Non-dispatch gateways no longer open per-board kanban DBs for notifier
polling. Mirrors the existing dispatcher gate (config
kanban.dispatch_in_gateway, default True; env override
HERMES_KANBAN_DISPATCH_IN_GATEWAY) so multi-gateway setups collapse to a
single process holding kanban.db file descriptors.
Salvaged from PR #31964 by @steveonjava; tests and docs trimmed during
salvage.
apply_wal_with_fallback() issued PRAGMA journal_mode=WAL on every call,
including connections to DBs already in WAL mode. This triggered the WAL
init code path, causing SQLite to acquire EXCLUSIVE, checkpoint, and unlink
kanban.db-{wal,shm}. Other open connections received (deleted) FDs and
raised sqlite3.OperationalError: disk I/O error.
Add a cheap read probe (PRAGMA journal_mode, no flock/checkpoint/unlink)
before the set-pragma path. If already wal, return early. The set-pragma
and DELETE fallback paths are unchanged.
Closes#31158. Addresses root cause that PRs #32226 and #32322 attempted
via connection-sharing/caching approaches.
Reaper now runs at the top of every dispatcher tick regardless of per-board connect() failures. Previously the reaper sat inside dispatch_once after the kanban_db.connect() call — any EIO during connect would skip reaping for that tick, accumulating zombie workers and stale claim_lock rows.
Also: reap_worker_zombies now returns the list of reaped pids (the dispatcher logs them) and a test indentation fix.
Squashes three sibling commits from PR #32301 into one logical change for batch review.
`detect_crashed_workers` calls `_pid_alive` on every `running` task whose
claim is held by this host. The check can transiently return False for a
freshly-spawned worker (fork → /proc-visibility lag, or reap-race
between SIGCHLD and parent reaping). When a second dispatcher ticks
inside that window it reclaims the task and spawns a duplicate worker.
Add `DEFAULT_CRASH_GRACE_SECONDS = 30` and an
`HERMES_KANBAN_CRASH_GRACE_SECONDS` env-var override.
`detect_crashed_workers` skips the liveness check when
`time.time() - started_at < grace`. The existing 15-minute claim TTL
still reclaims genuinely-crashed workers; grace only suppresses the
launch-window false positive.
`HERMES_KANBAN_CRASH_GRACE_SECONDS=0` is set on the `kanban_home`
fixture in `test_kanban_core_functionality.py` so existing tests that
assert immediate reclaim retain pre-fix semantics.
Companion to merged PR #23442 (`release_stale_claims`, closes#23025),
which addressed the same multi-dispatcher race in the stale-claim path.
Related: #20015 (`_pid_alive` false-negative behaviour),
When code inside a write_txn block raises an OperationalError that SQLite
has already auto-rolled-back (typical for disk I/O error,
database is locked, and database disk image is malformed), the
explicit ROLLBACK in write_txn.__exit__ itself raises
cannot rollback - no transaction is active and the secondary exception
replaces the original in the traceback. Operators see a misleading error
and lose the diagnostic information they need.
Swallow the rollback-time OperationalError so the caller always sees the
original cause.
Confirmed reproducer: tests/hermes_cli/test_kanban_db.py::
test_write_txn_preserves_original_exception_when_rollback_fails
apply_wal_with_fallback() treated "disk i/o error" as a permanent
WAL-incompatibility marker, identical to "locking protocol" (NFS) and
"not authorized" (FUSE). But EIO during PRAGMA journal_mode=WAL is
typically TRANSIENT — page-cache pressure, brief lock contention,
recoverable storage hiccups — not a permanent filesystem property.
Treating transient EIO as a permanent downgrade signal produces the
mixed-journal-mode-across-processes corruption pattern:
1. Process A opens kanban.db, hits transient EIO on the WAL pragma,
silently downgrades to journal_mode=DELETE.
2. Process B (no EIO) opens the same file moments later and
successfully sets journal_mode=WAL.
3. A writes rollback-journal frames while B writes WAL frames. SQLite
documents this as unsupported and corrupts the file:
https://www.sqlite.org/wal.html ("all connections to the same
database must use the same locking protocol").
This was the root cause of repeated kanban.db corruption on hosts with
multiple gateway processes plus CLI invocations against the same DB
(observed pattern: corruption shortly after gateway startup, after the
process logged "WAL journal_mode unsupported on this filesystem (disk
I/O error) — falling back to journal_mode=DELETE"). The fallback
warning told the truth — fallback DID happen — but the premise
("unsupported on this filesystem") was wrong; the EIO was a one-shot
event and sibling processes successfully used WAL.
Fix has two layers:
1. Remove "disk i/o error" from _WAL_INCOMPAT_MARKERS. EIO now re-raises
so callers can retry instead of silently corrupting the DB. The two
remaining markers ("locking protocol", "not authorized") are
deterministic per filesystem so they remain safe permanent-downgrade
signals.
2. Belt-and-suspenders: before downgrading on ANY marker match, peek the
on-disk journal mode. If the header says WAL, refuse to downgrade and
re-raise the original error. This guards against any future addition
to _WAL_INCOMPAT_MARKERS turning out to be transient in some
environment we haven't yet seen.
Tests:
- tests/test_hermes_state_wal_fallback.py:
* Flipped test_falls_back_on_disk_io_error → test_reraises_on_disk_io_error
asserting EIO is re-raised, not silently swallowed.
* Added test_does_not_downgrade_when_disk_says_wal covering the
on-disk-header safety guard for the existing legitimate markers.
- tests/hermes_cli/test_kanban_db.py:
* test_connect_falls_back_to_delete_on_locking_protocol now uses a
truly-fresh DB (instead of the kanban_home fixture which pre-inits
in WAL). On NFS the very first process touching the file legitimately
downgrades; on a file already in WAL the new guard correctly refuses.
A standalone reproducer lives at /tmp/kanban-stress/repro_bugD_eio_wal_downgrade.py
(not committed): without fix the DB silently flips from WAL to DELETE
mid-process; with fix the EIO surfaces and the file stays WAL.
Refs: Bug D in the kanban-corruption investigation series (Bugs A and C
shipped in ebe7374f3 and e02147d5e respectively). Bug D explains every
corruption incident this week including those that survived A's
single-dispatcher mitigation, because every CLI invocation is a
separate process whose WAL pragma can transiently fail.
Production corruption #6 left b-tree pages with zeroed headers but intact old cell content — the Bug E pattern. This fix applies three pragma calls on every connect():
- synchronous=FULL (was NORMAL): closes the WAL-checkpoint reordering window where a crash between WAL commit and main-DB write leaves a partially-written b-tree page header. Cost is <1ms per commit on local SSD; negligible at kanban write volume.
- secure_delete=ON: forces SQLite to zero freed page bytes on disk. If a torn write or hardware fault later corrupts a page, the underlying cell content is zero, so corruption is detectable and no stale rows can resurface as live data.
- cell_size_check=ON: adds a read-side guard so corrupt cells surface as errors at read time rather than as silent wrong-data returns.
All three are connection-scoped and re-applied on every connect(). secure_delete also writes a persistent flag into the DB header on the first call against a fresh DB, making the protection durable across processes for new DBs.
Tests added for all four required cases: each pragma active on a fresh connection, and all three re-applied after close+reopen. Also adds the required negative test (migration path does not reset pragmas).
Stephen Chin