perf(mongodb): cache the per-connection topology shape#8370
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`wrapConnectionCommand` (mongodb >= 4) rebuilt the same five objects from `this.address` on every command. The Connection's address is immutable for its lifetime, so the work lands once on the first command and reuses a per-Connection envelope thereafter. The cache lives in a module-scope `WeakMap` instead of a Symbol-keyed property: the Connection is a foreign object, and an own-key (even a Symbol) shows up to `Reflect.ownKeys` / `Object.getOwnPropertySymbols`, forces a hidden-class transition on first hit, and can collide with another tracer's instrumentation walking the same connection. The extra `WeakMap.get` is single-digit nanoseconds and the foreign object stays untouched. The address parser tightens the previous `length === 2` split to "exactly one `:`, non-empty parts on both sides" so non-standard addresses (random UUIDs, IPv6 forms, empty port / host halves) all collapse to the empty-options topology. `synthesizeTopology` is exported so the parser is unit-tested directly rather than through the mongodb integration suite. Bench (Node 24.15 / V8 13.6, n=500 k x 7 trials, drop best+worst, warm cache, hit-only): per-command rebuild 19.30 ns/op cached envelope (WeakMap) 8.32 ns/op speedup: 2.32x
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Overall package sizeSelf size: 5.81 MB Dependency sizes| name | version | self size | total size | |------|---------|-----------|------------| | import-in-the-middle | 3.0.1 | 82.56 kB | 817.39 kB | | dc-polyfill | 0.1.11 | 25.74 kB | 25.74 kB |🤖 This report was automatically generated by heaviest-objects-in-the-universe |
🎉 All green!❄️ No new flaky tests detected 🎯 Code Coverage (details) 🔗 Commit SHA: ab6cee6 | Docs | Datadog PR Page | Give us feedback! |
BenchmarksBenchmark execution time: 2026-05-08 19:02:58 Comparing candidate commit ab6cee6 in PR branch Found 0 performance improvements and 0 performance regressions! Performance is the same for 1730 metrics, 114 unstable metrics. |
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`wrapConnectionCommand` (mongodb >= 4) rebuilt the same five objects from `this.address` on every command. The Connection's address is immutable for its lifetime, so the work lands once on the first command and reuses a per-Connection envelope thereafter. The cache lives in a module-scope `WeakMap` instead of a Symbol-keyed property: the Connection is a foreign object, and an own-key (even a Symbol) shows up to `Reflect.ownKeys` / `Object.getOwnPropertySymbols`, forces a hidden-class transition on first hit, and can collide with another tracer's instrumentation walking the same connection. The extra `WeakMap.get` is single-digit nanoseconds and the foreign object stays untouched. The address parser tightens the previous `length === 2` split to "exactly one `:`, non-empty parts on both sides" so non-standard addresses (random UUIDs, IPv6 forms, empty port / host halves) all collapse to the empty-options topology. `synthesizeTopology` is exported so the parser is unit-tested directly rather than through the mongodb integration suite. Bench (Node 24.15 / V8 13.6, n=500 k x 7 trials, drop best+worst, warm cache, hit-only): per-command rebuild 19.30 ns/op cached envelope (WeakMap) 8.32 ns/op speedup: 2.32x
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wrapConnectionCommand(mongodb >= 4) rebuilt the same five objects fromthis.addresson every command. The Connection's address is immutable for its lifetime, so the work lands once on the first command and reuses a per-Connection envelope thereafter.The cache lives in a module-scope
WeakMapinstead of a Symbol-keyed property: the Connection is a foreign object, and an own-key (even a Symbol) shows up toReflect.ownKeys/Object.getOwnPropertySymbols, forces a hidden-class transition on first hit, and can collide with another tracer's instrumentation walking the same connection. The extraWeakMap.getis single-digit nanoseconds and the foreign object stays untouched.The address parser tightens the previous
length === 2split to "exactly one:, non-empty parts on both sides" so non-standard addresses (random UUIDs, IPv6 forms, empty port / host halves) all collapse to the empty-options topology.synthesizeTopologyis exported so the parser is unit-tested directly rather than through the mongodb integration suite.Bench (Node 24.15 / V8 13.6, n=500 k x 7 trials, drop best+worst, warm cache, hit-only):
per-command rebuild 19.30 ns/op
cached envelope (WeakMap) 8.32 ns/op speedup: 2.32x