fix: Drop incorrect max_slots support code [FOUNDENG-454] (#691)

The expconf resources.max_slots attribute is documented as managed by
Slurm, but there was a partial (non-functional) implementation in
DispatchRM as well.  If we ever submitted max_slots worth of work
the remainder would remain QUEUED forever.   I did attempt to fix
the existing support, but the obvious fixes were not sufficient.  Since
this is already documented as managed by Slurm, just remove the support
and let the workload managers manage it.

master/internal/rm/dispatcherrm/dispatcher_resource_manager.go

@@ -261,7 +261,6 @@ type dispatcherResourceManager struct {
 	reqList                       *tasklist.TaskList
 	groups                        map[*actor.Ref]*tasklist.Group
 	dispatchIDToAllocationID      map[string]model.AllocationID
-	slotsUsedPerGroup             map[*tasklist.Group]int
 	masterTLSConfig               model.TLSClientConfig
 	loggingConfig                 model.LoggingConfig
 	jobWatcher                    *launcherMonitor
@@ -316,7 +315,6 @@ func newDispatcherResourceManager(
 		reqList:                  tasklist.New(),
 		groups:                   make(map[*actor.Ref]*tasklist.Group),
 		dispatchIDToAllocationID: make(map[string]model.AllocationID),
-		slotsUsedPerGroup:        make(map[*tasklist.Group]int),
 
 		masterTLSConfig:      masterTLSConfig,
 		loggingConfig:        loggingConfig,
@@ -849,7 +847,6 @@ func (m *dispatcherResourceManager) receiveRequestMsg(ctx *actor.Context) error
 		m.getOrCreateGroup(ctx, msg.Handler).MaxSlots = msg.MaxSlots
 
 	case tasklist.GroupActorStopped:
-		delete(m.slotsUsedPerGroup, m.groups[msg.Ref])
 		delete(m.groups, msg.Ref)
 
 	case sproto.SetAllocationName:
@@ -1729,8 +1726,6 @@ func (m *dispatcherResourceManager) assignResources(
 		}
 	}
 
-	m.slotsUsedPerGroup[m.groups[req.Group]] += req.SlotsNeeded
-
 	if len(rID) == 0 {
 		rID = sproto.ResourcesID(uuid.NewString())
 	}
@@ -1781,12 +1776,6 @@ func (m *dispatcherResourceManager) assignResources(
 func (m *dispatcherResourceManager) resourcesReleased(ctx *actor.Context, handler *actor.Ref) {
 	ctx.Log().Infof("resources are released for %s", handler.Address())
 	m.reqList.RemoveTaskByHandler(handler)
-
-	if req, ok := m.reqList.TaskByHandler(handler); ok {
-		if group := m.groups[handler]; group != nil {
-			m.slotsUsedPerGroup[group] -= req.SlotsNeeded
-		}
-	}
 }
 
 // Used on DEBUG startup, to queue a terminate and delete all dispatches in the DB
@@ -1834,7 +1823,6 @@ func (m *dispatcherResourceManager) getOrCreateGroup(
 	priority := config.KubernetesDefaultPriority
 	g := &tasklist.Group{Handler: handler, Weight: 1, Priority: &priority}
 	m.groups[handler] = g
-	m.slotsUsedPerGroup[g] = 0
 
 	if ctx != nil && handler != nil { // ctx is nil only for testing purposes.
 		actors.NotifyOnStop(ctx, handler, tasklist.GroupActorStopped{})
@@ -1845,14 +1833,8 @@ func (m *dispatcherResourceManager) getOrCreateGroup(
 func (m *dispatcherResourceManager) schedulePendingTasks(ctx *actor.Context) {
 	for it := m.reqList.Iterator(); it.Next(); {
 		req := it.Value()
-		group := m.groups[req.Group]
 		assigned := m.reqList.Allocation(req.AllocationRef)
 		if !tasklist.AssignmentIsScheduled(assigned) {
-			if maxSlots := group.MaxSlots; maxSlots != nil {
-				if m.slotsUsedPerGroup[group]+req.SlotsNeeded > *maxSlots {
-					continue
-				}
-			}
 			m.assignResources(ctx, req)
 		}
 	}

master/internal/rm/dispatcherrm/dispatcher_resource_manager_test.go

@@ -464,7 +464,6 @@ func Test_dispatcherResourceManager_selectDefaultPools(t *testing.T) {
 		hpcResourcesManifest     *launcher.Manifest
 		reqList                  *tasklist.TaskList
 		groups                   map[*actor.Ref]*tasklist.Group
-		slotsUsedPerGroup        map[*tasklist.Group]int
 		dispatchIDToAllocationID map[string]model.AllocationID
 		masterTLSConfig          model.TLSClientConfig
 		loggingConfig            model.LoggingConfig
@@ -574,7 +573,6 @@ func Test_dispatcherResourceManager_selectDefaultPools(t *testing.T) {
 				hpcResourcesManifest:     tt.fields.hpcResourcesManifest,
 				reqList:                  tt.fields.reqList,
 				groups:                   tt.fields.groups,
-				slotsUsedPerGroup:        tt.fields.slotsUsedPerGroup,
 				dispatchIDToAllocationID: tt.fields.dispatchIDToAllocationID,
 				masterTLSConfig:          tt.fields.masterTLSConfig,
 				loggingConfig:            tt.fields.loggingConfig,