Missing istio/envoy Lua filter metrics

[jwillker]

We have an Envoy and Istio integration configured, and everything is fine and working. we also have an Istio configuration to include some envoy metrics, but the Lua filter doesn't work.

Example:

    defaultConfig:
      proxyStatsMatcher:
        inclusionRegexps:
          - ".*http_local_rate_limiter.*"
          - ".*lua_filter.*"

The metric envoy.http.local_rate_limit_enabled.count appears in the datadog but the envoy_http_lua_<PREFIX>_errors, that by my config the prefix is "lua_filter", the metric should be envoy_http_lua_lua_filter_errors.

The missing metric is present in the open metrics endpoint: http://%%host%%:15090/stats/prometheus"

Maybe the Datadog is not expecting any metric from Lua filters.

Lua filter doc: https://www.envoyproxy.io/docs/envoy/latest/api-v3/extensions/filters/http/lua/v3/lua.proto#envoy-v3-api-field-extensions-filters-http-lua-v3-lua-stat-prefix

This is very important to have this metric in datadog.