chore(scheduler-allocator-runner): implementation complete; log bug-1897

Feature validation GO (ASAN scheduler suite 96/96, smoke replay clean on
the allocation path). Roadmap entry marked implemented with follow-ups.

bug-1897 (found by the validation smoke run, not caused by this feature):
xce_scheduler --sim segfaults in limit_job_election on a job whose
snapshot resreq failed to parse (pre-bug-1888-fix replays).

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

2026-09-30 10:20:39 +00:00

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bug-1897: xce_scheduler --sim segfaults in limit_job_election on a job whose snapshot resreq failed to parse

Description

Observed: replaying data/scheduler-replay-20260928-064842.replay in simulation mode crashes before any decision, 3/3 runs:

[ERROR] [xce_sched_core_load_snapshot] xce_sched_core_load_snapshot parse_resreq failed for jobid 4667606771186008064: Primary: ...
==2723571==ERROR: AddressSanitizer: SEGV on unknown address 0x000000000008 (pc 0x555555a7cb6e ... T3)
    #0 limit_job_election ../scheduler/src/plugins/limit.c:336
    #1 plugin_job_election ../scheduler/src/plugin.c:601
    #2 sched_allocator ../scheduler/src/sched_election.c:236

The replay's snapshot stores resreqs in the debug-dump format that bug-1888 wrote before its fix. Since the bug-1887 fix, parse_resreq rejects that text, so the snapshot loader logs the error but keeps the job with no schedobj. The allocator thread's job election then reads job->schedobj as NULL in the limit plugin.

Expected: a job whose resreq cannot be parsed from a snapshot is either dropped (with the error logged) or kept pending with a reason, and never reaches election with a NULL schedobj; the simulator must not crash on an old replay.

Impact: crash (SIGSEGV) of xce_scheduler --sim on any replay whose snapshot has unparsable resreqs, including every replay captured before the bug-1888 fix. Suspected: the same path could crash a normal-mode scheduler loading such a snapshot (not tried).

Found by: feature-level validation smoke run of spec scheduler-allocator-runner (2026-09-30); not caused by that feature (limit.c, snapshot_load.c, sched_election.c untouched by it).

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 (src/build.alloc, dedicated scheduler-allocator-runner build dir); ASAN_OPTIONS=detect_leaks=0
Code: scheduler-framework @ 28cff179-dirty
Deployment: none (simulation mode, xce_scheduler --sim, no controller or workers)

Reproduction

git checkout 28cff179 (or later); bash src/tools/xce-build.sh scheduler asan build.alloc --jobs 8
cd src && nix develop . --command bash -c 'ASAN_OPTIONS=detect_leaks=0 ./build.alloc/scheduler/xce_scheduler --sim=/home/claude/tmp/bug-1897/scheduler-replay-20260928-064842.replay -l /tmp/sim.log'
Observe parse_resreq failed errors in the log, then the ASan SEGV in limit_job_election.

Frequency: deterministic (3/3 runs, 2026-09-30)
Evidence: /home/claude/tmp/bug-1897/ (replay file copy, run.out with the ASan report, sim.log)

Root cause

TODO: required for fixed/partial

Fix