Properly format HTTP request latency for GCL

Author: AndrewDryga

lib/logger_json/formatters/google_cloud.ex

@@ -226,13 +226,14 @@ defmodule LoggerJSON.Formatters.GoogleCloud do
   defp format_crash_report_location(_meta), do: nil
 
   if Code.ensure_loaded?(Plug.Conn) do
-    defp format_http_request(%{conn: %Plug.Conn{} = conn}) do
+    defp format_http_request(%{conn: %Plug.Conn{} = conn} = assigns) do
       request_method = conn.method |> to_string() |> String.upcase()
       request_url = Plug.Conn.request_url(conn)
       status = conn.status
       user_agent = LoggerJSON.Formatter.Plug.get_header(conn, "user-agent")
       remote_ip = LoggerJSON.Formatter.Plug.remote_ip(conn)
       referer = LoggerJSON.Formatter.Plug.get_header(conn, "referer")
+      latency = http_request_latency(assigns)
 
       json_map(
         protocol: Plug.Conn.get_http_protocol(conn),
@@ -241,13 +242,23 @@ defmodule LoggerJSON.Formatters.GoogleCloud do
         status: status,
         userAgent: user_agent,
         remoteIp: remote_ip,
-        referer: referer
+        referer: referer,
+        latency: latency
       )
     end
   end
 
   defp format_http_request(_meta), do: nil
 
+  defp http_request_latency(%{duration_us: duration_us}) do
+    duration_s = Float.round(duration_us / 1_000_000, 9)
+    "#{duration_s}s"
+  end
+
+  defp http_request_latency(_assigns) do
+    nil
+  end
+
   defp format_affected_user(%{user_id: user_id}), do: "user:" <> user_id
   defp format_affected_user(%{identity_id: identity_id}), do: "identity:" <> identity_id
   defp format_affected_user(%{actor_id: actor_id}), do: "actor:" <> actor_id

test/logger_json/formatters/google_cloud_test.exs

@@ -331,7 +331,7 @@ defmodule LoggerJSON.Formatters.GoogleCloudTest do
 
     log_entry =
       capture_log(fn ->
-        Logger.debug("Hello")
+        Logger.debug("Hello", duration_us: 123_456)
       end)
       |> decode_or_print_error()
 
@@ -342,7 +342,8 @@ defmodule LoggerJSON.Formatters.GoogleCloudTest do
              "requestMethod" => "GET",
              "requestUrl" => "http://www.example.com/",
              "status" => 200,
-             "userAgent" => "Mozilla/5.0"
+             "userAgent" => "Mozilla/5.0",
+             "latency" => "0.123456s"
            }
   end
 
@@ -369,7 +370,8 @@ defmodule LoggerJSON.Formatters.GoogleCloudTest do
              "requestMethod" => "PATCH",
              "requestUrl" => "http://www.example.com/",
              "status" => 503,
-             "userAgent" => "Mozilla/5.0"
+             "userAgent" => "Mozilla/5.0",
+             "latency" => nil
            }
   end