feat: add Go benchmarks for reconciliation hot paths

[maksymvavilov]

Summary

Go benchmarks for reconciliation hot paths with a CI workflow that posts benchstat comparisons on PRs. 11 benchmark functions, 40 sub-benchmarks, ~10.7 min total runtime.

Benchmarks

All benchmarks use the bench build tag (//go:build bench), fully decoupled from unit tests.

Benchmark	What it measures	Sub-benchmarks
CalculateEffectiveAuthPolicies	O(GC×RouteRules) Paths() loop	10, 100, 300 routes; 3gc×100
EffectiveRateLimitPolicies	RLP effective policy calculation	10, 100, 300 routes
EffectiveAuthPoliciesListenerFanout	Listener scaling impact on Paths() DFS	1, 4, 16, 32 listeners
EffectiveAuthPoliciesMultiGateway	Multi-gateway with distributed routes	3gc, 10gc
TopologyToDot	DAG-to-DOT serialization (called every cycle)	10, 100, 300, 1000 objects
BuildDesiredAuthConfig	AuthConfig generation per route rule	1, 10, 100, 300 rules
BuildLimitadorLimits	Merging effective policies into Limitador limits	10, 100, 300 policies
TopologyPaths	Isolated Paths() DFS traversal	narrow, wide, deep, stress
GetKuadrantFromTopology	Kuadrant CR lookup cost (~28 calls/cycle)	10, 100, 300 routes
TopologyBuild	Cost of constructing the topology	10–300 routes; 32L, 3gc×16L
FullReconciliationCycle	Topology build + lookups + all 3 reconcilers	10, 100, 300 routes

Running

# Full suite (10 repetitions for benchstat)
make test-bench

# Single benchmark
go test ./internal/controller/... -bench=BenchmarkTopologyPaths -benchmem -run='^$' -count=1 -tags bench

# Compare before/after with benchstat
benchstat before.txt after.txt

CI Workflow

.github/workflows/benchmark.yaml runs on PRs touching internal/, pkg/, api/, go.mod:

• Runs benchmarks on both PR and base branch (-count=10)
• Posts benchstat comparison as a sticky PR comment
• Inform-only — does not fail the build
• Uploads raw results as artifacts

Credits

Scaling benchmarks (listener fanout, multi-gateway, RLP, topology build, full cycle) adapted from Mike Nairn's PR #2031.

🤖 Generated with Claude Code

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