Switch to PromEx for prometheus metrics

Recommending use of the separate HTTP server for exposing the metrics
and securing it externally on your firewall or reverse proxy. It will
listen on port 4021 by default.

lib/pleroma/prom_ex.ex

@@ -0,0 +1,49 @@
+defmodule Pleroma.PromEx do
+  use PromEx, otp_app: :pleroma
+
+  alias PromEx.Plugins
+
+  @impl true
+  def plugins do
+    [
+      # PromEx built in plugins
+      Plugins.Application,
+      Plugins.Beam,
+      {Plugins.Phoenix, router: Pleroma.Web.Router, endpoint: Pleroma.Web.Endpoint},
+      Plugins.Ecto,
+      Plugins.Oban
+      # Plugins.PhoenixLiveView,
+      # Plugins.Absinthe,
+      # Plugins.Broadway,
+
+      # Add your own PromEx metrics plugins
+      # Pleroma.Users.PromExPlugin
+    ]
+  end
+
+  @impl true
+  def dashboard_assigns do
+    [
+      datasource_id: Pleroma.Config.get([Pleroma.PromEx, :datasource]),
+      default_selected_interval: "30s"
+    ]
+  end
+
+  @impl true
+  def dashboards do
+    [
+      # PromEx built in Grafana dashboards
+      {:prom_ex, "application.json"},
+      {:prom_ex, "beam.json"},
+      {:prom_ex, "phoenix.json"},
+      {:prom_ex, "ecto.json"},
+      {:prom_ex, "oban.json"}
+      # {:prom_ex, "phoenix_live_view.json"},
+      # {:prom_ex, "absinthe.json"},
+      # {:prom_ex, "broadway.json"},
+
+      # Add your dashboard definitions here with the format: {:otp_app, "path_in_priv"}
+      # {:pleroma, "/grafana_dashboards/user_metrics.json"}
+    ]
+  end
+end