Provide metrics on root URL

lib/kafkaex_lag_exporter/application.ex

@@ -0,0 +1,52 @@
+defmodule KafkaexLagExporter.Application do
+  # See https://hexdocs.pm/elixir/Application.html
+  # for more information on OTP Applications
+  @moduledoc false
+
+  use Application
+
+  @impl true
+  def start(_type, _args) do
+    consumer_group_opts = [
+      # setting for the ConsumerGroup
+      heartbeat_interval: 1_000,
+      # this setting will be forwarded to the GenConsumer
+      commit_interval: 1_000
+    ]
+
+    gen_consumer_impl = KafkaexLagExporter.ConsumerOffsetsGenConsumer
+    consumer_group_name = "offsets_group"
+    topic_names = ["__consumer_offsets"]
+
+    children = [
+      KafkaexLagExporter.PromEx,
+      # Start the Telemetry supervisor
+      KafkaexLagExporterWeb.Telemetry,
+      # Start the PubSub system
+      {Phoenix.PubSub, name: KafkaexLagExporter.PubSub},
+      # Start the Endpoint (http/https)
+      KafkaexLagExporterWeb.Endpoint,
+      # Start a worker by calling: KafkaexLagExporter.Worker.start_link(arg)
+      # {KafkaexLagExporter.Worker, arg}
+      %{
+        id: KafkaEx.ConsumerGroup,
+        start:
+          {KafkaEx.ConsumerGroup, :start_link,
+           [gen_consumer_impl, consumer_group_name, topic_names, consumer_group_opts]}
+      }
+    ]
+
+    # See https://hexdocs.pm/elixir/Supervisor.html
+    # for other strategies and supported options
+    opts = [strategy: :one_for_one, name: KafkaexLagExporter.Supervisor]
+    Supervisor.start_link(children, opts)
+  end
+
+  # Tell Phoenix to update the endpoint configuration
+  # whenever the application is updated.
+  @impl true
+  def config_change(changed, _new, removed) do
+    KafkaexLagExporterWeb.Endpoint.config_change(changed, removed)
+    :ok
+  end
+end