Dynamically adding/removing instruments to a meter at runtime.

[Simonl9l]

Hi, trying to switch over to Open Telemetry from System.Metrics.Diagnostics, to using the DI service builder, and AddOpenTelemtry() etc.

Is there a way to dynamically add or remove instruments, at runtime? How about same for Metrics?

My application can hot reload configuration that determined what metrics and instruments are created, so not sure how to do this if its not know at startup.

Thanks!

[RassK]

@Simonl9l OTel SDK officially does not support this. You may do similar what we do in OTel Auto for "lazy instrumentation". Start from here https://github.com/open-telemetry/opentelemetry-dotnet-instrumentation/blob/main/src/OpenTelemetry.AutoInstrumentation/Loading/LazyInstrumentationLoader.cs

[Simonl9l]

Hi @RassK - thanks for the reply (applogies it's taken while to get back to you).

On initial inspection of the LazyLoader, and trying to track back though the Repo, I'm not finding how this ties back to the AddOpenTeletmetry() and the builder as part of startup code. It's all bit of a fire hose.

A few more hints would be hugely appreciated is you could perhaps provide a small example to get me going!

[RassK]

It's a standalone part. No connection to AddOpenTelemetry() but AddSource().

LazyInstrumentationLoader is just stateholder of Initializers (for example HttpClientInitializer). Initializer specifies when an specific instrumentation instance is created and when invoked, then creates the instance.

For eg HttpClientInitializer is waiting for System.Net.Http.dll to load. If loaded it creates instance of OpenTelemetry.Instrumentation.Http.HttpClientInstrumentation.

EnvironmentConfigurationTracerHelper.Wrappers.AddHttpClientInstrumentation() wires up all the parts. First adds a lazy initializer to listen for assembly load events. Second always subscribes to System.Diagnostic.DiagnosticSource sources (since you cannot subscribe after ProviderBuilder is built).