myxce/.wolf/bugs/bug-1874.md

id	status	status_updated	status_note	component	severity	timestamp	last_seen	occurrences	files	tags	related	fix_commits	gitea_issue	gitea_synced_status	gitea_synced_hash
bug-1874	fixed	2026-09-28		scheduler	noise	2026-09-28T03:52:37Z	2026-09-28T03:58:49Z	1	src/scheduler/src/plugin.c src/scheduler/src/schedobj.c	scheduler plugin picker logging		44173f74	312	fixed	525a89cedf6d

bug-1874: scheduler warns about deprecated job_elect_fn for xce_sched_fcfs on every start

Description

Observed:

[2026-09-28 11:52:49,740] [51152] [  WARN] [       plugin_register] plugin 'xce_sched_fcfs' selects jobs via the deprecated job_elect_fn hook; migrate to xce_job_picker_iface_t (scheduler-core spec, Req 5 'Migration from old job_elect_fn')

Expected: no warning: the normal-mode job picker is builtin_fcfs, not the legacy plugin. Impact: a WARN on every scheduler start that asks the operator to migrate something they do not use; noise only. Found by: user report from a pc13v HA deploy, 2026-09-28

Environment

• OS: no /etc/os-release; Docker container; NixOS kernel; kernel Linux 6.18.33 x86_64
• libc: glibc 2.42-47 (interpreter /nix/store/wb6rhpznjfczwlwx23zmdrrw74bayxw4-glibc-2.42-47/lib/ld-linux-x86-64.so.2)
• Toolchain: gcc (GCC) 15.2.0, meson 1.9.1
• Build: asan (xce.build)
• Code: scheduler-framework @ 8cadeeb2 (last commit without the fix)
• Deployment: first seen on pc13v: 3-node HA (ctrl-1..3) + scheduler + apiserver + real root xcecd under systemd, deploy dir /tmp/xce-ha-deploy, 2026-09-28 11:52 +0800 (pc13v's OS, libc and exact commit were not recorded; the values above are from the reproduction on this dev host, same nix toolchain)

Reproduction

1. Start xce_scheduler at 8cadeeb2 (any deployment, e.g. /xce-deploy-ha)
2. grep 'deprecated job_elect_fn' <scheduler log>

• Frequency: deterministic (every start)
• Evidence: the xcecd/scheduler/controller/apiserver logs pasted in the user's report, 2026-09-28 (quoted above)

Root cause

sched_register_plugins() (scheduler.c) registers the legacy xce_sched_fcfs plugin on every start alongside builtin_fcfs, and plugin_register() (plugin.c) warned for every job_elect_fn-only plugin it adapted to the picker interface, whether or not that plugin would ever be selected. In normal mode the picker is always builtin_fcfs (sched_set_default_job_pick_plugin()); only --sim can name another.

Fix

plugin_register() still adapts a job_elect_fn plugin but only marks it (plugin->legacy_picker); sched_resolve_job_picker() (schedobj.c) logs the deprecation once (legacy_picker_warned) when such a plugin is actually selected as the picker.

Verification

• Test: test_legacy_picker_deprecation_flagged_on_selection_not_registration in src/scheduler/testsuite/test_picker_wiring.c (new: registration leaves legacy_picker_warned unset, selection sets it) and test_register_legacy_job_elect_fn_only_plugin_uses_wrapper_without_warning in test_plugin_picker_registration.c, which captures the log: 0 warnings at registration (it asserted 1 before the change)
• Suites: full ASAN build (xce-build all): 113/113 suites after the updated scheduler picker-registration test; controller 1250/0, harness 141/0, worker diskstats 4/0, scheduler picker wiring 11/0 + picker registration 4/0, apiserver TestRootWarning PASS
• Live: pc13v retest at 4c134127 (debug build, 2026-09-28 14:47 +0800): ag -i error logs/ finds nothing; ag -i warn logs/ shows only the WAL-unencrypted advisory; no job_elect_fn deprecation warning

References

• Related: none