---
id: "bug-845"
status: "fixed"
status_updated: "2026-09-24"
status_note: ""
component: "lib"
severity: "unknown"
timestamp: "2026-06-20T14:30:00.000Z"
last_seen: "2026-09-19T09:00:00Z"
occurrences: 2
files: ["src/lib/hook.c (xce_add_hook idempotency); root path src/controller/{persist.c persist_start", "ha.c ha_register_persist_hooks}"]
tags: ["double-register", "duplicate", "ha", "hook-dedup", "investigation", "job-submit", "persistence", "wal", "waldump"]
related: ["bug-795", "bug-828"]
legacy: true
---

# bug-845: Every committed job appears as TWO consecutive WAL_JOB_SUBMIT entries with the SAME jobid (e.g

## Description
Every committed job appears as TWO consecutive WAL_JOB_SUBMIT entries with the SAME jobid (e.g. ctrl-1 LSN 2,3 = jobid 1868520205844480). Surfaced by waldump on /tmp/xce-ha-deploy.

## Environment
_Not recorded (migrated from buglog.json)._

## Reproduction
_Not recorded (migrated from buglog.json)._

## Root cause
NOT array expansion — job_submit() assigns array members DISTINCT ids (base_id+i, job.c) and the Job capnp schema has a single jobid field, so identical-jobid pairs cannot be two array tasks. A single client submit is producing two WAL_JOB_SUBMIT appends of the same job. EXACTLY 2 entries per job (never 1 or 3), always at ADJACENT LSNs, for every job on every node. CONFIRMED via enhanced waldump (payload-CRC + subtime columns): each pair is BYTE-IDENTICAL (same PCRC, e.g. LSN 2,3 both 6d79074e; same subtime 1781959730) — proving a literal double-append of the SAME encoded job_t in one submit flow; a failover retry would re-stamp subtime=time(NULL) and differ, so retry is DEFINITIVELY ruled out. Remaining candidates: AFTER_EVENT jlist contains the job twice, or the JOB_NEW hook/handler persists twice per submit. So 'ctrl-1 has 12 submits' is really 6 jobs (halve when reconciling failover-test job totals). Doubles LSN consumption; consistent across nodes here (F@14,15 on both ctrl-1 and ctrl-3) so not itself divergence, but a latent cross-node LSN-divergence risk if the duplicate count ever varies by primary.

## Fix
FIXED 2026-06-23 (src/lib/hook.c). Root cause: persist_job_hook_fun was registered on XCE_CONTROLLER_HOOK_JOB by TWO owners — persist_start() (unconditional, boot) AND ha_register_persist_hooks() (on PRIMARY promotion) — with the SAME persist_t closure. xce_add_hook did not dedup, xce_run_hooks fires ALL slots, so a promoted primary had 2 active slots => persist_job_hook_fun ran twice per submit => 2 byte-identical adjacent WAL_JOB_SUBMIT appends. Fix: made xce_add_hook idempotent on exact (fn,data) — re-registering an active (fn,data) is a no-op; same fn with DISTINCT data still registers (legitimate multi-closure). Preserves the persist_start test contract many unit tests rely on. Verified: WAL now single-entry per job (waldump); 5/5 hook unit tests; controller suite 343 tests 0 new failures; 3/3 post-fix HA soaks zero job loss. NOTE: an earlier post-fix soak hit the KNOWN intermittent failover durability race (bug-795/828 class, LSN-10 cross-node divergence) — confirmed pre-existing (baseline passes/fails on timing too), NOT caused by this dedup.

## Verification
_Not recorded (migrated from buglog.json)._

## References
- Related: bug-795, bug-828