---
id: "bug-1768"
status: "fixed"
status_updated: "2026-09-25"
status_note: "b4e9a099"
component: "scheduler"
severity: "crash"
timestamp: "2026-09-04T00:00:00Z"
last_seen: "2026-09-19T09:00:00Z"
occurrences: 1
files: []
tags: ["scheduler", "resource-accounting", "compound-resreq", "alter-resreq", "pre-existing", "severity-high", "scheduler-allocation-discovery"]
related: ["bug-1767"]
fix_commits: ["b4e9a099"]
legacy: true
---

# bug-1768: out-of-scope gap discovered during scheduler-allocation task 5.1's review (cache/dispatch wiring)

## Description
OPEN, NOT A CRASH -- pre-existing, out-of-scope gap discovered during scheduler-allocation task 5.1's review (cache/dispatch wiring). seqjob_prepare_allocation() (src/scheduler/src/plugins/seqjob_allocator.c) and parjob_prepare_allocation() (src/scheduler/src/plugins/parjob_allocator.c) both silently `return 0` whenever `ctx->schedobj->tag != XCE_RESREQ_PRIMARY`. For a primary resource request nested inside a COMPOUND (or, transitively, an ALTER) job, `ctx->schedobj` remains the enclosing COMPOUND object for the entire per-primary allocation loop -- it is never swapped to a per-primary object -- so this guard fires for every nested primary and both prepare-allocation hooks no-op unconditionally.

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

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

## Root cause
CONFIRMED via direct code read and `git log --follow -p`: the `ctx->schedobj->tag != XCE_RESREQ_PRIMARY` guard predates the entire scheduler-allocation feature (introduced in commit 12dcc2a6, months before this branch's base commit 5a670676); task 3.1's seqjob rewrap (b18c5f78) did not touch or introduce it. Effect: `ctx->alloc_req.host`/`ctx->alloc_req.shared` are never populated for a nested primary's resource want, so `sched_check_host_satisfy()` trivially passes against an empty want vector regardless of a candidate host's real free capacity. Only the SELECT expression (if the resreq specifies one) still gates candidate hosts for a nested primary -- slot count and rusage (memory, etc.) are unconditionally treated as satisfied. This means every COMPOUND job (and transitively every ALTER job, since ALTER delegates to COMPOUND dispatch) with a nested primary resource request has never had its real slots/rusage availability checked by the scheduler, since this guard was introduced.

## Fix
NOT FIXED -- discovered and characterized during scheduler-allocation task 5.1's independent review (2026-09-04); deliberately left out of that task's scheduler.c-dispatch boundary. Fixing requires either (a) constructing/staging a transient per-primary schedobj view when dispatching a nested primary through prepare_allocation (mirroring task 5.1's own sched_primary_cache_obj_() stack-local-schedobj pattern used for cache-key synthesis), or (b) relaxing seqjob_prepare_allocation()/parjob_prepare_allocation()'s guard to operate directly on ctx->primary (already available on ctx regardless of the enclosing schedobj's tag) instead of gating on ctx->schedobj->tag at all. Needs its own dedicated bugfix task/spec given the severity and blast radius (all COMPOUND/ALTER jobs, not scoped to scheduler-allocation).

UPDATE (2026-09-25): 2026-09-25 (bug-1769 fix 1ecd348f): with ALTER now allocating for real, this gap is what prevents a test where an ALTER alternative genuinely fails and the next one is used -- compound/alter-nested primaries never check slot/rusage availability, so every alternative 'fits'.

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

## References
- Related: bug-1767