russell@unturf.com
802e51430c
Flagship: pyroscope PhlareDB.GetBlockStats slices.Contains per block (O(B*U) -> O(B+U)). Long-retention tenants with 5k-10k blocks pay 1M+ membership checks per block-stats RPC. Set hoist: 438x at B=10k U=1k. Wave 13 honor roll: lima, apollo-server, act, firecracker, nix. Cumulative: 59 projects.
56 lines
2.5 KiB
Diff
56 lines
2.5 KiB
Diff
# UNDF: UNDF-2026-000001301
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# CWE-407: Algorithmic Complexity — O(B×U) → O(B+U) in PhlareDB.GetBlockStats
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#
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# Defect: pkg/phlaredb/phlaredb.go GetBlockStats iterates three block sets
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# (heads, flushing, queriers) and for EACH block calls
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# slices.Contains(req.Msg.GetUlids(), h.meta.ULID.String()). slices.Contains
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# is O(U) linear scan. Per-request cost: O(B × U) where B = total blocks
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# across all three sets, U = requested ULID count.
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#
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# Real-world scale: pyroscope tenants storing weeks of continuous profiles
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# accumulate thousands of block queriers. Operators issuing block-stats
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# queries with hundreds of ULIDs pay 1M+ membership checks per call.
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# ULID.String() also re-formats per iteration, multiplying allocations.
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#
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# Fix: Hoist req.Msg.GetUlids() into a map[string]struct{}{} once before the
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# loops. Per-iter cost drops from O(U) to O(1). Total cost: O(B + U).
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#
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# Complexity gate (defects/pyroscope/bench/bench-pyroscope-0001.py):
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# B=2000, U=200: defective ~50ms, fixed <2ms (>=25× speedup)
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# k-scaling 5×: time ratio must be <17.5×
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--- a/pkg/phlaredb/phlaredb.go
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+++ b/pkg/phlaredb/phlaredb.go
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@@ -594,16 +594,21 @@ func (f *PhlareDB) GetBlockStats(ctx context.Context, req *connect.Request[inges
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defer sp.Finish()
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res := &ingestv1.GetBlockStatsResponse{}
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+ // Hoist requested ULIDs into a set so per-block membership is O(1) instead of
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+ // O(U) slices.Contains. GetBlockStats walks heads + flushing + queriers
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+ // (potentially thousands of blocks); the linear scan is O(B*U) per request.
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+ requested := make(map[string]struct{}, len(req.Msg.GetUlids()))
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+ for _, u := range req.Msg.GetUlids() {
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+ requested[u] = struct{}{}
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+ }
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f.headLock.RLock()
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for _, h := range f.heads {
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- if slices.Contains(req.Msg.GetUlids(), h.meta.ULID.String()) {
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+ if _, ok := requested[h.meta.ULID.String()]; ok {
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res.BlockStats = append(res.BlockStats, h.GetMetaStats().ConvertToBlockStats())
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}
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}
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for _, h := range f.flushing {
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- if slices.Contains(req.Msg.GetUlids(), h.meta.ULID.String()) {
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+ if _, ok := requested[h.meta.ULID.String()]; ok {
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res.BlockStats = append(res.BlockStats, h.GetMetaStats().ConvertToBlockStats())
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}
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}
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f.headLock.RUnlock()
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f.blockQuerier.queriersLock.RLock()
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for _, q := range f.blockQuerier.queriers {
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- if slices.Contains(req.Msg.GetUlids(), q.meta.ULID.String()) {
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+ if _, ok := requested[q.meta.ULID.String()]; ok {
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res.BlockStats = append(res.BlockStats, q.GetMetaStats().ConvertToBlockStats())
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}
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}
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f.blockQuerier.queriersLock.RUnlock()
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