On the standby replicated-apply path, ha_apply_single_entry wrote the entry via
persist_wal_write_replicated (which correctly set the self-computed CRC chain
link p->last_crc), then called apply_wal_entry with a SYNTHETIC header whose
crc=0. apply_wal_entry's `p->last_crc = hdr->crc` clobbered the chain link with
0, so every subsequent replicated write stamped prev_crc=0 on disk. The on-disk
CRC chain broke at the second replicated entry — invisible while live (standbys
serve in-memory state) but fatal on COLD RESTART: replay hit the break, returned
RECOVER_TRUNCATED, recovered only the config prefix, and lost all committed jobs
(joblist=0). The sticky truncated verdict then drove a promotion-fence
availability wedge (bug-777) when every survivor was truncated.
Fix — single ownership of the WAL header + CRC chain:
- apply_wal_entry is now LOGICAL entity-restore only: signature
(p, type, lsn, payload, payload_len); no header. It advances the current_lsn
high-water (monotonic) but NEVER touches p->last_crc.
- The physical layer is the sole owner of the CRC chain: persist_wal_write_-
replicated on the live path, replay_wal/persist_recover on recovery.
- ha_apply_single_entry drops the fabricated header and passes entry fields
directly. The persist_recover replay caller is updated to the new signature.
Verified: new RED->GREEN test test_replicated_apply_chain_survives_cold_restart
(drives the real ha_apply_wal_catchup_entry path, cold-replays -> RECOVER_CLEAN,
all N recovered); controller suite 0 failures; 3-node rolling-SIGKILL soak on a
real ext2/3 fs now passes 5/5 (was wedge+loss at round 3); full cold restart
recovers all 6 committed jobs (was 0) with CLEAN verdicts and a normal election.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Rongsong Shen
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