refactor(packetparser): reduce allocations in the hot path - #2508
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refactor(packetparser): reduce allocations in the hot path#2508Matthew McKeen (mmckeen) wants to merge 2 commits into
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The metrics dispatch and each metric module independently re-unmarshaled the flow's structpb extensions on every accessor call, so a single flow's extensions were decoded ~4-5 times across the forward/tcpflags/latency/dns/drops modules. Decode the extensions once in the dispatch loop and thread the *structpb.Struct through ProcessFlow, reading fields via new utils.*FromStruct accessors. The existing flow-based accessors delegate to these, so behavior is unchanged; only the redundant per-flow unmarshals are removed. Signed-off-by: Matthew McKeen <matthew.mckeen@fastly.com>
The conntrack GC loop logged every map entry (up to CT_MAP_SIZE) on each tick, and the cache IP lookup logged on every flow. Both built the zap field slice and formatted IPs/strings eagerly at the call site even when debug logging is disabled, allocating on the hottest paths in production. Guard both with logger.Check(zap.DebugLevel) so the field construction and formatting are skipped entirely unless debug logging is enabled. Signed-off-by: Matthew McKeen <matthew.mckeen@fastly.com>
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Description
Save some allocations by re-using the deserialized extensions struct in the hot path, also gate some debug only logs on log level where they are not needed.
Checklist
git commit -S -s ...). See this documentation on signing commits.Screenshots (if applicable) or Testing Completed
Deployed in test cluster, metrics are as before.
Please refer to the CONTRIBUTING.md file for more information on how to contribute to this project.