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queue_scheduler.go
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queue_scheduler.go
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package scheduler
import (
"container/heap"
"context"
"math"
"reflect"
"time"
"github.com/grpc-ecosystem/go-grpc-middleware/logging/logrus/ctxlogrus"
"github.com/pkg/errors"
"github.com/sirupsen/logrus"
"github.com/armadaproject/armada/internal/common/logging"
schedulerconstraints "github.com/armadaproject/armada/internal/scheduler/constraints"
schedulercontext "github.com/armadaproject/armada/internal/scheduler/context"
"github.com/armadaproject/armada/internal/scheduler/interfaces"
"github.com/armadaproject/armada/internal/scheduler/nodedb"
)
// QueueScheduler is responsible for choosing the order in which to attempt scheduling queued gangs.
// Relies on GangScheduler for scheduling once a gang is chosen.
type QueueScheduler struct {
schedulingContext *schedulercontext.SchedulingContext
candidateGangIterator *CandidateGangIterator
gangScheduler *GangScheduler
}
func NewQueueScheduler(
sctx *schedulercontext.SchedulingContext,
constraints schedulerconstraints.SchedulingConstraints,
nodeDb *nodedb.NodeDb,
jobIteratorByQueue map[string]JobIterator,
) (*QueueScheduler, error) {
for queue := range jobIteratorByQueue {
if _, ok := sctx.QueueSchedulingContexts[queue]; !ok {
return nil, errors.Errorf("no scheduling context for queue %s", queue)
}
}
gangScheduler, err := NewGangScheduler(sctx, constraints, nodeDb)
if err != nil {
return nil, err
}
gangIteratorsByQueue := make(map[string]*QueuedGangIterator)
for queue, it := range jobIteratorByQueue {
gangIteratorsByQueue[queue] = NewQueuedGangIterator(sctx, it, constraints.MaxQueueLookback)
}
candidateGangIterator, err := NewCandidateGangIterator(sctx, gangIteratorsByQueue)
if err != nil {
return nil, err
}
return &QueueScheduler{
schedulingContext: sctx,
candidateGangIterator: candidateGangIterator,
gangScheduler: gangScheduler,
}, nil
}
func (sch *QueueScheduler) SkipUnsuccessfulSchedulingKeyCheck() {
sch.gangScheduler.SkipUnsuccessfulSchedulingKeyCheck()
}
func (sch *QueueScheduler) Schedule(ctx context.Context) (*SchedulerResult, error) {
log := ctxlogrus.Extract(ctx)
if ResourceListAsWeightedApproximateFloat64(sch.schedulingContext.ResourceScarcity, sch.schedulingContext.TotalResources) == 0 {
// This refers to resources available across all clusters, i.e.,
// it may include resources not currently considered for scheduling.
log.Infof(
"no resources with non-zero weight available for scheduling on any cluster: resource scarcity %v, total resources %v",
sch.schedulingContext.ResourceScarcity, sch.schedulingContext.TotalResources,
)
return &SchedulerResult{}, nil
}
if ResourceListAsWeightedApproximateFloat64(sch.schedulingContext.ResourceScarcity, sch.gangScheduler.nodeDb.TotalResources()) == 0 {
// This refers to the resources currently considered for schedling.
log.Infof(
"no resources with non-zero weight available for scheduling in NodeDb: resource scarcity %v, total resources %v",
sch.schedulingContext.ResourceScarcity, sch.gangScheduler.nodeDb.TotalResources(),
)
return &SchedulerResult{}, nil
}
nodeIdByJobId := make(map[string]string)
scheduledJobs := make([]interfaces.LegacySchedulerJob, 0)
for {
gctx, err := sch.candidateGangIterator.Next()
if err != nil {
sch.schedulingContext.TerminationReason = err.Error()
return nil, err
}
if gctx == nil {
break
}
if len(gctx.JobSchedulingContexts) == 0 {
continue
}
select {
case <-ctx.Done():
// TODO: Better to push ctx into next and have that control it.
