Auto instrumention - Metrics work, traces not received

[forloop (Russ Cam)]

@Jbezemer

That makes a lot of sense..I thought I disabled all code/applications that instantiated APM through a .Net library. I'll go over it again, perhaps some code was left behind or an older version is still active.

It can sometimes come about very surreptitiously

For more context, the profiler injects a shim assembly that loads a supporting managed assembly containing the code for auto instrumentation. One of the first operations it does is to ensure the singleton agent instance is initialized:

elastic/apm-agent-dotnet/blob/4d0002bdf479e1d170ca5fd8d8bd57c148eef42b/src/Elastic.Apm.Profiler.Managed/AutoInstrumentation.cs#L19-L53

In the case of .NET Framework running in a hosted environment e.g. IIS, it defers instantiation to the ASP.NET integration, which in turn, will end up instantiating the agent in the ElasticApmModule that it registers in the ASP.NET pipeline:

elastic/apm-agent-dotnet/blob/4d0002bdf479e1d170ca5fd8d8bd57c148eef42b/src/Elastic.Apm.Profiler.Managed/Integrations/AspNet/ElasticApmModuleIntegration.cs#L52-L75

This is primarily done to allow the agent to be configured with ASP.NET specific components.

Now, if for some reason, you wanted to explicitly register ElasticApmModule yourself in web.config, and ultimately control the instantiation of the agent instead of leaving it to the profiler, you could as an alternative, disable the ASP.NET auto instrumentation integration with the Elastic APM profiler environment variable:

ELASTIC_APM_PROFILER_EXCLUDE_INTEGRATIONS=AspNet