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feat(raft-apply-decoupling): resolve pending continuations on demotion/truncation (task 1.4)

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commit_resolve_pending_above(ce, lsn_floor, rc) fails every registered
continuation for lsn > lsn_floor, reusing commit_resolve()'s existing
exactly-once/idempotent guarantee (no parallel bookkeeping path).

Truncation: a new on_truncate/truncate_cb_ctx callback on persist_t
(same inversion-of-control shape as the existing on_durable_advance
hook) fires from persist_truncate_wal_above after releasing p->lock,
only when entries were actually removed. This one wrapper covers all
three real truncation call sites: raft_cb_become_leader's
post-election truncate, the library's on_truncate_from
conflict-reconcile, and ha_demotion_convergence_fn's post-demotion
truncate.

Demotion: raft_cb_become_follower calls
commit_resolve_pending_above(&c->commit, 0, -XCE_ERR_STANDBY) --
lsn_floor=0 fails everything, since a demoted node can never
authoritatively confirm anything still pending (CP posture).

Without this, a demoted or truncated node would leave any pending
async command permanently unresolved -- the requester would simply
never get a reply, worse than today's bounded-timeout behavior.

Also closes bug-1407 (pre-existing test_config_repl flake, unrelated
to this feature) -- confirmed fixed as a side effect of prior tasks
in this series, 70/70 passing across 3 independent runs.
This commit is contained in:
Rongsong Shen 2026-07-03 11:58:10 +00:00
parent 530a02bda3
commit 9b4b805a27
9 changed files with 748 additions and 301 deletions
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26
src/include/persist.h
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@ -340,6 +340,22 @@ struct persist_s {
void (*on_durable_advance)(void* ctx);
void* durable_cb_ctx;
/* Truncation wake hook (raft-apply-decoupling task 1.4). Persistence owns
* this slot; the commit engine REGISTERS a callback (ctx = the
* commit_engine_t) via persist_set_truncate_cb, mirroring
* on_durable_advance's registration pattern and dependency direction
* (persist only stores+calls an opaque function pointer; it never
* depends on commit.c). persist_truncate_wal_above invokes it AFTER it
* actually removes entries above the new tail and AFTER releasing
* p->lock, so any commit continuation registered for an LSN above the
* new tail (which can never commit -- its entry no longer exists) is
* resolved FAILED promptly instead of waiting out the commit engine's
* timeout sweep. NOT invoked on a no-op truncate (nothing above
* cutoff_lsn -- current_lsn unchanged). NULL until registered (a
* truncate is then a silent no-op wake). */
void (*on_truncate)(void* ctx, uint64_t cutoff_lsn);
void* truncate_cb_ctx;
/* Checkpoint (stubs for now — wired in Task 10) */
atomic_int checkpoint_requested;
pthread_cond_t checkpoint_done;
@ -590,6 +606,16 @@ void persist_clear_recovery_unrecoverable(persist_t* p);
* unregister. Safe to call before persist_start (no flusher running yet). */
void persist_set_durable_cb(persist_t* p, void (*fn)(void* ctx), void* ctx);
/* Register a truncation wake callback (raft-apply-decoupling task 1.4).
* persist_truncate_wal_above calls fn(ctx, cutoff_lsn) after it actually
* truncates entries above cutoff_lsn (the new log tail) and after releasing
* p->lock -- fn MUST NOT take p->lock (same rule as persist_set_durable_cb;
* the commit engine's callback takes only ce->lock, keeping the lock order
* p->lock → ce->lock cycle-free). Not called for a no-op truncate (nothing
* above cutoff_lsn). Pass fn = NULL to unregister. */
void persist_set_truncate_cb(persist_t* p, void (*fn)(void* ctx, uint64_t cutoff_lsn),
void* ctx);
#ifdef XCE_TESTING
/* ============================================================
* Durability-verification test seam (ha-commit-durability Req 3.2, 3.3)