config.md

Configuration

Configuration methods

You can apply configuration settings in the following ways, with environment variables taking precedence over App.config or Web.config file:

1. Environment variables

   Environment variables are the main way to configure the settings.

2. App.config or Web.config file

   For an application running on .NET Framework, you can use a web configuration file (web.config) or an application configuration file (app.config) to configure the OTEL_* settings.

   ⚠️ Only settings starting with OTEL_ can be set using App.config or Web.config. However, the following settings are not supported:

   • OTEL_DOTNET_AUTO_HOME
   • OTEL_DOTNET_AUTO_EXCLUDE_PROCESSES
   • OTEL_DOTNET_AUTO_INTEGRATIONS_FILE
   • OTEL_DOTNET_AUTO_[TRACES|METRICS|LOGS]_[ENABLED|DISABLED]_INSTRUMENTATIONS
   • OTEL_DOTNET_AUTO_LOG_DIRECTORY
   • OTEL_DOTNET_AUTO_DEBUG
   • OTEL_DOTNET_AUTO_NETFX_REDIRECT_ENABLED

   Example with OTEL_SERVICE_NAME setting:

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

By default we recommend using environment variables for configuration. However, if given setting supports it, then:

• use Web.config for configuring an ASP.NET application (.NET Framework),
• use App.config for configuring a Windows Service (.NET Framework).

Global settings

Environment variable	Description	Default value
OTEL_DOTNET_AUTO_HOME	Installation location.
OTEL_DOTNET_AUTO_EXCLUDE_PROCESSES	Names of the executable files that the profiler cannot instrument. Supports multiple comma-separated values, for example: ReservedProcess.exe,powershell.exe. If unset, the profiler attaches to all processes by default.

Resources

A resource is the immutable representation of the entity producing the telemetry. See Resource semantic conventions for more details.

Environment variable	Description	Default value
OTEL_RESOURCE_ATTRIBUTES	Key-value pairs to be used as resource attributes. See Resource SDK for more details.	See Resource semantic conventions for details.
OTEL_SERVICE_NAME	Sets the value of the service.name resource attribute. If service.name is provided in OTEL_RESOURCE_ATTRIBUTES, the value of OTEL_SERVICE_NAME takes precedence.	unknown_service:%ProcessName%

Instrumentations

All instrumentations are enabled by default for all signal types (traces, metrics, and logs).

You can disable all instrumentations for a specific signal type by setting the OTEL_DOTNET_AUTO_{SIGNAL}_INSTRUMENTATION_ENABLED environment variable to false.

For a more granular approach, you can disable specific instrumentations for a given signal type by setting the OTEL_DOTNET_AUTO_{SIGNAL}_{0}_INSTRUMENTATION_ENABLED environment variable to false, where {SIGNAL} is the type of signal, for example TRACES, and {0} is the case-sensitive name of the instrumentation.

Environment variable	Description	Default value
OTEL_DOTNET_AUTO_INTEGRATIONS_FILE	List of bytecode instrumentations JSON configuration filepaths, delimited by the platform-specific path separator (; on Windows, : on Linux and macOS). For example: %ProfilerDirectory%/integrations.json. It is required for bytecode instrumentations.
OTEL_DOTNET_AUTO_INSTRUMENTATION_ENABLED	Disables all instrumentations.	true
OTEL_DOTNET_AUTO_TRACES_INSTRUMENTATION_ENABLED	Disables all trace instrumentations. Overrides OTEL_DOTNET_AUTO_INSTRUMENTATION_ENABLED.	Inherited from the current value of OTEL_DOTNET_AUTO_INSTRUMENTATION_ENABLED
OTEL_DOTNET_AUTO_TRACES_{0}_INSTRUMENTATION_ENABLED	Configuration pattern for enabling or disabling a specific trace instrumentation, where {0} is the uppercase id of the instrumentation you want to enable. Overrides OTEL_DOTNET_AUTO_TRACES_INSTRUMENTATION_ENABLED.	Inherited from the current value of OTEL_DOTNET_AUTO_TRACES_INSTRUMENTATION_ENABLED
OTEL_DOTNET_AUTO_METRICS_INSTRUMENTATION_ENABLED	Disables all metric instrumentations. Overrides OTEL_DOTNET_AUTO_INSTRUMENTATION_ENABLED.	Inherited from the current value of OTEL_DOTNET_AUTO_INSTRUMENTATION_ENABLED
OTEL_DOTNET_AUTO_METRICS_{0}_INSTRUMENTATION_ENABLED	Configuration pattern for enabling or disabling a specific metric instrumentation, where {0} is the uppercase id of the instrumentation you want to enable. Overrides OTEL_DOTNET_AUTO_METRICS_INSTRUMENTATION_ENABLED.	Inherited from the current value of OTEL_DOTNET_AUTO_METRICS_INSTRUMENTATION_ENABLED
OTEL_DOTNET_AUTO_LOGS_INSTRUMENTATION_ENABLED	Disables all log instrumentations. Overrides OTEL_DOTNET_AUTO_INSTRUMENTATION_ENABLED.	Inherited from the current value of OTEL_DOTNET_AUTO_INSTRUMENTATION_ENABLED
OTEL_DOTNET_AUTO_LOGS_{0}_INSTRUMENTATION_ENABLED	Configuration pattern for enabling or disabling a specific log instrumentation, where {0} is the uppercase id of the instrumentation you want to enable. Overrides OTEL_DOTNET_AUTO_LOGS_INSTRUMENTATION_ENABLED.	Inherited from the current value of OTEL_DOTNET_AUTO_LOGS_INSTRUMENTATION_ENABLED

