Remove Prometheus-based metrics

Never use them

fly.toml

@@ -40,7 +40,3 @@ soft_limit = 1000
 memory = '512mb'
 cpu_kind = 'shared'
 cpus = 1
-
-[metrics]
-path = "/metrics"
-port = 8080

lib/music_library_web/endpoint.ex

@@ -15,8 +15,6 @@ defmodule MusicLibraryWeb.Endpoint do
     encrypt: true
   ]
 
-  plug MusicLibraryWeb.Telemetry.Plug, at: "/metrics"
-
   socket "/live", Phoenix.LiveView.Socket,
     websocket: [connect_info: [session: @session_options]],
     longpoll: [connect_info: [session: @session_options]]

lib/music_library_web/telemetry.ex

@@ -10,7 +10,6 @@ defmodule MusicLibraryWeb.Telemetry do
   def init(_arg) do
     children = [
       {MusicLibraryWeb.Telemetry.Storage, metrics()},
-      {TelemetryMetricsPrometheus.Core, [metrics: prometheus_metrics()]},
       # Telemetry poller will execute the given period measurements
       # every 10_000ms. Learn more here: https://hexdocs.pm/telemetry_metrics
       {:telemetry_poller, measurements: periodic_measurements(), period: 10_000}
@@ -104,39 +103,6 @@ defmodule MusicLibraryWeb.Telemetry do
     ]
   end
 
-  def prometheus_metrics do
-    [
-      # VM Metrics
-      last_value("vm.memory.total", unit: {:byte, :megabyte}),
-      last_value("vm.total_run_queue_lengths.total"),
-      last_value("vm.total_run_queue_lengths.cpu"),
-      last_value("vm.total_run_queue_lengths.io"),
-
-      # Database Metrics
-      last_value("music_library.repo.query.total_time",
-        unit: {:native, :millisecond},
-        description: "The sum of the other measurements"
-      ),
-      last_value("music_library.repo.query.decode_time",
-        unit: {:native, :millisecond},
-        description: "The time spent decoding the data received from the database"
-      ),
-      last_value("music_library.repo.query.query_time",
-        unit: {:native, :millisecond},
-        description: "The time spent executing the query"
-      ),
-      last_value("music_library.repo.query.queue_time",
-        unit: {:native, :millisecond},
-        description: "The time spent waiting for a database connection"
-      ),
-      last_value("music_library.repo.query.idle_time",
-        unit: {:native, :millisecond},
-        description:
-          "The time the connection spent waiting before being checked out for the query"
-      )
-    ]
-  end
-
   defp periodic_measurements do
     [
       # A module, function and arguments to be invoked periodically.

lib/music_library_web/telemetry/plug.ex

@@ -1,22 +0,0 @@
-defmodule MusicLibraryWeb.Telemetry.Plug do
-  @behaviour Plug
-
-  import Plug.Conn
-
-  def init(opts) do
-    Keyword.validate!(opts, [:at])
-  end
-
-  def call(conn, opts) do
-    at = Keyword.fetch!(opts, :at)
-
-    if conn.request_path == at do
-      conn
-      |> put_resp_content_type("text/plain")
-      |> send_resp(200, TelemetryMetricsPrometheus.Core.scrape())
-      |> halt()
-    else
-      conn
-    end
-  end
-end

mix.exs

@@ -101,7 +101,6 @@ defmodule MusicLibrary.MixProject do
 
       # Prod error/perf tooling
       {:phoenix_live_dashboard, "~> 0.8.3"},
-      {:telemetry_metrics_prometheus_core, "~> 1.2"},
       {:error_tracker, "~> 0.6.0"},
       {:recon, "~> 2.5"},
       {:telemetry_metrics, "~> 1.0"},

mix.lock

@@ -55,7 +55,6 @@
   "tailwind": {:hex, :tailwind, "0.3.1", "a89d2835c580748c7a975ad7dd3f2ea5e63216dc16d44f9df492fbd12c094bed", [:mix], [], "hexpm", "98a45febdf4a87bc26682e1171acdedd6317d0919953c353fcd1b4f9f4b676a2"},
   "telemetry": {:hex, :telemetry, "1.3.0", "fedebbae410d715cf8e7062c96a1ef32ec22e764197f70cda73d82778d61e7a2", [:rebar3], [], "hexpm", "7015fc8919dbe63764f4b4b87a95b7c0996bd539e0d499be6ec9d7f3875b79e6"},
   "telemetry_metrics": {:hex, :telemetry_metrics, "1.1.0", "5bd5f3b5637e0abea0426b947e3ce5dd304f8b3bc6617039e2b5a008adc02f8f", [:mix], [{:telemetry, "~> 0.4 or ~> 1.0", [hex: :telemetry, repo: "hexpm", optional: false]}], "hexpm", "e7b79e8ddfde70adb6db8a6623d1778ec66401f366e9a8f5dd0955c56bc8ce67"},
-  "telemetry_metrics_prometheus_core": {:hex, :telemetry_metrics_prometheus_core, "1.2.1", "c9755987d7b959b557084e6990990cb96a50d6482c683fb9622a63837f3cd3d8", [:mix], [{:telemetry, "~> 0.4 or ~> 1.0", [hex: :telemetry, repo: "hexpm", optional: false]}, {:telemetry_metrics, "~> 0.6 or ~> 1.0", [hex: :telemetry_metrics, repo: "hexpm", optional: false]}], "hexpm", "5e2c599da4983c4f88a33e9571f1458bf98b0cf6ba930f1dc3a6e8cf45d5afb6"},
   "telemetry_poller": {:hex, :telemetry_poller, "1.2.0", "ba82e333215aed9dd2096f93bd1d13ae89d249f82760fcada0850ba33bac154b", [:rebar3], [{:telemetry, "~> 1.0", [hex: :telemetry, repo: "hexpm", optional: false]}], "hexpm", "7216e21a6c326eb9aa44328028c34e9fd348fb53667ca837be59d0aa2a0156e8"},
   "thousand_island": {:hex, :thousand_island, "1.3.13", "d598c609172275f7b1648c9f6eddf900e42312b09bfc2f2020358f926ee00d39", [:mix], [{:telemetry, "~> 0.4 or ~> 1.0", [hex: :telemetry, repo: "hexpm", optional: false]}], "hexpm", "5a34bdf24ae2f965ddf7ba1a416f3111cfe7df50de8d66f6310e01fc2e80b02a"},
   "tidewave": {:hex, :tidewave, "0.1.6", "f07514ee2c348c2e682a2632309ac6d8ec425392bfb803955a6bb19ca5508e2f", [:mix], [{:circular_buffer, "~> 0.4", [hex: :circular_buffer, repo: "hexpm", optional: false]}, {:igniter, ">= 0.5.47 and < 1.0.0-0", [hex: :igniter, repo: "hexpm", optional: true]}, {:jason, "~> 1.4", [hex: :jason, repo: "hexpm", optional: false]}, {:plug, "~> 1.17", [hex: :plug, repo: "hexpm", optional: false]}, {:req, "~> 0.5", [hex: :req, repo: "hexpm", optional: false]}], "hexpm", "3708592f325e1f54b99b215cd8c38f726732451bf5cfa16d73584793f99d9da4"},