Default exporter immediately attempts on start connect to
`:otel-collector` default port. As we don't have any collector running
on our test environment, this results in a few warnings. That's not an
issue in itself, as code immediately switches to another export, but
creates a lot of noise.
This patch moves the exporter setup to `config/test.exs`, essentially
removing the need to restart opentelemetry applicationn for each test
case. The only work setup blocks do is update the exporter's target pid.
The processor was changed to simple mode, available now, which also remove
another vector of (unlikely but theoretically possible) race-conditions.
There is an edge case, if you use `forward/4` and use Plug.ErrorHandler,
then when an exception reaches the outer router, then Plug.send_resp
will be called, triggering `[:phoenix, :endpoint, :stop]`, and the span
will be gone by the time the outer router gets the exception. This
causes this telemetry handler to crash and be detached.
Sequence of events:
- [:phoenix, :endpoint, :start]
- [:phoenix, :router_dispatch, :exception] (inner router)
- [:phoenix, :endpoint, :stop]
- [:phoenix, :router_dispatch, :exception] (outer router) ** here there is no span, crashes
Yordis Prieto
Andrew Rosa
Derek Kraan
Bryan Naegele
Ho-Yon Mak
Timmo Verlaan