Examples of using DocumentListener with OpenTelemetry

[STRUDSO]

• CorrelationListener
• Events listener

[jeremydmiller]

@STRUDSO Can you start by explaining why all of Marten's existing Otel support doesn't cover whatever you want here?
https://martendb.io/otel.html#open-telemetry-and-metrics

[STRUDSO]

Let me spend a little more time with this, and yes some of it probably belongs in Samples.

At first i didn't realize the work in:

marten/src/Marten/ISessionFactory.cs

Line 46 in a0b339a

documentSession.CorrelationId = Activity.Current?.RootId;

Spent some time on understanding traceparent, trace_id and parent_id in the context of this:
https://www.w3.org/TR/trace-context/#version-format
And how it manifests itself in dotnet's activity class.

In SessionFactoryBase it has:

        documentSession.CorrelationId = Activity.Current?.RootId;

RootId = TraceId in my understanding, so all good, don't know anything about tracing pre opentelemetry, so maybe this is how it should be. But seems like opentelemetry calls it traceid. i guess this is what you would use to find "all" of the spans in jaeger eg.

        documentSession.CausationId = Activity.Current?.ParentId;

ParentId i don't fully understand, my understanding is:

using var activity1 = source.Start
using var activity2 = source.Start
// activity2.ParentId == activity.Id
using var session = store.OpenSession()
session.Store(doc)

then doc.CausationId would point to the Id of activity1.
Shouldn't this be activity2.Id?