opentelemetry_oban: Add Attribute for Time Spent in Queue

[bradschwartz]

Is your feature request related to a problem? Please describe.

Something I'm interesting in keeping track of is how much time a job has spent waiting in the queue since being scheduled. I would be able to use this as an indicator to know if my workers are taking longer than typical to process jobs.

Describe the solution you'd like

I would just add a new attribute in the handle_job_start function here.

Something like:

diff --git a/instrumentation/opentelemetry_oban/lib/opentelemetry_oban/job_handler.ex b/instrumentation/opentelemetry_oban/lib/opentelemetry_oban/job_handler.ex
index 8d14f78..b31a989 100644
--- a/instrumentation/opentelemetry_oban/lib/opentelemetry_oban/job_handler.ex
+++ b/instrumentation/opentelemetry_oban/lib/opentelemetry_oban/job_handler.ex
@@ -70,7 +70,8 @@ defmodule OpentelemetryOban.JobHandler do
       :"oban.job.attempt" => attempt,
       :"oban.job.max_attempts" => max_attempts,
       :"oban.job.inserted_at" => DateTime.to_iso8601(inserted_at),
-      :"oban.job.scheduled_at" => DateTime.to_iso8601(scheduled_at)
+      :"oban.job.scheduled_at" => DateTime.to_iso8601(scheduled_at),
+      :"oban.job.queue_time_ms" => DateTime.diff(DateTime.utc_now(), scheduled_at, :millisecond)
     }
 
     span_name = "#{worker} process"

Describe alternatives you've considered Continue to just calculate and add this attribute by hand manually.

Additional context Add any other context or screenshots about the feature request here.