[#9999] quota: Add limiter

Signed-off-by: Dmitrii Stepanov <d.stepanov@yadro.com>

pkg/core/quota/limiter.go

@@ -0,0 +1,292 @@
+package quota
+
+import (
+	"container/heap"
+	"context"
+	"fmt"
+	"math/rand/v2"
+	"sync"
+	"sync/atomic"
+)
+
+type Quota struct {
+	Read  int64
+	Write int64
+}
+
+type Priority struct {
+	Class string
+	Value byte
+}
+
+type Release func()
+
+type limit struct {
+	read, write       int64
+	maxRead, maxWrite int64
+}
+
+type queueItem struct {
+	priority byte
+	ts       uint64
+	index    int
+}
+
+type queue struct {
+	l     *limit
+	w     int32
+	items []*queueItem
+}
+
+type QuotaLimiter struct {
+	l         *limit
+	classes   map[string]*queue
+	queues    []*queue
+	nextQueue *queue
+	cond      *sync.Cond
+	ts        *atomic.Uint64
+}
+
+func (ql *QuotaLimiter) Acquire(ctx context.Context, p Priority, q Quota) (Release, error) {
+	queue, ok := ql.classes[p.Class]
+	if !ok {
+		return nil, fmt.Errorf("unknown class '%s'", p.Class)
+	}
+
+	if ql.l.maxRead > 0 && q.Read > ql.l.maxRead {
+		return nil, fmt.Errorf("read quota %d exceeds total limit %d", q.Read, ql.l.maxRead)
+	}
+
+	if ql.l.maxWrite > 0 && q.Write > ql.l.maxWrite {
+		return nil, fmt.Errorf("read quota %d exceeds total limit %d", q.Write, ql.l.maxWrite)
+	}
+
+	if queue.l.maxRead > 0 && q.Read > queue.l.maxRead {
+		return nil, fmt.Errorf("read quota %d exceeds queue limit %d", q.Read, queue.l.maxRead)
+	}
+
+	if queue.l.maxWrite > 0 && q.Write > queue.l.maxWrite {
+		return nil, fmt.Errorf("read quota %d exceeds queue limit %d", q.Write, queue.l.maxWrite)
+	}
+
+	ts := ql.ts.Add(1)
+
+	ql.cond.L.Lock()
+	defer ql.cond.L.Unlock()
+
+	stop := context.AfterFunc(ctx, func() {
+		ql.cond.Broadcast()
+	})
+	defer stop()
+
+	allow := ql.nextQueue == nil && // no scheduled queue
+		hasQuota(q, queue.l) && // queue limit
+		hasQuota(q, ql.l) // global lomit
+
+	if allow {
+		applyQuota(q, queue.l)
+		applyQuota(q, ql.l)
+		return func() { ql.release(p, q) }, nil
+	}
+
+	qi := &queueItem{
+		priority: p.Value,
+		ts:       ts,
+	}
+
+	queue.push(qi)
+	if queue.count() == 1 {
+		ql.resetNextQueue()
+	}
+
+	var hasGlobalQuota, hasQueueQuota, isNextItem bool
+	for !allow {
+		ql.cond.Wait()
+
+		if err := ctx.Err(); err != nil {
+			queue.drop(qi)
+			if queue.count() == 0 {
+				ql.resetNextQueue()
+			}
+			return nil, ctx.Err()
+		}
+
+		hasGlobalQuota = hasQuota(q, ql.l)
+		hasQueueQuota = hasQuota(q, queue.l)
+		isNextItem = ql.nextQueue == queue && queue.top() == qi
+
+		if hasGlobalQuota && !hasQueueQuota && isNextItem {
+			ql.changeNextQueue()
+		}
+		allow = hasGlobalQuota && hasQueueQuota && isNextItem
+	}
+
+	applyQuota(q, queue.l)
+	applyQuota(q, ql.l)
+	queue.pop()
+	ql.resetNextQueue()
+	return func() { ql.release(p, q) }, nil
+}
+
+func (ql *QuotaLimiter) release(p Priority, q Quota) {
+	queue, ok := ql.classes[p.Class]
+	if !ok {
