Difficulties in Exception reporting migrating from Spandex to OTel

[apreifsteck]

Describe the bug
I recently experimented with adding open telemetry to one of the apps my team owns. It's been over a week now since I made the swap and we've had a few exceptions. However, they all show up in DataDog with no stacktrace info and this message: exit:{{#{'__exception__' => true,...},[...]},{'Elixir.MyAppWeb.Endpoint',...}}.

It looks like the exceptions are coming in as events, which as far as I know is compliant with the OTel spec.

It seems like Datadog doesn't handle errors this way, and instead they're included as span attributes (sorry about the redaction, point being is that there is a message and a full stacktrace there)

It looks like I might need to add a span processor to add that span attribute. Perhaps this is more of a compatibility issue than anything else. Regardless, if this issue results in a bridge library or a migration guide to follow for Spandex, that would be much appreciated. Of course, I'd be happy to collaborate in any way I can!

Expected behavior
I had expected something like what Spandex presents.

Also, it seems like the exception.message attribute is missing on the event.

Additional context

• Using Collector
• Elixir 14.4
• Datadog for APM
• Migrating from Spandex
• Issue out of discussion
  Packages:

      {:opentelemetry, "~> 1.3"},
      {:opentelemetry_api, "~> 1.2"},
      {:open_telemetry_decorator, "~> 1.4"},
      {:opentelemetry_exporter, "~> 1.6"},
      {:opentelemetry_phoenix, "~> 1.1"},
      {:opentelemetry_ecto, "~> 1.2"},
      {:opentelemetry_cowboy, "~> 0.3"},

[apreifsteck]

Upon doing some further experimentation, it looks like error reporting happens pretty well if the exception occurs inside a manually instrumented trace but not so good if it bubbles up to Cowboy.

On a whim I was going to try switching out to Bandit to see what that did. It looks like the Phoenix Telemetry package on Hex (1.2) doesn't support that yet, although it looks like there was a PR #249 not too long ago that added this. Is a new release for Phoenix Telemetry coming soon, by any chance?

[grzuy]

I suspect the following recent changes

https://github.com/open-telemetry/opentelemetry-erlang-contrib/pull/359/files#diff-4c2fd05f88775967cc821a019b047da19e9ab6db7a8a88a82fa6b3db5350b7bcR391-R422

should have fixed this issue.

I think it's released in opentelemetry_cowboy v1.0.0-rc.1.

@apreifsteck can you confirm?