Configuration methods

You can change the settings of the Splunk Distribution of OpenTelemetry .NET in the following ways:

• For .NET applications, set environment variables. On Windows, set them in the process scope unless you want to activate automatic instrumentation globally for all .NET applications.

• For .NET Framework applications running as Windows services, you can add settings in the appSettings block of the app.config file when supported or set environment variables using the Windows Registry.

• For ASP.NET applications, add settings in the appSettings block of the web.config file. For example:

  <configuration>
     <appSettings>
        <add key="OTEL_SERVICE_NAME" value="my-service-name" />
     </appSettings>
  </configuration>

  Alternatively, you can set environment variables using any of the following methods:

  • Add the <environmentVariables> element in applicationHost.config for your application pools.

  • Set the environment variables for W3SVC and WAS.

• For ASP.NET Core applications, add <environmentVariable> elements inside the <aspNetCore> block of your web.config file.

General settings

The following settings are common to most instrumentation scenarios:

Exporter settings

The following settings control trace exporters and their endpoints:

.NET OTel settings for AlwaysOn Profiling

The following settings control the AlwaysOn Profiling feature for the .NET instrumentation:

Trace propagation settings

The following settings control trace propagation:

Samplers configuration

The following settings control trace sampling:

Resource detectors configuration

You can use resource detectors to retrieve additional attributes for your application’s spans.

The following settings control resource detectors:

The following resource detectors are available:

Instrumentation settings

The following settings control instrumentations and tracing behavior:

Server trace information

To connect Real User Monitoring (RUM) requests from mobile and web applications with server trace data, trace response headers are activated by default. The instrumentation adds the following response headers to HTTP responses:

Access-Control-Expose-Headers: Server-Timing
Server-Timing: traceparent;desc="00-<serverTraceId>-<serverSpanId>-01"

The Server-Timing header contains the traceId and spanId parameters in traceparent format. For more information, see the Server-Timing and traceparent documentation on the W3C website.

Diagnostic logging settings

The following settings control the internal logging of the Splunk Distribution of OpenTelemetry .NET:

Changing the default service name

By default, the Splunk Distribution of OpenTelemetry .NET retrieves the service name by trying the following steps until it succeeds:

1. The default service name is the name of the entry assembly. For example, the name of your .NET project file. For ASP.NET applications, the default service name is SiteName[/VirtualPath].

2. If the entry assembly is not available, the instrumentation tries to use the current process name. The process name can be dotnet if launched directly using an assembly. For example, dotnet InstrumentedApp.dll.

If all the steps fail, the service name defaults to unknown_service.

Environment variables for manual installation

When deploying the instrumentation manually, you need to make sure to set the following environment variables:

Windows (.NET)

Environment variable	Value
CORECLR_ENABLE_PROFILING	1
CORECLR_PROFILER	{918728DD-259F-4A6A-AC2B-B85E1B658318}
CORECLR_PROFILER_PATH_64	$installationLocation\win-x64\OpenTelemetry.AutoInstrumentation.Native.dll
CORECLR_PROFILER_PATH_32	$installationLocation\win-x86\OpenTelemetry.AutoInstrumentation.Native.dll
DOTNET_ADDITIONAL_DEPS	$installationLocation\AdditionalDeps
DOTNET_SHARED_STORE	$installationLocation\store
DOTNET_STARTUP_HOOKS	$installationLocation\net\OpenTelemetry.AutoInstrumentation.StartupHook.dll
OTEL_DOTNET_AUTO_HOME	$installationLocation
OTEL_DOTNET_AUTO_PLUGINS	Splunk.OpenTelemetry.AutoInstrumentation.Plugin, Splunk.OpenTelemetry.AutoInstrumentation

Windows (.NET Framework)

Environment variable	Value
COR_ENABLE_PROFILING	1
COR_PROFILER	{918728DD-259F-4A6A-AC2B-B85E1B658318}
COR_PROFILER_PATH_64	$installationLocation\win-x64\OpenTelemetry.AutoInstrumentation.Native.dll
COR_PROFILER_PATH_32	$installationLocation\win-x86\OpenTelemetry.AutoInstrumentation.Native.dll
OTEL_DOTNET_AUTO_HOME	$installationLocation
OTEL_DOTNET_AUTO_PLUGINS	Splunk.OpenTelemetry.AutoInstrumentation.Plugin, Splunk.OpenTelemetry.AutoInstrumentation

Linux (.NET)

Environment variable	Value
CORECLR_ENABLE_PROFILING	1
CORECLR_PROFILER	{918728DD-259F-4A6A-AC2B-B85E1B658318}
CORECLR_PROFILER_PATH	$INSTALL_DIR/linux-x64/OpenTelemetry.AutoInstrumentation.Native.so (glibc) $INSTALL_DIR/linux-musl-x64/OpenTelemetry.AutoInstrumentation.Native.so (musl)
DOTNET_ADDITIONAL_DEPS	$INSTALL_DIR\AdditionalDeps
DOTNET_SHARED_STORE	$INSTALL_DIR\store
DOTNET_STARTUP_HOOKS	$INSTALL_DIR\net\OpenTelemetry.AutoInstrumentation.StartupHook.dll
OTEL_DOTNET_AUTO_HOME	$INSTALL_DIR
OTEL_DOTNET_AUTO_PLUGINS	Splunk.OpenTelemetry.AutoInstrumentation.Plugin, Splunk.OpenTelemetry.AutoInstrumentation

Note: The default installation path on Linux is $HOME/.otel-dotnet-auto.