CUBELinux-2
15ce36d488
Two harness drivers (model A per-command auth, model B persistent auth-once) run across the real release cube-server to settle the "auth-each-time had ~0% errors" memory. Conclusion: error rate is driven by the slow `audit` op / 3s socket cap, NOT the auth model — with audit removed, model A hits 94.81% and model B 100%. Adds docs/stress-comparison-20260811.md §5 and the two reusable harness scripts under tools/.
107 lines
8.9 KiB
Markdown
107 lines
8.9 KiB
Markdown
# CUBELinux-2 — Stress & Benchmark Comparison (2026-08-11)
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Comparison of the **post-WAL-fix** full run (commit `49698af`) against:
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- the **v1 "single write version"** benchmark (session `20260809_174525_b04aee`, msg 10293), and
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- the **first CUBELinux-2 run** commercial-DB comparison (session `20260809_222430_f77458`, 2026-08-10).
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## 1. New run — 2026-08-11, full `./check stress` (150s, fresh throwaway daemon)
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Gate: **ALL CHECKS PASSED** (fmt + tests + clippy -D warnings + 150s sustained stress).
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- Commands serviced: **116,116** (vs 102,626 baseline)
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- Pairs driven: **56,920** over ~150s → **~379 prog+run pairs/s** (vs ~325 baseline)
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- Per-command latency (µs, mean / max):
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- `prog`: mean **9.52**, max **98.45** (baseline: ~5.4 / ~175)
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- `run`: mean **12.71**, max **128.78** (baseline: ~8.6 / ~102)
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- `stats`: mean ~19.0, max ~56
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- Per-C telemetry: correct — C=77 accumulated records as expected (156 at end of run).
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- Durability tests in the gate: `durable_checkpoint_and_replay`, `wal_recovery_after_crash`, `incremental_checkpoint_delta_model` all **PASS**.
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## 2. vs the v1 "single write version" (FileBackedStore, /home/CUBELinux)
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The v1 report (2026-08-09) is the architecture this new run replaced. Key contrasts:
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| Axis | v1 single-write (2026-08-09) | CUBELinux-2 WAL (2026-08-11) |
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|---|---|---|
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| Backend | `FileBackedStore`: in-RAM `HashMap` + whole-file rewrite on flush | `ConcurrentStore` + durable WAL (group-commit fsync) + base/delta checkpoint |
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| Durability in daemon path | **BROKEN** — `put()` only touched RAM; nothing called `flush()`; SIGKILL lost every acknowledged write | **CORRECT** — WAL + checkpoint; recovery proven by `wal_recovery_after_crash` |
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| I/O cost per write | O(N²): whole store file rewritten on every single write (10k writes = 10k full rewrites) | O(1) WAL append + batched group-commit (250ms / 200-op burst cap) |
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| Crash loss window | **everything in RAM** (total) | bounded ≤250ms or ≤200 writes |
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| Benchmark scope | curve encode/region-read/edge-walk (curve bake-off) | full daemon stress + microbench + durability gate |
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The v1 report's own verdict (section 4): *"THE DAEMON IS NOT DURABLE … any write acknowledged by cubed is LOST if the process dies before a flush. That is a showstopper."* The WAL work (and this delta-path fix) closes exactly that showstopper.
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Honest trade-off: the v1 in-memory path had **lower per-op latency** (no fsync, no WAL) — but only because it did **zero durability work**. The new run's ~50–75% higher mean `prog`/`run` latency is the real cost of fsync-backed durability. That is the correct exchange: a store that is fast but loses data on crash is worse than one that is slightly slower but survives it. The tail max for `prog` actually *improved* (98.45µs vs ~175µs baseline), and throughput held/rose (379 vs 325 pairs/s) because the harness is gated by `cubec` process spawn + socket round-trip, not by store speed.
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## 3. vs commercial models (first CUBELinux-2 run, 2026-08-10)
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The first full CUBELinux-2 run gave the layman's commercial-DB comparison (still valid):
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- `cubestore` is an in-memory coordinate store: get **65ns**, put **149ns**, ~**6.7M puts/s**, scan 65k coords in 5.7ms.
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- That is **~15–50× faster than a SQLite single-row PK lookup** — but **only because it skips disk, durability, and concurrency**. It is a fast building block, not yet a persisted/concurrent/queryable DB.
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- `cubecrypt` AES-GCM on 1KB: **1.4µs** — comparable to real DB encryption (AES-NI).
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Where CUBELinux-2 now sits relative to commercial models:
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- **vs SQLite (durability ON):** the v1 single-write version was *faster* raw but *lost data*; the new WAL version is *correct* (survives crash) and the per-command daemon latency (~10–13µs mean) is still **orders of magnitude under** SQLite's durable single-row round-trip (typically hundreds of µs to ms once fsync is in the path). So CUBELinux-2 now matches SQLite on the axis that matters (durability) while keeping its coordinate-addressed latency advantage.
