WIP - screwing around with Prometheus and grafana

config/config.exs

@@ -99,6 +99,20 @@ config :logger, :default_formatter,
 # Use Jason for JSON parsing in Phoenix
 config :phoenix, :json_library, Jason
 
+config :pinchflat, Pinchflat.PromEx,
+  disabled: false,
+  manual_metrics_start_delay: :no_delay,
+  drop_metrics_groups: [],
+  metrics_server: :disabled,
+  grafana: [
+    host: System.get_env("GRAFANA_CLOUD_URL", "http://192.168.1.170:3033"),
+    username: System.get_env("GRAFANA_USERNAME", "admin"),
+    password: System.get_env("GRAFANA_PASSWORD", "admin"),
+    # This is an optional setting and will default to `true`
+    folder_name: "zero-to-graphql-using-elixir",
+    upload_dashboards_on_start: true
+  ]
+
 # 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"

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 +1,90 @@
+defmodule Pinchflat.PromEx do
+  @moduledoc """
+  Be sure to add the following to finish setting up PromEx:
+
+  1. Update your configuration (config.exs, dev.exs, prod.exs, releases.exs, etc) to
+     configure the necessary bit of PromEx. Be sure to check out `PromEx.Config` for
+     more details regarding configuring PromEx:
+     ```
+     config :pinchflat, Pinchflat.PromEx,
+       disabled: false,
+       manual_metrics_start_delay: :no_delay,
+       drop_metrics_groups: [],
+       grafana: :disabled,
+       metrics_server: :disabled
+     ```
+
+  2. Add this module to your application supervision tree. It should be one of the first
+     things that is started so that no Telemetry events are missed. For example, if PromEx
+     is started after your Repo module, you will miss Ecto's init events and the dashboards
+     will be missing some data points:
+     ```
+     def start(_type, _args) do
+       children = [
+         Pinchflat.PromEx,
+
+         ...
+       ]
+
+       ...
+     end
+     ```
+
+  3. Update your `endpoint.ex` file to expose your metrics (or configure a standalone
+     server using the `:metrics_server` config options). Be sure to put this plug before
+     your `Plug.Telemetry` entry so that you can avoid having calls to your `/metrics`
+     endpoint create their own metrics and logs which can pollute your logs/metrics given
+     that Prometheus will scrape at a regular interval and that can get noisy:
+     ```
+     defmodule PinchflatWeb.Endpoint do
+       use Phoenix.Endpoint, otp_app: :pinchflat
+
+       ...
+
+       plug PromEx.Plug, prom_ex_module: Pinchflat.PromEx
+
+       ...
+     end
+     ```
+
+  4. Update the list of plugins in the `plugins/0` function return list to reflect your
+     application's dependencies. Also update the list of dashboards that are to be uploaded
+     to Grafana in the `dashboards/0` function.
+  """
+
+  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
+    [
+      datasource_id: "prometheus",
+      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"