fix(scheduler): check slots/rusage for primaries nested in COMPOUND/ALTER (bug-1768)

seqjob_prepare_allocation() and parjob_prepare_allocation() returned 0
whenever ctx->schedobj was not PRIMARY, so a primary nested in a COMPOUND
(or ALTER) job never had its slot count or rusage checked: a 5-task
compound dispatched onto 4 slots, and an ALTER job was "placed" by its
first alternative with an empty (0-slot) allocation. Both hooks now
compute the want from ctx->primary -- the primary being allocated, set by
sched_ctx_set_primary() for nested primaries and identical to
obj->u.primary->resreq for PRIMARY jobs.

sched_ctx_set_primary() also clears ctx->worker, so the next primary of a
compound computes its job-level want rather than a per-host want left
over from the previous primary's host (PRIMARY jobs set it once, with
worker already NULL).

Tests (real ingest + live allocator): a 5-task COMPOUND on 2x2 slots now
PENDs; "{5*{..}} || {1*{..}}" falls back to the second alternative (1
slot). Both failed before. Scheduler suite 87/87.

Follow-up logged: bug-1863 (multi-primary COMPOUND keeps only the last
primary's allocation).

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

src/scheduler/src/plugins/parjob_allocator.c

@@ -98,12 +98,11 @@ static int parjob_prepare_allocation(void* arg, xce_sched_ctx_t* ctx)
         return -EINVAL;
     }
 
-    if (obj->tag != XCE_RESREQ_PRIMARY) {
+    /* bug-1768: the primary being allocated is ctx->primary -- for a
-        /* we just take care of parallel job */
+     * PRIMARY obj it is obj->u.primary->resreq, and for a COMPOUND/ALTER
-        return 0;
+     * obj it is the nested primary sched_ctx_set_primary() just set. Gating
-    }
+     * on obj->tag skipped every nested primary's slots/rusage check. */
-
+    primary = ctx->primary;
-    primary = obj->u.primary->resreq;
     if (primary == NULL) {
         return -EINVAL;
     }

src/scheduler/src/plugins/seqjob_allocator.c

@@ -61,12 +61,11 @@ static int seqjob_prepare_allocation(void* arg, xce_sched_ctx_t* ctx)
         return -EINVAL;
     }
 
-    if (obj->tag != XCE_RESREQ_PRIMARY) {
+    /* bug-1768: the primary being allocated is ctx->primary -- for a
-        /* we just take care of sequence job */
+     * PRIMARY obj it is obj->u.primary->resreq, and for a COMPOUND/ALTER
-        return 0;
+     * obj it is the nested primary sched_ctx_set_primary() just set. Gating
-    }
+     * on obj->tag skipped every nested primary's slots/rusage check. */
-
+    primary = ctx->primary;
-    primary = obj->u.primary->resreq;
     if (primary == NULL) {
         return -EINVAL;
     }

src/scheduler/src/schedobj.c

@@ -531,6 +531,11 @@ void sched_ctx_fini(xce_sched_ctx_t* ctx)
 void sched_ctx_set_primary(xce_sched_ctx_t* ctx, xce_primary_resreq_t* primary)
 {
     ctx->primary = primary;
+    /* bug-1768: a COMPOUND sets one primary after another on the same ctx;
+     * a host left over from the previous primary would make the prepare
+     * below compute a per-host want instead of this primary's job-level
+     * (shared) want */
+    ctx->worker = NULL;
 
     /* scheduler-sim-live-allocation spec, task 2.1 (Core-Safe Allocation
      * Chain): ctx->sched is now honestly typed xce_sched_core_t* (set by

src/scheduler/testsuite/test_parjob_e2e_multislot.c

@@ -701,6 +701,102 @@ static void test_alter_resreq_job_dispatches_via_real_allocator(void)
     TEST_ASSERT_EQUAL_UINT64(jobid, decision->u.alloc->jobid);