Exception management in liveview render good practice

Phoenix Forum Questions / Help
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1

Hello !

The goal is to have all exception that occurs and send it to an external service, like sentry.

I managed to catch them for:

  • exceptions when user is not connected
  • exceptions during mount, liveview handle_event, live_component handle_event and handle_params

But I can’t catch when:

  • exceptions during render

I could move all my heex into a render function, and manual catch for each render, but it would be very unpleasant.

I had hard time finding anything about good practice about it with liveview, I feel like I’m missing something obvious. My current approach is not good since it is very easy to forget something.

Anyone had the same trouble and found a graceful way of managing this ?

Have a nice day !

2

I do use sentry and I do catch exceptions on render in prod by setting elixir sentry flag to catch logger exceptions.

“Capture crashed process exceptions” iirc.

Hope this helps

3

That’s a fair point ! will give it a try. Thanks.

1 Like
4

Some final feedbacks:

Tried using the “catch all” from sentry, but it catch way too much thing, (if a render fail, I have multiple Logger.error that occurs (one from phoenix’s GenServer, the one from raise, etc…).

The sentry became polluted very fast on any Logger.error.

My current solution: write my own little Logger backend :

defmodule MyApp.SentryBackend do
  @behaviour :gen_event

  def init(__MODULE__), do: {:ok, nil}

  def handle_call({:configure, _options}, state), do: {:ok, :ok, state}

  # only Logger errors with crash_reason
  def handle_event({level, _gl, {Logger, _msg, _ts, meta}}, state) when level in [:emergency, :alert, :critical, :error] do
    if meta[:crash_reason] do
      {reason, stacktrace} = meta[:crash_reason]
      Sentry.capture_message(inspect(reason), stacktrace: stacktrace)
    end

    {:ok, state}
  end

  def handle_event(_, state), do: {:ok, state}

  def terminate(_reason, _state), do: :ok
end

I allows my to further filter if I need to.

cheers !