feat: add default stats_tags to improve the prometheus metrics

[zirain]

xref: #7606

add default stats_tag config to improve the prometheus metric output.

• add rule for to_zone and from_zone

# TYPE envoy_sds_default_example_cert_init_fetch_timeout counter
envoy_cluster_zone_1__upstream_rq_time_count{envoy_cluster_name="tracing"} 12 # before
envoy_cluster_zone_upstream_rq_time_count{from_zone="1",envoy_cluster_name="default/tracing-datadog/default/backend"} 0 #after

• add rule for socket_match_name

# TYPE envoy_cluster_total_match_count counter
envoy_cluster_default_total_match_count{envoy_cluster_name="default/datadog-tracing"} 7 #before
envoy_cluster_total_match_count{socket_match_name="default",envoy_cluster_name="default/datadog-tracing"} 7 #after

• add rule for circuit breakers priority

# TYPE envoy_cluster_circuit_breakers_default_cx_open gauge
envoy_cluster_circuit_breakers_default_cx_open{envoy_cluster_name="default/datadog-tracing"} 0 #before
envoy_cluster_circuit_breakers_cx_open{priority="default",envoy_cluster_name="default/datadog-tracing"} 0 #after

Before:
before.txt

After:

after.txt

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 72.30%. Comparing base (b9123a8) to head (136dd59).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #7701      +/-   ##
==========================================
+ Coverage   72.28%   72.30%   +0.02%     
==========================================
  Files         234      234              
  Lines       34480    34480              
==========================================
+ Hits        24924    24931       +7     
+ Misses       7767     7760       -7     
  Partials     1789     1789              

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[jukie]

What would it look like for a user to opt-out from this? One consideration is that zone metrics are likely only relevant when using Zone Aware Routing and would only work if TopologyInjector is enabled (which is the default so not a huge deal).

[zirain]

that's something we need to figure out.
This PR made some breaking changes, which IMO it's good one, should be and a feature gate for this?

[jukie]

By breaking change you mean the metric name right? That doesn't seem too disruptive so as long as it's mentioned in the release notes I'm still okay with it.

Having this as the default seems reasonable so I don't think a feature gate is necessary. Users could modify the EnvoyProxy config to revert this if needed.

[zirain]

I'm 100% agree with you.

cc @envoyproxy/gateway-maintainers PTAL

[arkodg]

@zirain can you add a diff of before/after to the PR description, so its easier to understand the breaking stat changes

[zirain]

@zirain can you add a diff of before/after to the PR description, so its easier to understand the breaking stat changes

updated