[PROF-13950] ⚡️ Memoize getTimeZone to avoid repeated Intl.DateTimeFormat instantiation#4302
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thomasbertet wants to merge 2 commits intomainfrom
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[PROF-13950] ⚡️ Memoize getTimeZone to avoid repeated Intl.DateTimeFormat instantiation#4302thomasbertet wants to merge 2 commits intomainfrom
thomasbertet wants to merge 2 commits intomainfrom
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…rmat instantiation new Intl.DateTimeFormat() is expensive (locale negotiation + timezone resolution) and was called on every VIEW_UPDATED event. Since the timezone is static for the page lifetime, compute it once at module load time instead.
Switch from eager module-level computation to lazy caching: compute the timezone on first call and cache it, avoiding any cost at module load time.
Bundles Sizes Evolution
🚀 CPU PerformancePending... 🧠 Memory PerformancePending... |
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✅ Tests 🎉 All green!❄️ No new flaky tests detected 🎯 Code Coverage (details) 🔗 Commit SHA: 6b7b260 | Docs | Datadog PR Page | Was this helpful? React with 👍/👎 or give us feedback! |
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Motivation
new Intl.DateTimeFormat()can be an expensive browser API call (involves locale negotiation and timezone resolution). It was being executed on everyVIEW_UPDATEDlifecycle event viagetTimeZone()inprocessViewUpdate().VIEW_UPDATEDfires frequently: on every captured action, error, resource, long task, CLS/LCP/FCP update, context change, and more. Since the timezone never changes during a page session, this repeated work was pure waste.Related: PROF-13950
Identified while looking at some RUM Browser Profiler INP:
Changes
Memoize the timezone value at module load time in
packages/core/src/tools/utils/timezone.ts.resolveTimeZone()runs once, the result is stored in a module-level constant, andgetTimeZone()simply returns it.No behavior change — the returned value is identical.
Test instructions
No specific repro needed. Verify that
getTimeZone()still returns the correct timezone string in unit tests.Checklist