Crude logging of telemetry events for load testing

CHANGELOG.md

@@ -14,6 +14,8 @@ and this project adheres to
   OS information [#1170](https://github.com/OpenFn/Lightning/issues/1170)
 - Expose additional metrics to LiveDashboard
   [#1171](https://github.com/OpenFn/Lightning/issues/1171)
+- Add plumbing to dump Lightning metrics during load testing
+  [#1178](https://github.com/OpenFn/Lightning/issues/1178)
 
 ### Changed
 

benchmarking/BENCHMARKING.md

@@ -6,28 +6,47 @@ Execute the following steps to run a benchmark on Lightning:
    installed locally. If you're using `asdf` you can run `asdf install` in the
    project root.
 
-2. Spin up your Lightning local instance
+2. Start up a local Lightning instance with an attached iex session:
+
+    `iex -S mix phx.server`
 
-3. Run the demo setup script: `mix run --no-start priv/repo/demo.exs` The
+3. In the attached iex session, run the following, to have Lightning log internal telemetry data:
+
+    ```elixir
+      filepath = Path.join("benchmarking", "load_test_data.csv")
+      output_file = File.open!(filepath, [:append])
+
+      c "benchmarking/load_test_production_spans.exs"
+
+      LoadTestingPrep.init(output_file)
+    ```
+
+4. Run the demo setup script: `mix run --no-start priv/repo/demo.exs` The
    `webhookURL` is already set to default to the webhook created in the demo
    data
 
-4. In another terminal (do not stop the Lightning server) run the
+5. In another terminal (do not stop the Lightning server) run the
    `benchmarking/script.js` file using the following command
 
-```bash
-k6 run benchmarking/script.js
-```
+    ```bash
+    k6 run benchmarking/script.js
+    ```
+
+    If the script exits successfully, this means the app met the defined performance
+    thresholds.
+
+    To collect the benchmarking data in a CSV file, run the previous command with
+    the `--out filename` option.
 
-If the script exits successfully, this means the app met the defined performance
-thresholds.
+    ```bash
+    k6 run --out csv=test_results.csv benchmarking/script.js
+    ```
 
-To collect the benchmarking data in a CSV file, run the previous command with
-the `--out filename` option.
+6. In the iex session, close the output file:
 
-```bash
-k6 run --out csv=test_results.csv benchmarking/script.js
-```
+    ```elixir
+    LoadTestingPrep.fin(output_file)
+    ```
 
 See [results output](https://k6.io/docs/get-started/results-output/) for other
 available output formats.

benchmarking/load_test_production_spans.exs

@@ -0,0 +1,54 @@
+defmodule TelemetryCSVLogger do
+  require Logger
+
+  def handle_event(
+        [:lightning, :workorder, :webhook, :stop] = event,
+        %{duration: duration} = measurements,
+        _metadata,
+        output_file: file
+      ) do
+    log_received(event, measurements)
+
+    IO.binwrite(file, "lightning.create_webhook_workorder.stop, #{duration}\n")
+  end
+
+  def handle_event(event, _measurements, _metadata, _config) do
+    log_received(event)
+  end
+
+  defp native_to_microsecond(duration) do
+    System.convert_time_unit(duration, :native, :microsecond)
+  end
+
+  defp log_received(event, %{duration: duration}) do
+    duration = native_to_microsecond(duration)
+
+    Logger.info(
+      "Received #{event |> Enum.join(".")} event. Duration: #{duration}µs"
+    )
+  end
+
+  defp log_received(event) do
+    Logger.info("Received #{event |> Enum.join(".")} event.")
+  end
+end
+
+defmodule LoadTestingPrep do
+  def init(output_file) do
+    telemetry_events = [
+      [:lightning, :workorder, :webhook, :stop],
+    ]
+
+    :ok =
+      :telemetry.attach_many(
+        "lightning-load-testing-events",
+        telemetry_events,
+        &TelemetryCSVLogger.handle_event/4,
+        output_file: output_file
+      )
+  end
+
+  def fin(file) do
+    File.close(file)
+  end
+end