opentelemetry_ecto - add possibility to setup additional attributes.

[fcevado]

current implementation of opentelemetry_ecto doesn't allow to setup additional attributes to the span. this PR add this possibility by allowing an :attributes option on setup.

[linux-foundation-easycla]

The committers listed above are authorized under a signed CLA.

• ✅ login: fcevado / name: cevado (a211c62, 13e7acb)

[andrewhr]

Isn't this task better suited for #85?

The concern is this become a pattern for all instrumentation libraries. Not sure how it's the vision for that, specially after the Instrumentation Scope changes. Thoughts @tsloughter?

[tsloughter]

@andrewhr that would assume they want the attributes to also be in baggage.

[fcevado]

@andrewhr as I understand baggage would be generic for the whole app not particular to a library context. for example, if I want to identify write and read replicas, I can specify different telemetry_prefix for the repos and setup the instrumentation with specific attributes to them. the same for applications that connect to multiple databases and i want something more descriptive than the db.url.

[fcevado]

@tsloughter @bryannaegele any update on this?

[tsloughter]

I think this is needed but I don't want to be the decided on a change like this to the Ecto integration.

But I'll give an argument for it in principle: in other cases, like an HTTP server span, you can add attributes to the Span the instrumentation creates because the user is writing the code that is being wrapped in a span (so simply call the set_attribute macro on the current context). But in the case of an instrumentation like Ecto the control is never given to the user because it simply runs the query.

[bryannaegele]

Sorry. I was on vacation when you were still working through those conversations.

I think this is fine at this point? The functionality is required by the spec now. Did you have any specific objection to the implementation @tsloughter?

[bryannaegele]

Also, @fcevado you still need to sign the CLA.

[tsloughter]

Looks ok to me.

[fcevado]

@bryannaegele it's signed 👍