After you set up the tracing library with your code and configure the Agent to collect APM data, optionally configure the tracing library as desired, including setting up Unified Service Tagging.

You can set configuration settings in the .NET Tracer with any of the following methods:

using Datadog.Trace;
using Datadog.Trace.Configuration;

// read default configuration sources (env vars or datadog.json)
var settings = TracerSettings.FromDefaultSources();

// change some settings
settings.Environment = "prod";
settings.ServiceName = "MyService";
settings.ServiceVersion = "abc123";
settings.Exporter.AgentUri = new Uri("http://localhost:8126/");

// configure the global Tracer settings
Tracer.Configure(settings);

{
  "DD_TRACE_AGENT_URL": "http://localhost:8126",
  "DD_ENV": "prod",
  "DD_SERVICE": "MyService",
  "DD_VERSION": "abc123",
}

Configuration settings

Using the methods described above, customize your tracing configuration with the following variables. Use the environment variable name (for example, DD_TRACE_AGENT_URL) when setting environment variables or configuration files. Use the TracerSettings property (for example, Exporter.AgentUri) when changing settings in code.

Unified Service Tagging

To use Unified Service Tagging, configure the following settings for your services:

DD_ENV

TracerSettings property: Environment
If specified, adds the env tag with the specified value to all generated spans. Added in version 1.17.0.

DD_SERVICE

TracerSettings property: ServiceName
If specified, sets the service name. Otherwise, the .NET Tracer tries to determine service name automatically from the application name (IIS application name, process entry assembly, or process name). Added in version 1.17.0.

DD_VERSION

TracerSettings property: ServiceVersion
If specified, sets the version of the service. Added in version 1.17.0.

Optional configuration

The following configuration variables are available for both automatic and custom instrumentation:

DD_TRACE_AGENT_URL

TracerSettings property: Exporter.AgentUri
Sets the URL endpoint where traces are sent. Overrides DD_AGENT_HOST and DD_TRACE_AGENT_PORT if set. If the Agent configuration sets receiver_port or DD_APM_RECEIVER_PORT to something other than the default 8126, then DD_TRACE_AGENT_PORT or DD_TRACE_AGENT_URL must match it.
It can contain a Unix path to a socket by prefixing the path with unix://.
Default: http://<DD_AGENT_HOST>:<DD_TRACE_AGENT_PORT> if they are set, unix:///var/run/datadog/apm.socket if the file exists, or http://localhost:8126.

DD_AGENT_HOST

Sets the host where the Agent is listening for connections. Can be a hostname or an IP address. Use DD_TRACE_AGENT_URL, which has precedence over this parameter.
Default: localhost

DD_TRACE_AGENT_PORT

Sets the TCP port where the Agent is listening for connections. Use DD_TRACE_AGENT_URL, which has precedence over this parameter. If the Agent configuration sets receiver_port or DD_APM_RECEIVER_PORT to something other than the default 8126, then DD_TRACE_AGENT_PORT or DD_TRACE_AGENT_URL must match it.
Default: 8126

DD_TRACE_SAMPLE_RATE

TracerSettings property: GlobalSamplingRate
Default: Defaults to the rates returned by the Datadog Agent
Enables ingestion rate control. This parameter is a float representing the percentage of spans to sample. Valid values are from 0.0 to 1.0. For more information, see Ingestion Mechanisms.

Beta: Starting in version 2.35.0, if Agent Remote Configuration is enabled where this service runs, you can set DD_TRACE_SAMPLE_RATE in the Service Catalog UI.

DD_TRACE_SAMPLING_RULES

TracerSettings property: CustomSamplingRules
Default: null
A JSON array of objects. Each object must have a sample_rate. The name and service fields are optional. The sample_rate value must be between 0.0 and 1.0 (inclusive). Rules are applied in configured order to determine the trace’s sample rate. For more information, see Ingestion Mechanisms.
Examples:

• Set the sample rate to 20%: [{"sample_rate": 0.2}]
• Set the sample rate to 10% for services starting with ‘a’ and span name ‘b’ and set the sample rate to 20% for all other services: [{"service": "a.*", "name": "b", "sample_rate": 0.1}, {"sample_rate": 0.2}]

DD_TRACE_RATE_LIMIT

TracerSettings property: MaxTracesSubmittedPerSecond
The number of traces allowed to be submitted per second (deprecates DD_MAX_TRACES_PER_SECOND).
Default: 100 when DD_TRACE_SAMPLE_RATE is set. Otherwise, delegates rate limiting to the Datadog Agent.