err := ctx.Err()
sch.schedulingContext.TerminationReason = err.Error()
return nil, err
default:
}
if ok, unschedulableReason, err := sch.gangScheduler.Schedule(ctx, gctx); err != nil {
return nil, err
} else if ok {
for _, jctx := range gctx.JobSchedulingContexts {
scheduledJobs = append(scheduledJobs, jctx.Job)
if jctx.PodSchedulingContext != nil && jctx.PodSchedulingContext.Node != nil {
nodeIdByJobId[jctx.JobId] = jctx.PodSchedulingContext.Node.Id
}
}
} else if schedulerconstraints.IsTerminalUnschedulableReason(unschedulableReason) {
// If unschedulableReason indicates no more new jobs can be scheduled,
// instruct the underlying iterator to only yield evicted jobs from now on.
sch.candidateGangIterator.OnlyYieldEvicted()
}
}
if sch.schedulingContext.TerminationReason == "" {
sch.schedulingContext.TerminationReason = "no remaining candidate jobs"
}
if len(scheduledJobs) != len(nodeIdByJobId) {
return nil, errors.Errorf("only %d out of %d jobs mapped to a node", len(nodeIdByJobId), len(scheduledJobs))
}
return &SchedulerResult{
PreemptedJobs: nil,
ScheduledJobs: scheduledJobs,
NodeIdByJobId: nodeIdByJobId,
}, nil
}
// QueuedGangIterator is an iterator over queued gangs.
// Each gang is yielded once its final member is received from the underlying iterator.
// Jobs without gangIdAnnotation are considered gangs of cardinality 1.
type QueuedGangIterator struct {
schedulingContext *schedulercontext.SchedulingContext
queuedJobsIterator JobIterator
// Groups jobs by the gang they belong to.
jobsByGangId map[string][]interfaces.LegacySchedulerJob
// Maximum number of jobs to look at before giving up.
maxLookback uint
// Number of jobs we have seen so far.
jobsSeen uint
next *schedulercontext.GangSchedulingContext
}
func NewQueuedGangIterator(sctx *schedulercontext.SchedulingContext, it JobIterator, maxLookback uint) *QueuedGangIterator {
return &QueuedGangIterator{
schedulingContext: sctx,
queuedJobsIterator: it,
maxLookback: maxLookback,
jobsByGangId: make(map[string][]interfaces.LegacySchedulerJob),
}
}
func (it *QueuedGangIterator) Next() (*schedulercontext.GangSchedulingContext, error) {
if v, err := it.Peek(); err != nil {
return nil, err
} else {
if err := it.Clear(); err != nil {
return nil, err
}
return v, nil
}
}
func (it *QueuedGangIterator) Clear() error {
it.next = nil
return nil
}
func (it *QueuedGangIterator) Peek() (*schedulercontext.GangSchedulingContext, error) {
if it.hitLookbackLimit() {
return nil, nil
}
if it.next != nil {
return it.next, nil
}
// Get one job at a time from the underlying iterator until we either
// 1. get a job that isn't part of a gang, in which case we yield it immediately, or
// 2. get the final job in a gang, in which case we yield the entire gang.
for {
job, err := it.queuedJobsIterator.Next()
if err != nil {
return nil, err
}
if job == nil {
return nil, nil
}
if reflect.ValueOf(job).IsNil() {
return nil, nil
}
if !isEvictedJob(job) {
// Rescheduled jobs don't count towards the limit.
it.jobsSeen++
}
if it.hitLookbackLimit() {
return nil, nil
}
// Skip this job if it's known to be unschedulable.
