Good to hear! Would you mind sharing your solution?

Emitted here:

https://github.com/phoenixframework/phoenix/blob/ea10baae82a9b849b9b4b4c1977dcfc344662863/installer/templates/phx_web/endpoint.ex#L43

All events documented here:

https://github.com/phoenixframework/phoenix/blob/60da3f0dc01b7e0eae0e5bd608431ead953ded5d/lib/phoenix/logger.ex

Yeah, I was completely reading the docs wrong.

summary("phoenix.endpoint.stop.duration",
  tag_values: &Monitoring.log_http_request/4,
  unit: {:native, :millisecond}
),

The tag_values fun isn’t what gets triggered for event processing like I thought it was. That’s used to transform the data in the event to something else it looks like.

What I actually needed to do was subscribe to the event like:

:telemetry.attach("log_request", [:phoenix, :endpoint, :stop], &Monitoring.log_http_request/4, :no_config)

I also needed to make sure I was doing it in a place that was actually called. I was placing this in Telemetry.metrics, but that function was never called so I wasn’t actually subscribing to the event.