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How to Monitor Your Elixir Phoenix Application with Vigilmon

#elixir #phoenix #webdev #monitoring

How to Monitor Your Elixir Phoenix Application with Vigilmon

Elixir and Phoenix are known for fault tolerance — but "let it crash" still requires knowing when something crashed. Vigilmon provides external uptime monitoring for Phoenix applications.

Create a Health Check Endpoint

Add a health route to your Phoenix router:

# lib/my_app_web/router.ex
scope "/", MyAppWeb do
  pipe_through :api
  get "/health", HealthController, :check
end
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Create the controller:

# lib/my_app_web/controllers/health_controller.ex
defmodule MyAppWeb.HealthController do
  use MyAppWeb, :controller

  def check(conn, _params) do
    db_status = check_database()
    overall = if db_status == :ok, do: :ok, else: :degraded
    http_status = if overall == :ok, do: 200, else: 503

    conn
    |> put_status(http_status)
    |> json(%{status: overall, database: db_status})
  end

  defp check_database do
    case MyApp.Repo.query("SELECT 1") do
      {:ok, _} -> :ok
      {:error, _} -> :error
    end
  end
end
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Plug-Based Health Check (Lightweight Option)

For minimal overhead, use a Plug directly:

defmodule MyApp.HealthPlug do
  import Plug.Conn

  def init(opts), do: opts

  def call(%Plug.Conn{request_path: "/health"} = conn, _opts) do
    conn
    |> put_resp_content_type("application/json")
    |> send_resp(200, ~s({"status":"ok"}))
    |> halt()
  end

  def call(conn, _opts), do: conn
end
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Add it to your endpoint before the Router:

# lib/my_app_web/endpoint.ex
plug MyApp.HealthPlug
plug MyAppWeb.Router
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Add to Vigilmon

  1. Sign up at vigilmon.online
  2. Add monitor: https://your-phoenix-app.com/health
  3. Set 1-minute interval
  4. Add Slack or email alert

Monitoring OTP Supervisors

Elixir's OTP restarts crashed processes automatically — but if a supervisor hits its max restart intensity, it stops. Add supervisor health to your endpoint:

defp check_supervisor do
  if Process.whereis(MyApp.Supervisor) != nil, do: :ok, else: :error
end
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Vigilmon will alert you if the health check returns 503 — catching OTP-level failures before users notice.

Free Tier

Get started free at vigilmon.online — 5 monitors, 1-minute intervals, email and Slack alerts.

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