if len(it.schedulingContext.UnfeasibleSchedulingKeys) > 0 {
if schedulingKey, ok := schedulingKeyFromLegacySchedulerJob(job, it.schedulingContext.PriorityClasses); ok {
if unsuccessfulJctx, ok := it.schedulingContext.UnfeasibleSchedulingKeys[schedulingKey]; ok {
jctx := &schedulercontext.JobSchedulingContext{
Created: time.Now(),
ExecutorId: it.schedulingContext.ExecutorId,
JobId: job.GetId(),
Job: job,
UnschedulableReason: unsuccessfulJctx.UnschedulableReason,
PodSchedulingContext: unsuccessfulJctx.PodSchedulingContext,
}
if _, err := it.schedulingContext.AddJobSchedulingContext(jctx); err != nil {
return nil, err
}
continue
}
}
}
gangId, gangCardinality, isGangJob, err := GangIdAndCardinalityFromAnnotations(
job.GetAnnotations(),
)
if err != nil {
// TODO: Get from context passed in.
log := logrus.NewEntry(logrus.New())
logging.WithStacktrace(log, err).Errorf("failed to get gang cardinality for job %s", job.GetId())
gangCardinality = 1 // Schedule jobs with invalid gang cardinality one by one.
}
if isGangJob {
it.jobsByGangId[gangId] = append(it.jobsByGangId[gangId], job)
gang := it.jobsByGangId[gangId]
if len(gang) == gangCardinality {
delete(it.jobsByGangId, gangId)
it.next = schedulercontext.NewGangSchedulingContext(
jobSchedulingContextsFromJobs(
gang,
it.schedulingContext.ExecutorId,
it.schedulingContext.PriorityClasses,
),
)
return it.next, nil
}
} else {
it.next = schedulercontext.NewGangSchedulingContext(
jobSchedulingContextsFromJobs(
[]interfaces.LegacySchedulerJob{job},
it.schedulingContext.ExecutorId,
it.schedulingContext.PriorityClasses,
),
)
return it.next, nil
}
}
}
func (it *QueuedGangIterator) hitLookbackLimit() bool {
if it.maxLookback == 0 {
return false
}
return it.jobsSeen > it.maxLookback
}
// CandidateGangIterator determines which gang to try scheduling next across queues.
// Specifically, it yields the next gang in the queue with smallest fraction of its fair share,
// where the fraction of fair share computation includes the yielded gang.
type CandidateGangIterator struct {
SchedulingContext *schedulercontext.SchedulingContext
// If true, this iterator only yields gangs where all jobs are evicted.
onlyYieldEvicted bool
// For each queue, weight is the inverse of the priority factor.
weightByQueue map[string]float64
// Sum of all weights.
weightSum float64
// Priority queue containing per-queue iterators.
// Determines the order in which queues are processed.
pq QueueCandidateGangIteratorPQ
}
func NewCandidateGangIterator(
sctx *schedulercontext.SchedulingContext,
iteratorsByQueue map[string]*QueuedGangIterator,
) (*CandidateGangIterator, error) {
weightSum := 0.0
weightByQueue := make(map[string]float64)
for queue := range iteratorsByQueue {
qctx := sctx.QueueSchedulingContexts[queue]
if qctx == nil {
return nil, errors.Errorf("no scheduling context for queue %s", queue)
}
weight := 1 / math.Max(qctx.PriorityFactor, 1)
weightByQueue[queue] = weight
weightSum += weight
}
rv := &CandidateGangIterator{
SchedulingContext: sctx,
weightByQueue: weightByQueue,
weightSum: weightSum,
pq: make(QueueCandidateGangIteratorPQ, 0, len(iteratorsByQueue)),
}
for queue, queueIt := range iteratorsByQueue {
if err := rv.pushToPQ(queue, queueIt); err != nil {
return nil, err
}
}
return rv, nil
}
func (it *CandidateGangIterator) pushToPQ(queue string, queueIt *QueuedGangIterator) error {
gctx, err := queueIt.Peek()
if err != nil {
return err
}
if gctx == nil {
return nil
}
totalResourcesForQueue := it.SchedulingContext.QueueSchedulingContexts[queue].AllocatedByPriority
totalResourcesForQueueWithGang := totalResourcesForQueue.AggregateByResource()
