defmodule HistoryWeb.Telemetry do
use Supervisor
import Telemetry.Metrics
def start_link(arg) do
Supervisor.start_link(__MODULE__, arg, name: __MODULE__)
end
@impl true
def init(_arg) do
children = [
{TelemetryMetricsPrometheus,
[
metrics: metrics(),
port: prometheus_metrics_port(),
name: prometheus_metrics_name(),
options: [ref: :"TelemetryMetricsPrometheus.Router.HTTP_#{prometheus_metrics_port()}"]
]}
]
Supervisor.init(children, strategy: :one_for_one)
end
def metrics do
[
# Phoenix Metrics
last_value("phoenix.endpoint.stop.duration",
tags: [:method, :request_path],
tag_values: &tag_method_and_request_path/1,
unit: {:native, :millisecond}
),
last_value("phoenix.router_dispatch.stop.duration",
tags: [:controller_action],
tag_values: &tag_controller_action/1,
unit: {:native, :millisecond}
),
# Database Metrics
last_value("history.repo.query.total_time", unit: {:native, :millisecond}),
last_value("history.repo.query.decode_time", unit: {:native, :millisecond}),
last_value("history.repo.query.query_time", unit: {:native, :millisecond}),
last_value("history.repo.query.queue_time", unit: {:native, :millisecond}),
last_value("history.repo.query.idle_time", unit: {:native, :millisecond}),
# Broadway Metrics
last_value("broadway.processor.message.stop.duration",
tags: [:name, :index],
unit: {:native, :millisecond}
),
# TODO: Figure out how to get last value + counter. Currently can only be one or the other
# counter("broadway.processor.message.stop.duration",
# tags: [:name, :index],
# unit: {:native, :millisecond}
# ),
counter("broadway.processor.message.exception.duration",
tags: [:name, :index],
unit: {:native, :millisecond}
),
]
end
defp prometheus_metrics_name do
Application.get_env(:history, :prometheus_metrics_name, :history_prometheus_metrics)
end
defp prometheus_metrics_port do
Application.get_env(:history, :prometheus_metrics_port, 9569)
end
# Extracts labels like "GET /"
defp tag_method_and_request_path(metadata) do
Map.take(metadata.conn, [:method, :request_path])
end
# Extracts controller#action from route dispatch
defp tag_controller_action(%{plug: plug, plug_opts: plug_opts}) when is_atom(plug_opts) do
%{controller_action: "#{inspect(plug)}##{plug_opts}"}
end
defp tag_controller_action(%{plug: plug}) do
%{controller_action: inspect(plug)}
end
end