Black-box SIGKILL fuzzer for the M0 mmap+WAL crash story. Random write
workload through the official driver, kill -9 at a random point, reopen the
same log, verify the recovered state against an in-memory model:
- prefix invariant: recovered state == history[0..m) for some m in
[acked, sent]; every acked write durable, in-flight commands all-or-nothing
(group commit), nothing after them may survive
- always-opens (replay never refuses); index presence tied to the prefix and
find({k:v}) correctness (rebuild after replay); countDocuments
- unexpected server death (Zig panic, replay refusal) is a finding with the
server log; --verify-exec read-backs updates to separate execution bugs
from replay bugs; --no-kill for graceful-restart runs; --heavy passes a
1 MiB compact threshold to fuzz compaction/checkpoint windows
Deterministic via seeded PRNG; failures dump a repro artifact with the seed.
Mutation-checked: over-strict prefix check goes red on lost in-flight ops.
Observation recorded: small churn-heavy DBs can exhaust the pager's 64 GB
address-space reservation (data file grows in >=8 MiB compounding steps and
never shrinks without a rebuild), surfacing as DatabaseTooLarge on writes.
Aleksey Shakhmatov
6c7f1f2e77