Allow setting numbers as tags

[felixbarny]

Having the ability to set custom number values which are indexed in Elasticsearch allows to create aggregated graphs based on transactions.

For example, you could track the number of search results for a search transaction, along with the search query to get a list of the top searches without results.

[simitt]

Do you mean something similar as marks, which can be nested objects with number values?

This wouldn't be a big issue from a technical point of view (except for the one open issue that we also have with marks #708).

[felixbarny]

Yes, similar to marks, but mark values should always be a timestamp in ms, right? Shouldn't we map it to a date then?

For this, we should pre-define a mapping so that we don't have the issue mentioned in #708. Double would be the most flexible datatype for this I guess.

[simitt]

Are you considering nested objects with double values, or a flat hierarchy as for tags?

[felixbarny]

Just flat key value pairs with double values

[alvarolobato]

@felixbarny is this related to Open Tracing?

[felixbarny]

OpenTracing allows to set string, boolean and number tags. Converting the numbers to strings does not really break the contract, but it means the users can't create graphs based on the number tags.

Example: the user could add a tag to a checkout cart span which represents the total value of the cart. If we don't support number tags, the user can't create a Kibana visualization with graphs the revenue.