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feat(raft-ha-core-safety): establish snapshot (term,lsn) boundary on install (task 3.2)

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Adds checkpointTerm (@6, append-only) to the SnapshotTransfer wire
message. The leader stamps it via persist_entry_term(p, checkpoint_lsn)
when sending a snapshot; the standby reconciles it into its own
per-LSN term index (persist_reconcile_checkpoint_term) right after
persist_load_snapshot succeeds, before applied_lsn advances. This
authoritatively overwrites any stale local term a divergent
pre-snapshot entry left at the checkpoint LSN, closing the gap task
3.1's RED test proved (Expected 7 Was 3 -> now passes). Transport
stays persist_t-free; the reconcile lives in persist.c per the
existing dependency direction. Decode is auto-generated via capnp
mapname; only the hand-rolled encode path (request.c/typemap.h, needed
for the raw snapshot payload) required a matching manual update.

test_ha_core_safety 25/0, test_config_repl 66/0, no ASAN reports.
This commit is contained in:
Rongsong Shen 2026-07-01 13:08:10 +00:00
parent 21858faba4
commit a53b9a7b6c
11 changed files with 132 additions and 23 deletions
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23
src/controller/persist.c
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@ -505,6 +505,29 @@ uint64_t persist_entry_term(const persist_t* p, uint64_t lsn)
return result;
}
/* persist_reconcile_checkpoint_term — raft-ha-core-safety task 3.2 (Req
* 3.1/5.1), Snapshot Boundary Reconcile. See persist.h for the full contract.
* Reuses record_entry_term (same translation unit) to authoritatively
* overwrite whatever term (if any) the local term index held at
* checkpoint_lsn — this is a genuine reconcile-overwrite, not an idempotent
* skip, because a pre-snapshot divergent entry may have left a stale local
* term at this exact LSN. Only the checkpoint LSN's own term is reconciled:
* post-install Raft semantics mean no AppendEntries prevLogIndex/prevLogTerm
* check against this member ever references an LSN below the checkpoint
* again (the checkpoint is the new log-start boundary), and the WAL bytes
* below it were compacted away, so there is no data to reconstruct a full
* per-LSN history from even if it were needed. */
void persist_reconcile_checkpoint_term(persist_t* p, uint64_t checkpoint_lsn,
uint64_t checkpoint_term)
{
if (!p || checkpoint_lsn == 0)
return;
pthread_mutex_lock(&p->lock);
record_entry_term(p, checkpoint_lsn, checkpoint_term);
pthread_mutex_unlock(&p->lock);
}
/* ------------------------------------------------------------------ */
/* Public API */
/* ------------------------------------------------------------------ */