[Enhancement] Add Prometheus support (#556)

* Added prometheus to deps list

* WIP - screwing around with Prometheus and grafana

* Added basic prometheus config

* Updated docs in prom_ex module

* Updated README

README.md

@@ -142,18 +142,19 @@ If you change this setting and it works well for you, please leave a comment on
 
 ### Environment variables
 
-| Name                        | Required? | Default                   | Notes                                                                                                                           |
-| --------------------------- | --------- | ------------------------- | ------------------------------------------------------------------------------------------------------------------------------- |
-| `TZ`                        | No        | `UTC`                     | Must follow IANA TZ format                                                                                                      |
-| `LOG_LEVEL`                 | No        | `debug`                   | Can be set to `info` but `debug` is strongly recommended                                                                        |
-| `BASIC_AUTH_USERNAME`       | No        |                           | See [authentication docs](https://github.com/kieraneglin/pinchflat/wiki/Username-and-Password)                                  |
-| `BASIC_AUTH_PASSWORD`       | No        |                           | See [authentication docs](https://github.com/kieraneglin/pinchflat/wiki/Username-and-Password)                                  |
-| `EXPOSE_FEED_ENDPOINTS`     | No        | `false`                   | See [RSS feed docs](https://github.com/kieraneglin/pinchflat/wiki/Podcast-RSS-Feeds)                                            |
-| `ENABLE_IPV6`               | No        | `false`                   | Setting to _any_ non-blank value will enable IPv6                                                                               |
-| `JOURNAL_MODE`              | No        | `wal`                     | Set to `delete` if your config directory is stored on a network share (not recommended)                                         |
-| `TZ_DATA_DIR`               | No        | `/etc/elixir_tzdata_data` | The container path where the timezone database is stored                                                                        |
-| `BASE_ROUTE_PATH`           | No        | `/`                       | The base path for route generation. Useful when running behind certain reverse proxies, but prefix must be stripped.            |
-| `YT_DLP_WORKER_CONCURRENCY` | No        | `2`                       | The number of concurrent workers that use `yt-dlp` _per queue_. Set to 1 if you're getting IP limited, otherwise don't touch it |
+| Name                        | Required? | Default                   | Notes                                                                                                                                     |
+| --------------------------- | --------- | ------------------------- | ----------------------------------------------------------------------------------------------------------------------------------------- |
+| `TZ`                        | No        | `UTC`                     | Must follow IANA TZ format                                                                                                                |
+| `LOG_LEVEL`                 | No        | `debug`                   | Can be set to `info` but `debug` is strongly recommended                                                                                  |
+| `BASIC_AUTH_USERNAME`       | No        |                           | See [authentication docs](https://github.com/kieraneglin/pinchflat/wiki/Username-and-Password)                                            |
+| `BASIC_AUTH_PASSWORD`       | No        |                           | See [authentication docs](https://github.com/kieraneglin/pinchflat/wiki/Username-and-Password)                                            |
+| `EXPOSE_FEED_ENDPOINTS`     | No        | `false`                   | See [RSS feed docs](https://github.com/kieraneglin/pinchflat/wiki/Podcast-RSS-Feeds)                                                      |
+| `ENABLE_IPV6`               | No        | `false`                   | Setting to _any_ non-blank value will enable IPv6                                                                                         |
+| `JOURNAL_MODE`              | No        | `wal`                     | Set to `delete` if your config directory is stored on a network share (not recommended)                                                   |
+| `TZ_DATA_DIR`               | No        | `/etc/elixir_tzdata_data` | The container path where the timezone database is stored                                                                                  |
+| `BASE_ROUTE_PATH`           | No        | `/`                       | The base path for route generation. Useful when running behind certain reverse proxies - prefixes must be stripped.                       |
+| `YT_DLP_WORKER_CONCURRENCY` | No        | `2`                       | The number of concurrent workers that use `yt-dlp` _per queue_. Set to 1 if you're getting IP limited, otherwise don't touch it           |
+| `ENABLE_PROMETHEUS`         | No        | `false`                   | Setting to _any_ non-blank value will enable Prometheus. See [docs](https://github.com/kieraneglin/pinchflat/wiki/Prometheus-and-Grafana) |
 
 ## EFF donations
 

config/config.exs

@@ -99,6 +99,12 @@ config :logger, :default_formatter,
 # Use Jason for JSON parsing in Phoenix
 config :phoenix, :json_library, Jason
 
