Docs » Analyze services with span tags and MetricSets in Splunk APM

Analyze services with span tags and MetricSets in Splunk APM 🔗

Use span tags to add additional context about the operations that spans represent, so that you can drill deeply into service performance.

Default span tags include attributes such as the endpoint, operation, and HTTP method associated with a span. You can also add custom span tags to include attributes of particular interest to you.

Using span tags, you can analyze requests, errors, and latency for spans that contain specific span tags. This context lets you understand service performance at a glance and helps you discover the root cause of issues faster.


Span tags are key-value pairs added to spans through instrumentation. In OpenTelemetry, these key-value pairs are known as attributes. See Add span tags with the Splunk Distribution of OpenTelemetry Collector to learn how to add span tags as attributes in the Splunk Distribution of OpenTelemetry Collector configuration YAML file.

Indexing span tags to generate MetricSets

By indexing span tags, you can generate MetricSets, which are metric time series of key indicators of service performance. For an overview of MetricSets in APM, see Learn about MetricSets in APM.

Indexing a span tag means APM automatically generates Troubleshooting MetricSets (TMS) with the span tag as a dimension. TMS are high cardinality metrics used for troubleshooting. You can also optionally generate Monitoring MetricSets, which are used for alerting and real-time monitoring. For an overview of MetricSets in APM, see Learn about MetricSets in APM.

Scenarios for indexed span tags and Troubleshooting MetricSets

Indexing span tags lets you analyze services in the following ways:

  • Break down service performance by indexed tags in the service map so that you can see which specific services attributes are associated with performance issues.

  • View charts of service performance metrics by indexed span tags in Tag Spotlight to discover relationships between specific span tag values and service behaviors.

  • Associate logically related spans so that you can track multiple traces for a specific activity using Business Workflows.

Analyze your services using span tags

Follow these steps to add, index, and start troubleshooting with span tags:

  1. Before you can index any span tags, you need to add span tags to the spans you send to APM. See Add context to spans with span tags in Splunk APM to learn how.

  2. To understand the benefits of indexing span tags and gaining MetricSets, see Learn about MetricSets in APM for an overview of the types of MetricSets available in APM.

  3. To learn how to index a span tag and generate Troubleshooting MetricSets, see Index span tags to generate Troubleshooting MetricSets.

  4. To learn how to generate Monitoring MetricSets, see Generate a Monitoring MetricSet with a custom dimension.

  5. To learn how to use Tag Spotlight, see Analyze service performance with Tag Spotlight.

  6. For details on how APM defines span tags and information to help you decide which span tags to index, see Reference and best practices for span tags and Troubleshooting MetricSets.

You can also download traces and filter or process data by span tags manually. To learn how to download a trace, see Download traces.


Your Splunk Observability Cloud contract may determine the number of span tags you can index to generate Troubleshooting MetricSets. If you choose not to index any additional span tags, you can still view tags in your spans when analyzing whole traces.