distraction.party/lib/pleroma/prometheus_exporter.ex

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defmodule Pleroma.PrometheusExporter do
@moduledoc """
Exports metrics in Prometheus format.
Mostly exists because of https://github.com/beam-telemetry/telemetry_metrics_prometheus_core/issues/52
Basically we need to fetch metrics every so often, or the lib will let them pile up and eventually crash the VM.
It also sorta acts as a cache so there is that too.
"""
use GenServer
require Logger
def start_link(_opts) do
GenServer.start_link(__MODULE__, :ok, name: __MODULE__)
end
def init(_opts) do
schedule_next()
{:ok, ""}
end
defp schedule_next do
Process.send_after(self(), :gather, 60_000)
end
# Scheduled function, gather metrics and schedule next run
def handle_info(:gather, _state) do
schedule_next()
state = TelemetryMetricsPrometheus.Core.scrape()
{:noreply, state}
end
# Trigger the call dynamically, mostly for testing
def handle_call(:gather, _from, _state) do
state = TelemetryMetricsPrometheus.Core.scrape()
{:reply, state, state}
end
def handle_call(:show, _from, state) do
{:reply, state, state}
end
def show do
GenServer.call(__MODULE__, :show)
end
def gather do
GenServer.call(__MODULE__, :gather)
end
end