Traces instrumentations

ID	Instrumented library	Supported versions	Instrumentation type
ASPNET	ASP.NET (.NET Framework) MVC / WebApi [1] Not supported on .NET	*	source
ASPNETCORE	ASP.NET Core Not supported on .NET Framework	*	source
ELASTICSEARCH	Elastic.Clients.Elasticsearch	≥8.0.0	source
ENTITYFRAMEWORKCORE	Microsoft.EntityFrameworkCore Not supported on .NET Framework	≥6.0.12	source
GRAPHQL	GraphQL	≥2.3.0 & < 3.0.0	bytecode
GRPCNETCLIENT	Grpc.Net.Client	≥2.43.0 & < 3.0.0	source
HTTPCLIENT	System.Net.Http.HttpClient and System.Net.HttpWebRequest	*	source
QUARTZ	Quartz Not supported on .NET Framework 4.7.1 and older	≥3.4.0	source
MASSTRANSIT	MassTransit Not supported on .NET Framework	≥8.0.0	source
MONGODB	MongoDB.Driver.Core Not supported on .NET Framework	≥2.13.3 & < 3.0.0	source & bytecode
MYSQLDATA	MySql.Data Not supported on .NET Framework	≥6.10.7	source & bytecode [2]
NPGSQL	Npgsql	≥6.0.0	source
NSERVICEBUS	NServiceBus	≥8.0.0	source & bytecode
SQLCLIENT	Microsoft.Data.SqlClient and System.Data.SqlClient	* [3]	source
STACKEXCHANGEREDIS	StackExchange.Redis Not supported on .NET Framework	≥2.0.405 < 3.0.0	source & bytecode
WCF	System.ServiceModel No support for server side on .NET. For configuration see WCF Instrumentation Configuration	* [4]	source

[1]: Only integrated pipeline mode is supported.

[2]: MySql.Data 8.0.31 and higher requires bytecode instrumentation.

[3]: Microsoft.Data.SqlClient v3.* is not supported on .NET Framework, due to issue.

[4]: On .NET it supports System.ServiceModel.Primitives ≥ 4.7.0.

Metrics instrumentations

ID	Instrumented library	Supported versions	Instrumentation type
ASPNET	ASP.NET Framework [1] Not supported on .NET	*	source
ASPNETCORE	ASP.NET Core [2] Not supported on .NET Framework	*	source
HTTPCLIENT	System.Net.Http.HttpClient and System.Net.HttpWebRequest	*	source
NETRUNTIME	OpenTelemetry.Instrumentation.Runtime	*	source
PROCESS	OpenTelemetry.Instrumentation.Process	*	source
NSERVICEBUS	NServiceBus	≥8.0.0	source & bytecode

[1]: The ASP.NET metrics are generated only if the AspNet trace instrumentation is also enabled.

[2]: This instrumentation automatically enables the Microsoft.AspNetCore.Hosting.HttpRequestIn spans.

