Harlock.Telemetry (harlock v0.4.0)

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Telemetry events emitted by the Harlock runtime.

Attach handlers in your app's startup (Application.start/2) or in tests:

:telemetry.attach(
  "log-frame-duration",
  [:harlock, :frame, :render, :stop],
  fn _event, %{duration: duration}, _meta, _ ->
    IO.puts("frame: #{System.convert_time_unit(duration, :native, :microsecond)}µs")
  end,
  nil
)

All durations come from :telemetry.span/3 (:native time units — use System.convert_time_unit/3 to format).

Events

[:harlock, :frame, :render, :start] / [..., :stop] / [..., :exception]

Wraps view/1 + tree traversal + diff emission for one frame.

  • measurements (on :stop): %{duration: native, monotonic_time: native}
  • metadata (on :stop): %{app: module, dirty: boolean, rows: integer, cols: integer}

[:harlock, :input, :dispatch, :start] / [..., :stop] / [..., :exception]

Wraps the path from event arrival in the runtime mailbox to the return of update/2. Catches keystroke-to-model lag.

  • measurements (on :stop): %{duration: native, monotonic_time: native}
  • metadata (on :stop): %{app: module, event: term, focused: term}

[:harlock, :cmd, :dispatch]

Emitted when a Cmd is handed to the task supervisor.

  • measurements: %{count: 1}

  • metadata: %{kind: :fun | :batch | :map | :none}

[:harlock, :cmd, :complete]

Emitted when a Cmd task returns (success or {:cmd_error, _}).

  • measurements: %{duration: native}

  • metadata: %{status: :ok | :error}

[:harlock, :reader, :tty_lost]

One-shot when the input reader sees EOF on /dev/tty (ssh disconnect, terminal close, etc.). Useful for an oncall alert.

  • measurements: %{count: 1}

  • metadata: %{reason: :eof | term}