shoney.arickathil
58dcb1f969
- residency-accept.sh section 8 (11 checks): file-form seed -> restart prints
the directory form's line; `find -mindepth 1` shows exactly app.db; missing
parent exits 2 naming path + parent, no mkdir -p; a fifo exits 2 "neither a
regular file nor a directory"; `d/` still writes d/shard-0.wal; `nodir/`
keeps the pre-7 "cannot open .../nodir//shard-0.wal" bytes; WO_EPHEMERAL=1
with the file exits 2 on the 6a conflict
- kill -9 battery against app.db: stdbuf -oL vehicle, asserts the kill landed
(rc 137) before verifying every acked row replays; forced compaction
(WO_CHECKPOINT_BYTES=1, WO_WAL_STATS proves >= 1 ran) leaves app.db the only
artifact and every row replays
- failing-first on the pre-7 wovm: 9 of 12 new checks red ("cannot open
.../app.db/shard-0.wal"); the two trailing-slash pins and the 6a conflict
pass by construction — they pin what must stay byte-identical
- db-bench.py --wo-data-file: restart proof + crash battery against
<tmp>/app.db, legs tagged .file, file form also asserts app.db is the only
artifact; no metric, bench/baseline.json untouched; quick run unchanged
without the flag (181 checks / 5 failures both ways, all five the known
residency.keys.fit rc 74)
- READMEs: db-bench env-knob row for WO_DATA=<path>.db + the driver flag;
residency run instructions name the file form
- gates: just residency 32/1 (the seed rc, pre-existing), make -C runtime
test 21 suites 8452/0, just oop-e2e 129/0
Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
(cherry picked from commit aaea6b2c0f818efd0cdf472ccbd9bdd09eac5554)
86 lines
6.2 KiB
Markdown
86 lines
6.2 KiB
Markdown
# db-bench — iteration 22's load generator
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The measurement backbone (spec:
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`docs/superpowers/specs/2026-08-21-db-bench-design.md`). Pure `.wo`;
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every measured mode prints one machine-parsable line per operation
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class:
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<op> <count> <ops/sec> <p50us> <p99us>
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Timing is per-operation via `time.ticks` (CLOCK_MONOTONIC µs).
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Percentiles come from a 1µs-bucket histogram clamped at 20000µs — exact
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to the microsecond below the clamp; a p99 AT 20000 means "clamp or
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worse". (A histogram, not the spec's reservoir: the language has no
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container element-write or sort, and the histogram's tail fidelity is
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strictly better. Recorded as a plan deviation.)
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## Modes
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| mode | what it prices |
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| --- | --- |
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| `all N` | the throughput campaign in ONE process: seed N, read N/2, query N/10, write N/2. Without `WO_DATA` the store is RAM and dies with the process, so the measured modes must share the seeding run. |
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| `seed N` | timed inserts: one parent per 100 children (FK probe each insert, unique-index maintenance per parent), k non-unique (10 rows/key), deterministic v. Writes `Meta` expectation rows. |
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| `read N` | indexed take-1 point lookups, LCG-spread keys. |
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| `query N` | full equality probes on the k index (≈10 rows each), materialized and counted. |
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| `write N` | alternating inserts (disjoint k range 2e6+) and updates through query results. Corrupts the checksum by design — durability legs run on a fresh store. |
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| `wal N` | the crash battery's vehicle: insert-only (k range 1e6+), `acked <i>` printed AFTER each insert returns — the return IS the ack (RAM applied, WAL record staged, ONE commit done). |
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| `wmix N C` | **databasev2 4:** every op a durable write (update through a query result), C at once. Exists because `mix` writes on one op in ten with C=4 — 20 writes in a quick run, measured mean batch **1.01** — so no existing leg could show whether group commit engages. Histogram kind 2, because a replayed store still holds the seeding run's kind-0/1 `Hist` rows. Seed first. |
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| `boot` | **databasev2 3:** does NOTHING. With `WO_DATA` set the runtime replays the whole log before `main` runs, so a mode with no work of its own is the only honest way to price boot |
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| `verify` | store vs its own Meta rows: count, checksum, one unique probe. Exit 3 on mismatch. |
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| `verify-acked M` | after kill -9 mid-`wal`: rows 1..M exist with the right v; rows beyond M allowed (acked after the last print flushed). Exit 3 on mismatch. |
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## Env knobs
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| var | effect |
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| --- | --- |
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| `WO_DATA=<dir>` | durability on: replay `<dir>/shard-0.wal` at boot, log every write. Without it the store is RAM-only |
