What's the new guideline for using metrics?

[Christian Nagel (christiannagel)]

Because the OpenTelemetry metrics library is not stable yet (e.g. #3087), the configuration from the ServiceDefaults project, and from the components has been removed. What is the new guideline to configure what metrics should be shown with the dashboard, also custom meters?

[David Fowler (davidfowl)]

Specifically for event counters right?

[Dan Moseley (danmoseley)]

Cc James Newton-King (@JamesNK)

[David Fowler (davidfowl)]

Aspire component still have metrics, just not event counter based metrics. The native metric APIs (Meter) are still turned on by default if a component provides them.

[Christian Nagel (christiannagel)]

Now I see, EF Core is still using the old EventSource API (https://github.com/dotnet/efcore/blob/45448efb1da8914489739bc4116f7a8f6c9374a2/src/EFCore/Infrastructure/EntityFrameworkEventSource.cs#L11) and not the new Meter API.
Metrics from components using the EventSource API, such as the Microsoft Entity Framework Core Cosmos DB component is no longer available, that's why the Metrics property has been removed with these components (364ce50) - is this correct?

I've been using the Metrics property with these components, and was thinking it's been removed with all components, but this seems not to be the case.

What's the reason for this change?
Going forward, all the components (e.g. EF Core) using event counter-based metrics (EventSource) should switch to the new Meter API, is this correct?

[James Newton-King (JamesNK)]

OpenTelemetry.Instrumentation.EventCounters is a pre-release package. We can't keep referencing once Aspire components are not pre-release.

I think eventually EF Core and friends will publish real metrics, but until then you'll have to reference the event counters package and add the counters in your app.

[Christian Nagel (christiannagel)]

Thanks James Newton-King (@JamesNK)! I wasn't aware OpenTelemetry.Instrumentation.EventCounters is the only option to use event counters. dotnet counters supports monitoring with EventSource counters as well. Before .NET 6, event counters were the only option we had with .NET.

More reasons to switch to the new Meter API :-)

With EF Core I've seen it's in the .NET 9 milestone: dotnet/efcore#25880