+config :pinchflat, Pinchflat.PromEx,
+  disabled: true,
+  manual_metrics_start_delay: :no_delay,
+  drop_metrics_groups: [],
+  metrics_server: :disabled
+
 # Import environment specific config. This must remain at the bottom
 # of this file so it overrides the configuration defined above.
 import_config "#{config_env()}.exs"

config/dev.exs

@@ -81,3 +81,5 @@ config :phoenix_live_view, :debug_heex_annotations, true
 
 # Disable swoosh api client as it is only required for production adapters.
 config :swoosh, :api_client, false
+
+config :pinchflat, Pinchflat.PromEx, disabled: false

config/runtime.exs

@@ -72,6 +72,7 @@ if config_env() == :prod do
   # For running PF in a subdirectory via a reverse proxy
   base_route_path = System.get_env("BASE_ROUTE_PATH", "/")
   enable_ipv6 = String.length(System.get_env("ENABLE_IPV6", "")) > 0
+  enable_prometheus = String.length(System.get_env("ENABLE_PROMETHEUS", "")) > 0
 
   config :logger, level: String.to_existing_atom(System.get_env("LOG_LEVEL", "debug"))
 
@@ -95,6 +96,8 @@ if config_env() == :prod do
     database: db_path,
     journal_mode: journal_mode
 
+  config :pinchflat, Pinchflat.PromEx, disabled: !enable_prometheus
+
   # The secret key base is used to sign/encrypt cookies and other secrets.
   # A default value is used in config/dev.exs and config/test.exs but you
   # want to use a different value for prod and you most likely don't want

lib/pinchflat/application.ex

@@ -11,6 +11,7 @@ defmodule Pinchflat.Application do
     check_and_update_timezone()
 
     children = [
+      Pinchflat.PromEx,
       PinchflatWeb.Telemetry,
       Pinchflat.Repo,
       # Must be before startup tasks

lib/pinchflat/prom_ex.ex

@@ -0,0 +1,40 @@
+defmodule Pinchflat.PromEx do
+  @moduledoc """
+  Configuration for the PromEx library which provides Prometheus metrics
+  """
+
+  use PromEx, otp_app: :pinchflat
+
+  alias PromEx.Plugins
+
+  @impl true
+  def plugins do
+    [
+      Plugins.Application,
+      Plugins.Beam,
+      {Plugins.Phoenix, router: PinchflatWeb.Router, endpoint: PinchflatWeb.Endpoint},
+      Plugins.Ecto,
+      Plugins.Oban,
+      Plugins.PhoenixLiveView
+    ]
+  end
+
+  @impl true
+  def dashboard_assigns do
+    [
+      default_selected_interval: "30s"
+    ]
+  end
+
+  @impl true
+  def dashboards do
+    [
+      {: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"}
+    ]
+  end
+end

lib/pinchflat_web/endpoint.ex

@@ -32,6 +32,8 @@ defmodule PinchflatWeb.Endpoint do
     plug Phoenix.Ecto.CheckRepoStatus, otp_app: :pinchflat
   end
 
+  plug PromEx.Plug, prom_ex_module: Pinchflat.PromEx
+
   plug Phoenix.LiveDashboard.RequestLogger,
     param_key: "request_logger",
     cookie_key: "request_logger"

mix.exs

@@ -60,16 +60,17 @@ defmodule Pinchflat.MixProject do
       {:esbuild, "~> 0.8", runtime: Mix.env() == :dev},
       {:tailwind, "~> 0.2.0", runtime: Mix.env() == :dev},
       {:swoosh, "~> 1.3"},
-      {:finch, "~> 0.13"},
-      {:telemetry_metrics, "~> 0.6"},
-      {:telemetry_poller, "~> 1.0"},
+      {:finch, "~> 0.18"},
+      {:telemetry_metrics, "~> 1.0"},
+      {:telemetry_poller, "~> 1.1"},
       {:gettext, "~> 0.20"},
       {:jason, "~> 1.2"},
       {:dns_cluster, "~> 0.1.1"},
       {:plug_cowboy, "~> 2.5"},
       {:oban, "~> 2.17"},
       {:nimble_parsec, "~> 1.4"},
       {:timex, "~> 3.0"},
+      {:prom_ex, "~> 1.11.0"},
       {:mox, "~> 1.0", only: :test},
       {:credo, "~> 1.7.7", only: [:dev, :test], runtime: false},
       {:credo_naming, "~> 2.1", only: [:dev, :test], runtime: false},