Logs instrumentations

ID	Instrumented library	Supported versions	Instrumentation type
ILOGGER	Microsoft.Extensions.Logging Not supported on .NET Framework	≥6.0.0	bytecode or source [1]

[1]: For ASP.NET Core applications, the LoggingBuilder instrumentation can be enabled without using the .NET CLR Profiler by setting the ASPNETCORE_HOSTINGSTARTUPASSEMBLIES environment variable to OpenTelemetry.AutoInstrumentation.AspNetCoreBootstrapper.

Instrumentation options

Environment variable	Description	Default value
OTEL_DOTNET_AUTO_GRAPHQL_SET_DOCUMENT	Whether GraphQL instrumentation can pass raw queries as graphql.document attribute. This may contain sensitive information and therefore is disabled by default.	false

Propagators

Propagators allow applications to share context. See the OpenTelemetry specification for more details.

Environment variable	Description	Default value
OTEL_PROPAGATORS	Comma-separated list of propagators. Supported options: tracecontext, baggage, b3multi, b3. See the OpenTelemetry specification for more details.	tracecontext,baggage

Samplers

Samplers let you control potential noise and overhead introduced by OpenTelemetry instrumentation by selecting which traces you want to collect and export. See the OpenTelemetry specification for more details.

Environment variable	Description	Default value
OTEL_TRACES_SAMPLER	Sampler to be used for traces [1]	parentbased_always_on
OTEL_TRACES_SAMPLER_ARG	String value to be used as the sampler argument [2]

[1]: Supported values are:

• always_on,
• always_off,
• traceidratio,
• parentbased_always_on,
• parentbased_always_off,
• parentbased_traceidratio.

[2]: For traceidratio and parentbased_traceidratio samplers: Sampling probability, a number in the [0..1] range, e.g. "0.25". Default is 1.0.

Exporters

Exporters output the telemetry.

Environment variable	Description	Default value
OTEL_TRACES_EXPORTER	Traces exporter to be used. The value can be one of the following: zipkin, otlp, none.	otlp
OTEL_METRICS_EXPORTER	Metrics exporter to be used. The value can be one of the following: otlp, prometheus, none.	otlp
OTEL_LOGS_EXPORTER	Logs exporter to be used. The value can be one of the following: otlp, none.	otlp

Traces exporter

Environment variable	Description	Default value
OTEL_BSP_SCHEDULE_DELAY	Delay interval (in milliseconds) between two consecutive exports.	5000
OTEL_BSP_EXPORT_TIMEOUT	Maximum allowed time (in milliseconds) to export data	30000
OTEL_BSP_MAX_QUEUE_SIZE	Maximum queue size.	2048
OTEL_BSP_MAX_EXPORT_BATCH_SIZE	Maximum batch size. Must be less than or equal to OTEL_BSP_MAX_QUEUE_SIZE.	512

Metrics exporter

Environment variable	Description	Default value
OTEL_METRIC_EXPORT_INTERVAL	The time interval (in milliseconds) between the start of two export attempts.	60000 for OTLP exporter, 10000 for console exporter
OTEL_METRIC_EXPORT_TIMEOUT	Maximum allowed time (in milliseconds) to export data.	30000 for OTLP exporter, none for console exporter

Logs exporter

Environment variable	Description	Default value
OTEL_DOTNET_AUTO_LOGS_INCLUDE_FORMATTED_MESSAGE	Whether the formatted log message should be set or not.	false

OTLP

To enable the OTLP exporter, set the OTEL_TRACES_EXPORTER/OTEL_METRICS_EXPORTER/OTEL_LOGS_EXPORTER environment variable to otlp.

