, :controller, :render, :start]
+  @phoenix_controller_render_stop [:phoenix, :controller, :render, :stop]
   @phoenix_error [:phoenix, :error_rendered]
 
   @phoenix_events [
     @phoenix_router_start,
+    @phoenix_controller_render_start,
+    @phoenix_controller_render_stop,
     @phoenix_error
   ]
 
@@ -83,6 +89,33 @@ defmodule NewRelic.Telemetry.Phoenix do
     |> NewRelic.add_attributes()
   end
 
+  def handle_event(
+        @phoenix_controller_render_start,
+        meas,
+        %{view: view, template: template, format: format} = meta,
+        _config
+      ) do
+    Tracer.Direct.start_span(
+      meta.telemetry_span_context,
+      "#{inspect(view)}.show",
+      system_time: meas.system_time,
+      attributes: [
+        "phoenix.view": inspect(view),
+        "phoenix.template": template,
+        "phoenix.format": format
+      ]
+    )
+  end
+
+  def handle_event(
+        @phoenix_controller_render_stop,
+        meas,
+        meta,
+        _config
+      ) do
+    Tracer.Direct.stop_span(meta.telemetry_span_context, duration: meas.duration)
+  end
+
   def handle_event(_event, _measurements, _meta, _config) do
     :ignore
   end