DD_SPAN_SAMPLING_RULES

Default: null
A JSON array of objects. Rules are applied in configured order to determine the span’s sample rate. The sample_rate value must be between 0.0 and 1.0 (inclusive). For more information, see Ingestion Mechanisms.
Example: Set the span sample rate to 50% for the service my-service and operation name http.request, up to 50 traces per second: [{"service": "my-service", "name": "http.request", "sample_rate":0.5, "max_per_second": 50}]

DD_TRACE_DEBUG

Enables or disables debug logging. Valid values are true or false.
Default: false

DD_TRACE_HEADER_TAGS

TracerSettings property:HeaderTags
Accepts a map of case-insensitive header keys to tag names and automatically applies matching header values as tags on traces. Also accepts entries without a specified tag name that are automatically mapped to tags of the form http.request.headers.<header-name> and http.response.headers.<header-name> respectively.

Example (with specified tag names): User-ID:userId
If the Request has a header User-ID, its value is applied as tag userId to the spans produced by the service.

Example (without specified tag names): User-ID
If the Request has a header User-ID, its value is applied as tag http.request.headers.User-ID.
If the Response has a header User-ID, its value is applied as tag http.response.headers.User-ID.

Added in version 1.18.3.
Response header support and entries without tag names added in version 1.26.0.
Beta: Starting in version 2.35.0, if Agent Remote Configuration is enabled where this service runs, you can set DD_TRACE_HEADER_TAGS in the Service Catalog UI.

DD_TRACE_CLIENT_IP_ENABLED

Enables client IP collection from relevant IP headers.
Added in version 2.19.0.
Default: false

DD_TRACE_CLIENT_IP_HEADER

The IP header to be used for client IP collection, for example: x-forwarded-for.
Added in version 2.19.0.
Default: Datadog parses the following: x-forwarded-for, x-real-ip, true-client-ip, x-client-ip, x-forwarded, forwarded-for, x-cluster-client-ip, fastly-client-ip, cf-connecting-ip, cf-connecting-ipv6. If several are present, the first from the list to parse correctly will be used.

DD_TAGS

TracerSettings property: GlobalTags
If specified, adds all of the specified tags to all generated spans.
Example: layer:api, team:intake, key:value
Note: The delimiter is a comma and a space: , .
Added in version 1.17.0.

DD_TRACE_LOG_DIRECTORY

Sets the directory for .NET Tracer logs.
Default: %ProgramData%\Datadog .NET Tracer\logs\ on Windows, /var/log/datadog/dotnet on Linux

DD_TRACE_LOGFILE_RETENTION_DAYS

During the tracer’s startup, this configuration uses the tracer’s current log directory to delete log files the same age and older than the given number of days. Added in version 2.19.0.
Default: 31

DD_TRACE_LOGGING_RATE

Sets rate limiting for log messages. If set, unique log lines are written once per x seconds. For example, to log a given message once per 60 seconds, set to 60. Setting to 0 disables log rate limiting. Added in version 1.24.0. Disabled by default.

DD_TRACE_SERVICE_MAPPING

Rename services using configuration. Accepts a comma-separated list of key-value pairs of service name keys to rename, and the name to use instead, in the format [from-key]:[to-name].
Example: mysql:main-mysql-db, mongodb:offsite-mongodb-service
The from-key value is specific to the integration type, and should exclude the application name prefix. For example, to rename my-application-sql-server to main-db, use sql-server:main-db. Added in version 1.23.0

DD_HTTP_SERVER_TAG_QUERY_STRING

When set to true, the http.url includes query string parameters. You can find more details in Redacting the query in the url. Default: true

DD_HTTP_SERVER_TAG_QUERY_STRING_SIZE

When DD_HTTP_SERVER_TAG_QUERY_STRING is true, the max size of the querystring to report is set, before obfuscation. Set 0 for no limit in size
Default: 5000

DD_TRACE_OBFUSCATION_QUERY_STRING_REGEXP

When DD_HTTP_SERVER_TAG_QUERY_STRING is true, this regex redacts sensitive data from incoming requests’ query string reported in the http.url tag (matches are replaced with <redacted>). This regex executes for every incoming request.

DD_INSTRUMENTATION_TELEMETRY_ENABLED

Datadog may collect environmental and diagnostic information about your system to improve the product. When false, this telemetry data will not be collected.
Default: true

DD_TRACE_OTEL_ENABLED

Enables or disables OpenTelemetry based tracing, both for custom or automatic instrumentation. Valid values are: true or false.
Default: false

Automatic instrumentation optional configuration

The following configuration variables are available only when using automatic instrumentation:

DD_TRACE_ENABLED

TracerSettings property: TraceEnabled
Enables or disables all instrumentation. Valid values are: true or false.
Default: true Note: Setting the environment variable to false completely disables the client library, and it cannot be enabled through other configuration methods. If it is set to false through another configuration method (not an environment variable), the client library is still loaded, but traces will not be generated.