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| `WO_SHARDS=<n>` | shard count. **`1` means every statement runs inline on shard 0 and group commit cannot engage** — batches form only where writes queue from other shards |
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| `WO_CHECKPOINT_BYTES` / `WO_CHECKPOINT_RATIO` | **databasev2 3:** the checkpoint trigger — the log must exceed the floor AND exceed the ratio times the last compaction's own size. A tiny floor forces compaction in a few writes, which is how the gate tests the policy at all; an enormous one disables it, which is how the checkpoint leg measures the same workload with and without |
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| `WO_WAL_STATS=1` | **databasev2 4:** print one line at exit — `walstats batches=… records=… peak_batch=… peak_staged=… compactions=… compact_us_max=… compact_us_total=… compacted_bytes=…`. Opt-in so it does not pollute every durable program's output. Mean batch is `records/batches`; **mean 1.0 means group commit is not engaging**, which is expected for a serial writer or `WO_SHARDS=1` and a bug anywhere else |
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| `WO_DATA=<path>.db` | **databasev2 7:** the store as ONE file — the path IS the log (created if absent, its parent must exist; a directory or trailing `/` keeps the `<dir>/shard-0.wal` form). `scripts/db-bench.py --wo-data-file` runs the restart proof and the kill -9 battery against `<tmp>/app.db` instead of a directory; same acceptance, no metric, baseline untouched |
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**Do not put `WO_DATA` on `/tmp`.** It is `tmpfs` on the reference machine,
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where `fdatasync` is free: the same `wmix` run measured **195 000 ops/s at p50
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1 µs** there against **2200 ops/s at p50 7200 µs** on ext4. There is no
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durability barrier to price on a memory filesystem. The driver keeps its stores
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under `bench/` for exactly this reason.
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## Coordination idiom (this side of iteration 31)
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There is no request/response surface yet: concurrent modes drive
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completion the db-actor way — actors write rows, main polls the store
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until the expected count, then settles. Retired when 31 lands.
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## Standing finding (2026-08-21, first run)
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A hand-built `multi Bucket` of insert results SEGVs on drop: the
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compiler classifies the elements OWNED while table refs are scalar ids.
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Query-built multis are runtime-typed and safe. Worked around here
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(single ref local, bucket-major seeding); the compiler fix is its own
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slice.
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## Reference-machine numbers (first campaign, 2026-08-21)
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`bench/baseline.json` is the contract; headline readings:
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- ram seed 245–290k inserts/s; **durable seed ≈4.5k/s** (fsync-per-commit
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≈220µs each — the gap iteration 23 exists to close).
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- reads/queries ≈1.1–1.3M ops/s at p50 1µs since the read-path index
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slice (2026-08-22, engine `wo_idx_probe` + emitter index selection) —
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up from ≈1.5k/s at p50 600µs when point lookups walked every slab
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(~×850). mixread 89k ops/s single-shard, ~1.9k multi-shard (was
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1,280 / 21): the RPC round-trip is now the visible cost, as designed.
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- msgrate ≈13M msgs/s same-heap vs ≈2.4M cross-shard (the mutex-inbox
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number, stage-2 deviation 4).
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- Tolerance policy lives in the DRIVER (`tolerance_for`), not hand-edits
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— a baseline refresh regenerates it: mix*/sN/read/query 50%
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(scheduling + µs-scale jitter), rest 15%; latency floors
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`max(4×value, 100µs)` — the tripwire means "µs became ms".
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## The gate must bite (proven 2026-08-21)
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`scripts/db-bench.py --check <results.json>` evaluates a recorded run:
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the real results pass 74/0; a doctored copy FAILS on exactly the
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doctored metrics — use a 15%-class metric (seed) halved plus a
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50%-class metric (read) quartered, so both tolerance classes prove they
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bite. Re-run the smoke after any gate or policy change.
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