To customize the OTLP exporter using environment variables, see the OTLP exporter documentation. Important environment variables include:

Environment variable	Description	Default value
OTEL_EXPORTER_OTLP_ENDPOINT	Target endpoint for the OTLP exporter. See the OpenTelemetry specification for more details.	http://localhost:4318 for the http/protobuf protocol, http://localhost:4317 for the grpc protocol
OTEL_EXPORTER_OTLP_PROTOCOL	OTLP exporter transport protocol. Supported values are grpc, http/protobuf. [1]	http/protobuf
OTEL_EXPORTER_OTLP_TIMEOUT	The max waiting time (in milliseconds) for the backend to process each batch.	10000
OTEL_EXPORTER_OTLP_HEADERS	Comma-separated list of additional HTTP headers sent with each export, for example: Authorization=secret,X-Key=Value.
OTEL_ATTRIBUTE_VALUE_LENGTH_LIMIT	Maximum allowed attribute value size.	none
OTEL_ATTRIBUTE_COUNT_LIMIT	Maximum allowed span attribute count.	128
OTEL_SPAN_ATTRIBUTE_VALUE_LENGTH_LIMIT	Maximum allowed attribute value size. Not applicable for metrics..	none
OTEL_SPAN_ATTRIBUTE_COUNT_LIMIT	Maximum allowed span attribute count. Not applicable for metrics..	128
OTEL_SPAN_EVENT_COUNT_LIMIT	Maximum allowed span event count.	128
OTEL_SPAN_LINK_COUNT_LIMIT	Maximum allowed span link count.	128
OTEL_EVENT_ATTRIBUTE_COUNT_LIMIT	Maximum allowed attribute per span event count.	128
OTEL_LINK_ATTRIBUTE_COUNT_LIMIT	Maximum allowed attribute per span link count.	128

[1]: Considerations on the OTEL_EXPORTER_OTLP_PROTOCOL:

• The OpenTelemetry .NET Automatic Instrumentation defaults to http/protobuf, which differs from the OpenTelemetry .NET SDK default value of grpc.
• On .NET 6 and higher, the application must reference Grpc.Net.Client to use the grpc OTLP exporter protocol. For example, by adding <PackageReference Include="Grpc.Net.Client" Version="2.43.0" /> to the .csproj file.
• On .NET Framework, the grpc OTLP exporter protocol is not supported.

Prometheus

⚠️ Do NOT use in production.

Prometheus exporter is intended for the inner dev loop. Production environments can use a combination of OTLP exporter with OpenTelemetry Collector having otlp receiver and prometheus exporter.

To enable the Prometheus exporter, set the OTEL_METRICS_EXPORTER environment variable to prometheus.

The exporter exposes the metrics HTTP endpoint on http://localhost:9464/metrics and it caches the responses for 300 milliseconds.

See the Prometheus Exporter HttpListener documentation. to learn more.

Zipkin

To enable the Zipkin exporter, set the OTEL_TRACES_EXPORTER environment variable to zipkin.

To customize the Zipkin exporter using environment variables, see the Zipkin exporter documentation. Important environment variables include:

Environment variable	Description	Default value
OTEL_EXPORTER_ZIPKIN_ENDPOINT	Zipkin URL	http://localhost:9411/api/v2/spans

Additional settings

Environment variable	Description	Default value
OTEL_DOTNET_AUTO_TRACES_ENABLED	Enables traces.	true
OTEL_DOTNET_AUTO_OPENTRACING_ENABLED	Enables OpenTracing tracer.	false
OTEL_DOTNET_AUTO_LOGS_ENABLED	Enables logs.	true
OTEL_DOTNET_AUTO_METRICS_ENABLED	Enables metrics.	true
OTEL_DOTNET_AUTO_NETFX_REDIRECT_ENABLED	Enables automatic redirection of the assemblies used by the automatic instrumentation on the .NET Framework.	true
OTEL_DOTNET_AUTO_TRACES_ADDITIONAL_SOURCES	Comma-separated list of additional System.Diagnostics.ActivitySource names to be added to the tracer at the startup. Use it to capture manually instrumented spans.
OTEL_DOTNET_AUTO_TRACES_ADDITIONAL_LEGACY_SOURCES	Comma-separated list of additional legacy source names to be added to the tracer at the startup. Use it to capture System.Diagnostics.Activity objects created without using the System.Diagnostics.ActivitySource API.
OTEL_DOTNET_AUTO_FLUSH_ON_UNHANDLEDEXCEPTION	Controls whether the telemetry data is flushed when an AppDomain.UnhandledException event is raised. Set to true when you suspect that you are experiencing a problem with missing telemetry data and also experiencing unhandled exceptions.	false
OTEL_DOTNET_AUTO_METRICS_ADDITIONAL_SOURCES	Comma-separated list of additional System.Diagnostics.Metrics.Meter names to be added to the meter at the startup. Use it to capture manually instrumented spans.
OTEL_DOTNET_AUTO_PLUGINS	Colon-separated list of OTel SDK instrumentation plugin types, specified with the assembly-qualified name. Note: This list must be colon-separated because the type names may include commas. See more info on how to write plugins at plugins.md.