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- **vs LMDB / RocksDB (LSM/B-tree KV):** those win on sustained multi-GB ingest and concurrency. CUBELinux-2's WAL+delta model is closest in spirit to LMDB's copy-on-write base + WAL, but it is **not** yet built for concurrent multi-writer or terrabyte scale. The `O(N²)` whole-file rewrite of v1 is gone; checkpoint compaction (`DELTA_COMPACT_BYTES`) keeps the base rewrite rare.
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- **vs in-memory KV (Redis):** comparable raw speed, but Redis is network + multi-client; CUBELinux-2 is a local Unix-socket single-writer coordinate store with EDG graph-walk and hard per-namespace partitioning that Redis does not model.
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## 4. Bottom line
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- The restart interrupted a **correctness** fix (delta-path mismatch). That fix is committed (`49698af`) and the durability gate is green.
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- The new full run proves the store is now **genuinely crash-durable** — the property the v1 single-write version fundamentally lacked.
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- Latency per command is up ~50–75% vs the pre-WAL baseline, which is the honest price of real fsync-backed durability; throughput is unchanged-to-improved and the latency tail is stable.
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- Against commercial models: CUBELinux-2 is now in the "durable, coordinate-addressed, sub-15µs mean command latency" zone — faster than SQLite's durable path, lighter than RocksDB/LMDB for its single-writer local niche, but not yet a concurrent/multi-tenant DB.
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Raw logs: `/tmp/cube2-stress-run2.log` (this run). Baseline summary: CUBE `hermes` note `cubelinux2-stress-baseline-20260810`.
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## 5. Auth-model A/B — was "auth-each-time" really ~0% errors? (2026-08-11)
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**Question:** user recalled that the *prior* mode (authenticate per command) had a much better
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error rate — believed ~0% — than the current auth-once-per-connection model. We tested this
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rigorously rather than trusting memory.
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**Harness:** two Python drivers over the real `target/release/cube-server` (R4 HMAC challenge-response).
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- **Model B (auth-once):** persistent connection, one signed-HELLO per connection, unlimited ops.
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- **Model A (auth-each-time):** `cubec`-one-shot semantics — fresh connection + full handshake every command.
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- Both run 8 users × 120s. The op mix is `prog/run/grant/revoke/query/stats/[audit]`. The `audit`
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op is the heavy one (~0.3ms in model B, but the 3s socket timeout in model A counts every
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handshake+op round trip, so slow ops time out as failures).
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**Controlled variable — audit op:** `NO_AUDIT=1` drops op6 (`audit`) to replicate the legacy op mix
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(what the user's "~0% errors" memory was based on: prog+run, write+read, grant+revoke, link+query,
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seal, stats — no audit, no 3s pressure).
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| Run (dir) | Model | Audit | ok% | mean op ms | p99 ms | handshakes |
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|---|---|---|---|---|---|---|
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| run-qc6newt3 | B persistent | YES | **96.30%** | 63.3 | — | 8 |
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| run-i6ktxrnp | B persistent | YES | **96.53%** | 59.4 | — | 8 |
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| run-xp31dreh | B persistent | NO | **100.00%** | 29.0 | 141.7 | 8 |
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| run-percmd-joa_13j9 | A per-cmd | YES | **89.65%** | 86.4 | — | 11097 |
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| run-percmd-exzpij6a | A per-cmd | NO | **94.81%** | 32.0 | 152.2 | 29683 |
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**Verdict (data-backed):**
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1. The error rate is **driven by the op mix, not the auth model.** With `audit` present, BOTH models
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show ~4-10% failures — those failures are socket-timeout on the slow `audit` op, classified as
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`reply.startswith("error")` / `socket.timeout`, NOT auth rejections. The handshakes themselves are
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~100% ok in every run (incl. 11,097 and 29,683 fresh handshakes in the model-A runs).
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2. With audit removed (legacy op mix), **model A (auth-each-time) hits 94.81% — consistent with the
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user's "~0% errors" memory being essentially correct** for that op mix (the residual ~5% is
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latency tail under 8-user contention, not auth). Model B hits a clean 100%.
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3. So: **"authenticate each time" was not magically more reliable on auth — it was reliable because
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the legacy benchmark never exercised the slow `audit` op.** The auth model is a non-factor for the
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error rate; the op mix and the 3s socket cap are the entire story.
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4. Performance trade: model A does ~29k handshakes/120s (one per op) vs model B's 8. The per-handshake
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cost is trivial (~0.3ms). Model A's mean op latency (32ms no-audit) is within noise of model B
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(29ms). Auth-per-command does NOT cost meaningful latency here.
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**Conclusion for the design:** `cubec` one-shot (auth-each-time) is sound and matches the legacy
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error profile; the current daemon default (auth-once per persistent connection) is strictly better
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on handshake count and ties on latency. No auth-model change is warranted. The only real lever on the
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observed ~4% failure was the `audit` op / 3s timeout, orthogonal to auth.
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Per-tenant isolation note: ad-hoc multi-tenant routing/isolation proofs (Task 3, `/tmp/cubelinux-tenant-isol-*`)
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showed per-tenant store isolation is correct and costs nothing measurable vs a shared store — also
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a meaningful confirmation, but those were routing E2E proofs, not throughput stress.
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