log: build on –vmodule downgrade work by replacing Clear() with atomic cache swap #33111
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jrhea
commented
Nov 6, 2025
| for _, rule := range curPatterns { | ||
| if rule.pattern.MatchString("+" + file) { | ||
| lvl, ok = rule.level, true | ||
| // TODO: Not breaking allows the last match to win. Is this what we want? |
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Builds on @MariusVanDerWijden’s original PR (#31536) to allow --vmodule log level downgrades by reworking the GlogHandler to use an atomic.Pointer[*sync.Map] for the callsite cache. I think this will eliminate Clear() races, avoid stale entry reinserts, and reduce lock contention while preserving the functionality introduced in Marius’s PR.
Key changes
• Replaced siteCache sync.Map with cachePtr atomic.Pointer[*sync.Map]
• Vmodule and Verbosity now atomically swap in a new cache instead of calling Clear()
• Updated WithAttrs to share the active cache pointer
Additional changes addressing original PR review feedback
• Handle snapshots h.patterns, performs regex matching outside the lock, and stores only if still current
• Simplified locking to a single sync.Mutex
• Forwarded the original ctx to origin.Handle(ctx, r)
⸻
Closes: #30717