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Open source

Tag search

An issue occurs while searching for traces in Grafana Explore. The Service Name and Span Name drop down lists are empty, and there is a No options found message.

HTTP requests to Tempo query frontend endpoint at /api/search/tag/ would respond with an empty set.

Root cause

The introduction of a cap on the size of tags causes this issue.

Configuration parameter max_bytes_per_tag_values_query causes the return of an empty result when a query exceeds the configured value.


There are two main solutions to this issue:

  • Reduce the cardinality of tags pushed to Tempo. Reducing the number of unique tag values will reduce the size returned by a tag search query.
  • Increase the max_bytes_per_tag_values_query parameter in the overrides block of your Tempo configuration to a value as high as 50MB.