totalResourcesForQueueWithGang.Add(gctx.TotalResourceRequests)
fairShare := it.weightByQueue[queue] / it.weightSum
used := ResourceListAsWeightedApproximateFloat64(it.SchedulingContext.ResourceScarcity, totalResourcesForQueueWithGang)
total := math.Max(ResourceListAsWeightedApproximateFloat64(it.SchedulingContext.ResourceScarcity, it.SchedulingContext.TotalResources), 1)
fractionOfFairShare := (used / total) / fairShare
item := &QueueCandidateGangIteratorItem{
queue: queue,
it: queueIt,
v: gctx,
fractionOfFairShare: fractionOfFairShare,
}
heap.Push(&it.pq, item)
return nil
}
func (it *CandidateGangIterator) OnlyYieldEvicted() {
it.onlyYieldEvicted = true
}
func (it *CandidateGangIterator) Next() (*schedulercontext.GangSchedulingContext, error) {
if v, err := it.Peek(); err != nil {
return nil, err
} else {
if err := it.Clear(); err != nil {
return nil, err
}
return v, nil
}
}
func (it *CandidateGangIterator) Clear() error {
if len(it.pq) == 0 {
return nil
}
item := heap.Pop(&it.pq).(*QueueCandidateGangIteratorItem)
if err := item.it.Clear(); err != nil {
return err
}
if err := it.pushToPQ(item.queue, item.it); err != nil {
return err
}
return nil
}
func (it *CandidateGangIterator) Peek() (*schedulercontext.GangSchedulingContext, error) {
// Yield a gang.
// To ensure the last scheduled gang is accounted for,
// pop and push items from/to the pq until we've seen the same queue twice consecutively,
// since at that point we're sure pq priority for that item is correct.
activeQueue := ""
for {
if len(it.pq) == 0 {
// No queued jobs left.
return nil, nil
}
item := heap.Pop(&it.pq).(*QueueCandidateGangIteratorItem)
if item.queue != activeQueue {
activeQueue = item.queue
if err := it.pushToPQ(item.queue, item.it); err != nil {
return nil, err
}
continue
}
gctx := item.v // Cached value is guaranteed to be fresh here.
if it.onlyYieldEvicted && !gctx.AllJobsEvicted {
// We assume here that all evicted jobs appear before non-evicted jobs in the queue.
// Hence, it's safe to drop a queue once a non-evicted job has been seen.
continue
}
if err := it.pushToPQ(item.queue, item.it); err != nil {
return nil, err
}
return gctx, nil
}
}
// Priority queue used by CandidateGangIterator to determine from which queue to schedule the next job.
type QueueCandidateGangIteratorPQ []*QueueCandidateGangIteratorItem
type QueueCandidateGangIteratorItem struct {
// Each item corresponds to a queue.
queue string
// Iterator for this queue.
it *QueuedGangIterator
// Most recent value produced by the iterator.
// Cached here to avoid repeating scheduling checks unnecessarily.
v *schedulercontext.GangSchedulingContext
// Fraction of its fair share this queue would have
// if its next schedulable job were to be scheduled.
fractionOfFairShare float64
// The index of the item in the heap.
// maintained by the heap.Interface methods.
index int
}
func (pq QueueCandidateGangIteratorPQ) Len() int { return len(pq) }
func (pq QueueCandidateGangIteratorPQ) Less(i, j int) bool {
// Tie-break by queue name.
if pq[i].fractionOfFairShare == pq[j].fractionOfFairShare {
return pq[i].queue < pq[j].queue
}
return pq[i].fractionOfFairShare < pq[j].fractionOfFairShare
}
func (pq QueueCandidateGangIteratorPQ) Swap(i, j int) {
pq[i], pq[j] = pq[j], pq[i]
pq[i].index = i
pq[j].index = j
}
func (pq *QueueCandidateGangIteratorPQ) Push(x any) {
n := len(*pq)
item := x.(*QueueCandidateGangIteratorItem)
item.index = n
*pq = append(*pq, item)
}
func (pq *QueueCandidateGangIteratorPQ) Pop() any {
old := *pq
n := len(old)
item := old[n-1]
old[n-1] = nil // avoid memory leak
item.index = -1 // for safety
*pq = old[0 : n-1]
return item
}