feat: warn on dots in HTTPRoute names to avoid duplicate Prometheus series

[guanchzhou]

What this PR does

Sets a Warning status condition (reason DottedName) on an HTTPRoute when its name — or one of its rule names — contains a dot, signaling users to avoid dots in names.

Fixes #9576.

Why

Envoy derives Prometheus stat-tag labels by splitting cluster names on . (see the stats_tags regexes in the bootstrap). A cluster named httproute/<ns>/echo.a.example.com/rule/0 is therefore truncated at the first dot, so two HTTPRoutes sharing a before-first-dot prefix collapse to the same envoy_cluster_total_match_count{envoy_cluster_name="httproute/default/echo"} series. Being distinct counters, their values diverge and Prometheus rejects the samples (duplicate sample for timestamp), firing PrometheusDuplicateTimestamps.

Per the discussion, this implements the maintainer-preferred warning condition and intentionally does not rename/sanitize clusters or stat names (the dot→underscore AltStatName approach was declined).

Change

In processHTTPRouteParentRefs, after the Accepted condition is set, if the route name or any rule name contains a dot, add:

type: Warning
status: "True"
reason: DottedName
message: A dot in the HTTPRoute name or rule name(s) [...] causes Envoy to truncate
  Prometheus metric labels at the first dot, which can produce duplicate metric series;
  avoid dots in HTTPRoute and rule names.

• New custom RouteConditionWarning type + RouteReasonDottedName reason in internal/gatewayapi/status/error.go (mirrors the existing custom route-condition pattern and the PolicyConditionWarning precedent). There is no standard Gateway API route Warning type.
• The condition is set after the Accepted=True block so it doesn't suppress acceptance (that block only fires when no other condition is present).
• Scoped to HTTPRoute; GRPCRoute/TCP/TLS/UDP have the same dotted-name behavior and can be a follow-up.

Testing

• New golden pair internal/gatewayapi/testdata/httproute-with-dot-in-name.{in,out}.yaml — route named echo.a.example.com now carries the Warning/DottedName condition alongside Accepted/ResolvedRefs.
• No other goldens change (no existing fixture uses a dotted route name).

go build ./...                       # ok
go test ./internal/gatewayapi/...    # ok
make generate                        # clean (status string, no CRD/helm change)
gofmt -l / go vet                    # clean

Open question

Should this also cover GRPCRoute (and the L4 routes)? Happy to extend in this PR or a follow-up — whichever maintainers prefer.

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[codecov]

Codecov Report

❌ Patch coverage is 88.23529% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 76.08%. Comparing base (b710dd4) to head (ab39092).

Files with missing lines	Patch %	Lines
internal/gatewayapi/route.go	88.23%	1 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #9630      +/-   ##
==========================================
+ Coverage   76.04%   76.08%   +0.04%     
==========================================
  Files         259      259              
  Lines       43275    43292      +17     
==========================================
+ Hits        32907    32939      +32     
+ Misses       8178     8165      -13     
+ Partials     2190     2188       -2     

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