perf(metric): cache attribute-exclude filter decisions per key (mondaytweaks flag)#14
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…loop on every measurement Add CacheMetricAttributeExcludeDecisions flag (default true) in mondaytweaks. When enabled, both the Prometheus and OTEL attribute-filter closures use a sync.Map to memoize the regex-loop result per distinct attribute.Key. Attribute keys are a small, bounded, static set, so after warmup the hot path is a single map lookup (O(1), zero regex calls). Benchmarks (15 keys, 3 regexes, Apple M4 Pro): OTEL old: 1320 ns/op, 0 B/op, 0 allocs → new: 145 ns/op, 0 B/op, 0 allocs (~9x) Prom old: 2130 ns/op, 350 B/op, 15 allocs → new: 152 ns/op, 0 B/op, 0 allocs (~14x, all allocs eliminated) Semantics are identical: same regexes, same inputs, result cached per key.
Router image scan passed✅ No security vulnerabilities found in image: |
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What
Caches the attribute-exclude filter decision for each attribute key so the regex loop runs once per unique key rather than on every metric measurement.
Without caching, every call to
AddCustomMetricAttributesiterates over all exclusion patterns for every attribute it receives — at high metric throughput this shows up as a measurable hot path. A 2026-07-10 production pprof analysis (12:00–12:05 UTC, 3 regions) confirmed the OTEL regex exclude filter at 4.4% CPU + 16.5 GB alloc/90 s.New mondaytweaks flag
CacheMetricAttributeExcludeDecisionsBenchmarks
Measured with
go test -bench=BenchmarkMetricAttributeExclude -benchmem -count=5on the same machine before and after the change.Before
After
~9× faster for OTEL, ~14× faster for Prometheus; Prometheus allocations eliminated.
Source
Derives from the 2026-07-10 production pprof analysis of the Cosmo router.