Plug and Phoenix

You can capture errors in Plug and Phoenix applications with Sentry.PlugContext and Sentry.PlugCapture.

Sentry.PlugContext adds contextual metadata from the current request to the reported errors that happen during Plug execution. For Cowboy applications, an additional plug Sentry.PlugCapture is required to ensure this metadata propagates properly.

Phoenix Configuration

If you are using Phoenix, follow these steps to add the Plug integration:

1. Add Sentry.PlugContext below Plug.Parsers.

defmodule MyAppWeb.Endpoint
   use Phoenix.Endpoint, otp_app: :my_app

   # ...

   plug Plug.Parsers,
     parsers: [:urlencoded, :multipart, :json],
     pass: ["*/*"],
     json_decoder: Phoenix.json_library()

+  plug Sentry.PlugContext

2. If you're using Cowboy, add Sentry.PlugCapture above the use Phoenix.Endpoint line in your endpoint file.

defmodule MyAppWeb.Endpoint
+  use Sentry.PlugCapture
   use Phoenix.Endpoint, otp_app: :my_app

   # ...

If you're also using Phoenix LiveView, consider also setting up your LiveViews to use the Sentry.LiveViewHook hook (available in the Sentry SDK versions 10.5.0 and higher):

defmodule MyAppWeb do
  def live_view do
    quote do
      use Phoenix.LiveView

      on_mount Sentry.LiveViewHook
    end
  end
end

Capturing User Feedback

If you would like to capture user feedback, the Sentry.get_last_event_id_and_source/0 function can be used to see if Sentry has sent an event within the current Plug process (and get the source of that event). :plug will be the source for events coming from Sentry.PlugCapture. The options described in the Sentry documentation linked above can be encoded into the response as well.

Below is an example Phoenix application setup that displays the user feedback form on 500 responses on requests accepting HTML:

defmodule MyAppWeb.ErrorView do
  # ...

  def render("500.html", _assigns) do
    case Sentry.get_last_event_id_and_source() do
      {event_id, :plug} when is_binary(event_id) ->
        opts = Jason.encode!(%{eventId: event_id})

        ~E"""
        <script src="https://browser.sentry-cdn.com/5.9.1/bundle.min.js" integrity="sha384-/x1aHz0nKRd6zVUazsV6CbQvjJvr6zQL2CHbQZf3yoLkezyEtZUpqUNnOLW9Nt3v" crossorigin="anonymous"></script>
        <script>
          Sentry.init({ dsn: '<%= Sentry.get_dsn() %>' });
          Sentry.showReportDialog(<%= raw opts %>)
        </script>
        """

      _ ->
        "Error"
    end
  end
end

Plug Configuration

If you have a non-Phoenix application, follow these steps to configure the Plug integration:

1. Add Sentry.PlugContext below Plug.Parsers (if it is in your stack).

 defmodule MyApp.Router do
   use Plug.Router

   # ...

   plug Plug.Parsers,
     parsers: [:urlencoded, :multipart]

+  plug Sentry.PlugContext

2. If you're using Cowboy, add Sentry.PlugCapture at the top of your Plug application.

 defmodule MyApp.Router do
   use Plug.Router
+  use Sentry.PlugCapture

   # ...