DD_DBM_PROPAGATION_MODE

Enables linking between data sent from APM and the Database Monitoring product when set to service or full. The service option enables the connection between DBM and APM services. The full option enables connection between database spans with database query events. Available for Postgres and MySQL.
Default: disabled

DD_HTTP_CLIENT_ERROR_STATUSES

Sets status code ranges that will cause HTTP client spans to be marked as errors.
Default: 400-499

DD_HTTP_SERVER_ERROR_STATUSES

Sets status code ranges that will cause HTTP server spans to be marked as errors.
Default: 500-599

DD_LOGS_INJECTION

TracerSettings property: LogsInjectionEnabled
Enables or disables automatic injection of correlation identifiers into application logs.
Your logger needs to have a source that sets the trace_id mapping correctly. The default source for .NET Applications, csharp, does this automatically. For more information, see correlated logs in the Trace ID panel.

Beta: Starting in version 2.35.0, if Agent Remote Configuration is enabled where this service runs, you can set DD_LOGS_INJECTION in the Service Catalog UI.

DD_RUNTIME_METRICS_ENABLED

Enables .NET runtime metrics. Valid values are true or false.
Default: false
Added in version 1.23.0.

DD_TRACE_EXPAND_ROUTE_TEMPLATES_ENABLED

Expands all route parameters in the application for ASP.NET/ASP.NET Core (except ID parameters)
This can be useful if you are using parameter names to differentiate between form values, or a slug, such as in GraphQL. Default: false Added in version 2.5.1.

DD_TRACE_METHODS

List of methods to trace. Accepts a semicolon (;) separated list where each entry has the format Namespace.TypeName[MethodNames], where MethodNames is either a comma (,) separated list of method names or the * wildcard. For generic types, replace the angled brackets and the type parameters’ names with a backtick (`) followed by the number of generic type parameters. For example, Dictionary<TKey, TValue> must be written as Dictionary`2. For generic methods, you only need to specify the method name.
Example: Namespace1.Class1[Method1,GenericMethod];Namespace1.GenericTypeWithOneTypeVariable`1[ExecuteAsync];Namespace2.Class2[*]
Note: The wildcard method support ([*]) selects all methods in a type except constructors, property getters and setters, Equals, Finalize, GetHashCode, and ToString.
Added in version 2.6.0. Wildcard support [*] added in version 2.7.0.

DD_TRACE_KAFKA_CREATE_CONSUMER_SCOPE_ENABLED

Alters the behavior of the Kafka consumer span
Default: true
When set to true, the consumer span is created when a message is consumed and closed before consuming the next message. The span duration is representative of the computation between one message consumption and the next. Use this setting when message consumption is performed in a loop.
When set to false, the consumer span is created when a message is consumed and immediately closed. Use this setting when a message is not processed completely before consuming the next one, or when multiple messages are consumed at once. When you set this parameter to false, consumer spans are closed right away. If you have child spans to trace, you must extract the context manually. Read Headers extraction and injection for more details.

Automatic instrumentation integration configuration

The following table lists configuration variables that are available only when using automatic instrumentation and can be set for each integration.

DD_DISABLED_INTEGRATIONS

TracerSettings property: DisabledIntegrationNames
Sets a list of integrations to disable. All other integrations remain enabled. If not set, all integrations are enabled. Supports multiple values separated with semicolons. Valid values are the integration names listed in the Integrations section.

DD_TRACE_<INTEGRATION_NAME>_ENABLED

TracerSettings property: Integrations[<INTEGRATION_NAME>].Enabled
Enables or disables a specific integration. Valid values are: true or false. Integration names are listed in the Integrations section.
Default: true

Experimental features

The following configuration variables are for features that are available for use but may change in future releases.

DD_TRACE_PARTIAL_FLUSH_ENABLED

Enables incrementally flushing large traces to the Datadog Agent, reducing the chance of rejection by the Agent. Use only when you have long-lived traces or traces with many spans. Valid values are true or false. Added in version 1.26.0, only compatible with the Datadog Agent 7.26.0+.
Default: false

Deprecated settings

DD_TRACE_LOG_PATH

Sets the path for the automatic instrumentation log file and determines the directory of all other .NET Tracer log files. Ignored if DD_TRACE_LOG_DIRECTORY is set.

DD_TRACE_ROUTE_TEMPLATE_RESOURCE_NAMES_ENABLED

Enables improved resource names for web spans when set to true. Uses route template information where available, adds an additional span for ASP.NET Core integrations, and enables additional tags. Added in version 1.26.0. Enabled by default in 2.0.0
Default: true

Further reading

Additional helpful documentation, links, and articles:

Connect .NET application logs to tracesDOCUMENTATION Runtime metricsDOCUMENTATION Propagating trace contextDOCUMENTATION Microsoft Azure App Service extensionDOCUMENTATION Explore your services, resources, and tracesDOCUMENTATION .NET monitoring with Datadog APM and distributed tracingBLOG Examples of custom instrumentationGITHUB Source codeGITHUB Deploy ASP.NET Core applications to Azure App ServiceBLOG