Datadog Plugin - Add path as tag

[fritzrichter]

Summary

It would be good to add the path as tag to the metrics in order to analyze and monitor individual API calls rather then aggregated metrics for the proxy.

Example

We have a service called auth-service and a route which maps everything below /auth/ to that upstream integration. We retrieve metrics for that routing, but I would like to understand metrics per path such as /auth/login and /auth/renew. Instead of creating a lot of different metrics, we would rather like to use tags for that purpose like "path=/login".