There are currently a few server side options that can be set to limit the impact of tag and tag value queries:

max_bytes_per_tag_values_query
max_blocks_per_tag_values_query

However, it's likely a user of Tempo may want to purposefully limit the number of tags returned on large queries. Let's add a query parameter allowing the caller of Tempo to indicate the maximum number of results they would like to see.

/api/v2/searc/tags?limit=<int>
/api/v2/search/tag/<tag>/values?limit=<int>