[envoy] Missing Envoy metrics

Agent (v7.26.0)

A number of statistics from Envoyproxy are not exposed in Datadog. Amongst others these include the following:

https://www.envoyproxy.io/docs/envoy/latest/configuration/security/secret#statistics

https://www.envoyproxy.io/docs/envoy/latest/configuration/overview/extension#discovery-service

Steps to reproduce the issue:

1. Run Envoy with extension_config_discovery configuration
2. Enable Envoy integration in Datadog Agent
3. Double check in Envoy admin page that the following metrics are exposed:

http.*.extension_config_discovery.*.update_time
http.*.extension_config_discovery.*.version
sds.*.key_rotation_failed

Describe the results you received:

The above metrics are not available in any form in Datadog.

Describe the results you expected:

The above metrics are available, preferably with a tag for the specific sds name and extension_config_discovery name.

Additional information you deem important (e.g. issue happens only occasionally):

Would it be possible to interpret these metrics generically, so that with every new version of Envoy it would pick up such new metrics as well?

[HantingZhang2]

@bobvanderlinden Yes, however, since Envoy API v2 has been deprecated, we are adjusting our envoy test environment to adapt to v3 while keeping compatibility with v2.

[bobvanderlinden]

Thank you!