init: inital commit

lib/localiser/mqtt/telemetry.ex

@@ -0,0 +1,59 @@
+defmodule Localiser.MQTT.Telemetry do
+  @moduledoc """
+  GenServer responsible for tracking telemetry data related to MQTT messages.
+  """
+
+  use GenServer
+  require Logger
+
+  def start_link(opts) do
+    GenServer.start_link(__MODULE__, opts, name: __MODULE__)
+  end
+
+  def count_reading() do
+    GenServer.cast(__MODULE__, :count_reading)
+  end
+
+  def count_error() do
+    GenServer.cast(__MODULE__, :count_error)
+  end
+
+  @log_interval 60_000
+
+  # GenServer Callbacks
+
+  @impl true
+  def init(_opts) do
+    schedule_log()
+    {:ok, %{total_readings: 0, total_errors: 0}}
+  end
+
+  @impl true
+  def handle_cast(:count_reading, state) do
+    new_count = state.total_readings + 1
+    {:noreply, %{state | total_readings: new_count}}
+  end
+
+  @impl true
+  def handle_cast(:count_error, state) do
+    new_count = state.total_errors + 1
+    {:noreply, %{state | total_errors: new_count}}
+  end
+
+  @impl true
+  def handle_info(:log_stats, state) do
+    rate = if state.total_readings > 0 do
+      Float.round(state.total_errors / state.total_readings * 100, 2)
+    else
+      0.0
+    end
+    Logger.info("[MQTT.Telemetry] #{state.total_readings} readings, #{state.total_errors} errors (#{rate} err rate) in last #{@log_interval / 1000}s.")
+    schedule_log()
+    {:noreply, state}
+  end
+
+  # Private helper functions
+  defp schedule_log() do
+    Process.send_after(self(), :log_stats, @log_interval)
+  end
+end