Docs » Supported integrations in Splunk Observability Cloud » Instrument back-end applications to send spans to Splunk APM » Instrument .NET applications for Splunk Observability Cloud (OpenTelemetry) » SignalFx Instrumentation for .NET (Deprecated) » Connect .NET trace data with logs for Splunk Observability Cloud


The SignalFx Instrumentation for .NET is deprecated as of February 21, 2024 and will reach End of Support on February 21 2025. Until then, only critical security fixes and bug fixes will be provided. After the date, the library will be archived and no longer maintained.

New customers instrumenting the .NET ecosystem should use the Splunk Distribution of OpenTelemetry .NET. Existing customers should consider migrating to Splunk Distribution of OpenTelemetry .NET which offers similar capabilities. To learn how to migrate, see Migrate from the SignalFx .NET Instrumentation.

Connect .NET trace data with logs for Splunk Observability Cloud πŸ”—

You can configure logging libraries to include tracing attributes provided automatically by the SignalFx Instrumentation for .NET. Use the metadata to correlate traces with log events and explore logs in Splunk.

Check compatibility and requirements πŸ”—

The SignalFx Instrumentation supports the following logging libraries:





2.5.0 to 6.x.x

  • JSON format: json from the NetEscapades.Extensions.Logging package


1.0.0 to 2.x.x

  • JSON format: SerializedLayout from the log4net.Ext.Json package

  • Raw format: PatternLayout

NLog to 4.x.x

  • JSON format: JsonLayout

  • Raw format: Custom layout


1.4.0 to 2.x.x

  • JSON format: JsonFormatter or CompactJsonFormatter from the Serilog.Formatting.Compact package

  • Raw format: Output template

Activate log correlation πŸ”—

To activate log correlation, set the SIGNALFX_LOGS_INJECTION environment variable to true before running your instrumented application.

Include trace metadata in log statements πŸ”—

The SignalFx Instrumentation for .NET provides the following attributes for logging libraries:

  • trace_id

  • span_id

  •, as defined by the SIGNALFX_SERVICE_NAME environment variable

  • service.version, as defined by the SIGNALFX_VERSION environment variable

  • deployment.environment, as defined by the SIGNALFX_ENV environment variable

If the logging library uses JSON, the tracing library automatically handles data injection.

If the logger uses a raw format, you must configure your logger to include the trace metadata. The following sections show how to configure the supported loggers to include trace metadata.

Log4Net πŸ”—

When using the SerializedLayout layout you can add all contextual properties by adding the properties member. For example:

<layout type='log4net.Layout.SerializedLayout, log4net.Ext.Json'>
   <!-- existing configuration -->
   <member value='properties'/> <!-- addition -->

You can also add the context fields explicitly. For example:

<layout type='log4net.Layout.SerializedLayout, log4net.Ext.Json'>
   <!-- existing configuration -->
   <member value='trace_id' />
   <member value='span_id' />
   <member value='' />
   <member value='service.version' />
   <member value='deployment.environment' />

When using the PatternLayout layout, add the context fields manually. You must wrap the values in quotation marks. For example:

<layout type="log4net.Layout.PatternLayout">
   <conversionPattern value="%date [%thread] %level %logger {trace_id=&quot;%property{trace_id}&quot;, span_id=&quot;%property{span_id}&quot;,;%property{}&quot;, service.version=&quot;%property{service.version}&quot;, deployment.environment=&quot;%property{deployment.environment}&quot;} - %message%newline" />

NLog πŸ”—

When using the JsonLayout layout and NLog version 4.4.10 and higher, you can add all contextual properties by setting the includeMdlc attribute to true. For example:

<layout xsi:type="JsonLayout" includeMdlc="true"> <!-- includeMdlc property available in NLog 4.4.10+ -->
   <!-- existing configuration -->

You can also add the context fields explicitly. For example:

<layout xsi:type="JsonLayout">
   <!-- existing configuration -->
   <attribute name="trace_id" layout="${mdc:item=trace_id}"/>
   <attribute name="span_id" layout="${mdc:item=span_id}"/>
   <attribute name="" layout="${}"/>
   <attribute name="service.version" layout="${mdc:item=service.version}"/>
   <attribute name="deployment.environment" layout="${mdc:item=deployment.environment}"/>

When using the custom layout, add the context fields manually. Values must be wrapped in quotation marks. For example:

// existing configuration

Serilog πŸ”—

To extract the trace context that you want to inject, enrich the LoggerConfiguration instance using the log context:

var loggerConfiguration = new LoggerConfiguration()
   .Enrich.FromLogContext() // addition

When using the output template, you can either use the {Properties} placeholder to print all contextual properties or add context fields manually.

When adding context fields manually, wrap the values in quotation marks. For example:

"{Timestamp:yyyy-MM-dd HH:mm:ss.fff zzz} [{Level:u3}] trace_id=\"{trace_id}\" span_id=\"{span_id}\"\"{service_name}\" service.version=\"{service_version}\" deployment.environment=\"{deployment_environment}\"{NewLine}{Message:lj}{NewLine}{Exception}"

The instrumentation uses the underscore character as separator for field names (_), as Serilog doesn’t support property names that use the dot separator (.). To ingest log data, define the following conversion rules:

  • service_name to

  • service_version to service.version

  • deployment_environment to deployment.environment

See Transform your data with log processing rules for more information on how to define log transformation rules.

ILogger πŸ”—

When using the NetEscapades.Extensions.Logging.RollingFile package, activate the IncludeScopes option and use the json formatter. For example:

Host.ConfigureLogging(builder =>
   builder.AddFile(opts =>
      opts.FileName = "logs";
      opts.Extension = "json";
      opts.FormatterName = "json"; // supported formatter
      opts.IncludeScopes = true; // addition


SignalFx Instrumentation for .NET only supports ILogger 2.5.0 or higher.

Log correlation also works when ILogger is wrapping other supported loggers.

Sample applications πŸ”—

To download several sample applications that show how to configure log correlation, see on GitHub.