.NET CLR Profiler

The CLR uses the following environment variables to set up the profiler. See .NET Runtime Profiler Loading for more information.

.NET Framework environment variable	.NET environment variable	Description	Required value
COR_ENABLE_PROFILING	CORECLR_ENABLE_PROFILING	Enables the profiler.	1
COR_PROFILER	CORECLR_PROFILER	CLSID of the profiler.	{918728DD-259F-4A6A-AC2B-B85E1B658318}
COR_PROFILER_PATH	CORECLR_PROFILER_PATH	Path to the profiler.	$INSTALL_DIR/linux-x64/OpenTelemetry.AutoInstrumentation.Native.so for Linux glibc, $INSTALL_DIR/linux-musl-x64/OpenTelemetry.AutoInstrumentation.Native.so for Linux musl, $INSTALL_DIR/osx-x64/OpenTelemetry.AutoInstrumentation.Native.dylib for macOS
COR_PROFILER_PATH_32	CORECLR_PROFILER_PATH_32	Path to the 32-bit profiler. Bitness-specific paths take precedence over generic paths.	$INSTALL_DIR/win-x86/OpenTelemetry.AutoInstrumentation.Native.dll for Windows
COR_PROFILER_PATH_64	CORECLR_PROFILER_PATH_64	Path to the 64-bit profiler. Bitness-specific paths take precedence over generic paths.	$INSTALL_DIR/win-x64/OpenTelemetry.AutoInstrumentation.Native.dll for Windows

Setting OpenTelemetry .NET Automatic Instrumentation as a .NET CLR Profiler is required for .NET Framework.

On .NET, the .NET CLR Profiler is used only for bytecode instrumentation. If having just source instrumentation is acceptable, you can unset or remove the following environment variables:

COR_ENABLE_PROFILING
COR_PROFILER
COR_PROFILER_PATH_32
COR_PROFILER_PATH_64
CORECLR_ENABLE_PROFILING
CORECLR_PROFILER
CORECLR_PROFILER_PATH
CORECLR_PROFILER_PATH_32
CORECLR_PROFILER_PATH_64
OTEL_DOTNET_AUTO_INTEGRATIONS_FILE

.NET Runtime

On .NET it is required to set the DOTNET_STARTUP_HOOKS environment variable.

The DOTNET_ADDITIONAL_DEPS and DOTNET_SHARED_STORE environment variable are used to mitigate assembly version conflicts in .NET.

Environment variable	Required value
DOTNET_STARTUP_HOOKS	$INSTALL_DIR/net/OpenTelemetry.AutoInstrumentation.StartupHook.dll
DOTNET_ADDITIONAL_DEPS	$INSTALL_DIR/AdditionalDeps
DOTNET_SHARED_STORE	$INSTALL_DIR/store

Internal logs

The default directory paths for internal logs are:

• Windows: %ProgramData%\OpenTelemetry .NET AutoInstrumentation\logs
• Linux: /var/log/opentelemetry/dotnet
• macOS: /var/log/opentelemetry/dotnet

If the default log directories can't be created, the instrumentation uses the path of the current user's temporary folder instead.

Environment variable	Description	Default value
OTEL_DOTNET_AUTO_LOG_DIRECTORY	Directory of the .NET Tracer logs.	See the previous note on default paths
OTEL_DOTNET_AUTO_DEBUG	Enables debugging mode for the tracer.	false
OTEL_DOTNET_AUTO_TRACES_CONSOLE_EXPORTER_ENABLED	Whether the traces console exporter is enabled or not.	false
OTEL_DOTNET_AUTO_METRICS_CONSOLE_EXPORTER_ENABLED	Whether the metrics console exporter is enabled or not.	false
OTEL_DOTNET_AUTO_LOGS_CONSOLE_EXPORTER_ENABLED	Whether the logs console exporter is enabled or not.	false
OTEL_DOTNET_AUTO_LOGS_INCLUDE_FORMATTED_MESSAGE	Whether the log state should be formatted.	false