Customize Span Tags for RED Metrics | VMware Aria Operations for Applications Documentation

Customize span level tags for RED metrics

VMware Aria Operations for Applications (formerly known as Tanzu Observability by Wavefront) derives RED metrics for spans that have the application, service, cluster, shard, component, or operationName span tags by default. See Indexed and Unindexed Span Tags for details. If you want to filter RED metrics data using a span tag that is not a default span tag, you need to propagate it as a custom span tag to the RED metrics.

The following custom span tags are supported by default.

Custom span tag	Description
`span.kind`	Filter spans based on the span type. The default value is `none`. Example: `client` for a client-side span and `server` for a server-side span.
`http.status_code`	Filter spans based on the error code. Example: `404` or `500`

Follow the steps given below to propagate custom span tags when sending data from your application. Once the data is ingested, you can use queries to create custom dashboards that help you filter and view the information you need. Let’s look at a sample scenario that adds a custom span tag where you can compare the data in the production and staging environments.

Create a custom span-level tag. Assume you have a span that has the env= span tag.
Note:
When adding custom span-level tags, make sure that it is of low cardinality:
- Do not have more than 50 custom span tags.
- Do not have more than 100 values assigned to a span tag.
A tag with low cardinality has comparatively few unique values that are assigned to it.
If you are using OpenTelemetry, you send data to Operations for Applications using Wavefront proxy. Add the configuration shown below to the <wavefront_config_path>/wavefront.conf file. See Paths to find out where the file is saved.
```
traceDerivedCustomTagKeys=env
         
```
If you are using Jaeger, you send data to Operations for Applications using Wavefront proxy. Add the configuration shown below to the <wavefront_config_path>/wavefront.conf file. See Paths to find out where the file is saved.
```
traceDerivedCustomTagKeys=env
         
```
If you are using Zipkin, you send data to Operations for Applications using Wavefront proxy. Add the configuration shown below to the <wavefront_config_path>/wavefront.conf file. See Paths to find out where the file is saved.
```
traceDerivedCustomTagKeys=env
         
```
If your application uses Spring Boot 2, add the configuration shown below to your application's application.properties file.
```
wavefront.tracing.red-metrics-custom-tag-keys=env
         
```
If your application uses Spring Boot 3, add the configuration shown below to your application's application.properties file.
```
management.wavefront.trace-derived-custom-tag-keys=env
         
```
Add the configuration shown below to the <wavefront_config_path>/wavefront.conf file. See Paths to find out where the file is saved.
```
traceDerivedCustomTagKeys=env
         
```
Save the changes, restart the application, and start sending data.
Once the data is ingested, create a chart that compares the data sent by each environment. Here’s an example:
Note: You won’t see this data on the default service dashboard. If you want to customize the queries on the default service dashboard to see data from the custom span tags, you must clone and edit the dashboard.