+		panic("unknown class " + p.Class)
+	}
+
+	ql.cond.L.Lock()
+	defer ql.cond.L.Unlock()
+
+	releaseQuota(q, queue.l)
+	releaseQuota(q, ql.l)
+
+	ql.cond.Broadcast()
+}
+
+func (ql *QuotaLimiter) resetNextQueue() {
+	var nonEmptyQueues []*queue
+	var totalWeight int64
+	for _, q := range ql.queues {
+		if q.count() > 0 {
+			nonEmptyQueues = append(nonEmptyQueues, q)
+			totalWeight += int64(q.weight())
+		}
+	}
+	if len(nonEmptyQueues) == 0 {
+		ql.nextQueue = nil
+		return
+	}
+	ql.selectNextQueue(nonEmptyQueues, totalWeight)
+}
+
+func (ql *QuotaLimiter) changeNextQueue() {
+	var nonEmptyQueues []*queue
+	var totalWeight int64
+	for _, q := range ql.queues {
+		if q.count() > 0 && q != ql.nextQueue {
+			nonEmptyQueues = append(nonEmptyQueues, q)
+			totalWeight += int64(q.weight())
+		}
+	}
+	if len(nonEmptyQueues) == 0 {
+		return
+	}
+	ql.selectNextQueue(nonEmptyQueues, totalWeight)
+}
+
+func (ql *QuotaLimiter) selectNextQueue(nonEmptyQueues []*queue, totalWeight int64) {
+	if totalWeight == 0 {
+		ql.nextQueue = nonEmptyQueues[rand.IntN(len(nonEmptyQueues))]
+		return
+	}
+	weight := rand.Int64N(totalWeight)
+	var low, up int64
+	for _, q := range nonEmptyQueues {
+		low = up
+		up += int64(q.weight())
+		if weight >= low && weight < up {
+			ql.nextQueue = q
+			return
+		}
+	}
+	panic("undefined next queue")
+}
+
+func hasQuota(q Quota, l *limit) bool {
+	if q.Read > 0 && l.maxRead > 0 && q.Read+l.read > l.maxRead {
+		return false
+	}
+	if q.Write > 0 && l.maxWrite > 0 && q.Write+l.write > l.write {
+		return false
+	}
+	return true
+}
+
+func applyQuota(q Quota, l *limit) {
+	if q.Read > 0 && l.maxRead > 0 {
+		l.read += q.Read
+	}
+	if q.Write > 0 && l.maxWrite > 0 {
+		l.write += q.Write
+	}
+}
+
+func releaseQuota(q Quota, l *limit) {
+	if q.Read > 0 && l.maxRead > 0 {
+		l.read -= q.Read
+		if l.read < 0 {
+			panic("invalid read limit after release")
+		}
+	}
+	if q.Write > 0 && l.maxWrite > 0 {
+		l.write -= q.Write
+		if l.write < 0 {
+			panic("invalid write limit after release")
+		}
+	}
+}
+
+func (q *queue) push(qi *queueItem) {
+	heap.Push(q, qi)
+}
+
+func (q *queue) pop() {
+	heap.Pop(q)
+}
+
+func (q *queue) drop(qi *queueItem) {
+	heap.Remove(q, qi.index)
+}
+
+func (q *queue) top() *queueItem {
+	if len(q.items) > 0 {
+		return q.items[0]
+	}
+
+	return nil
+}
+
+func (q *queue) count() int {
+	return len(q.items)
+}
+
+func (q *queue) weight() int32 {
+	return q.w
+}
+
+// Len implements heap.Interface.
+func (q *queue) Len() int {
+	return q.count()
+}
+
+// Less implements heap.Interface.
+func (q *queue) Less(i int, j int) bool {
+	if q.items[i].priority == q.items[j].priority {
+		return q.items[i].ts < q.items[j].ts
+	}
+	return q.items[i].priority > q.items[j].priority
+}
+
+// Pop implements heap.Interface.
+func (q *queue) Pop() any {
+	n := len(q.items)
+	item := q.items[n-1]
+	q.items[n-1] = nil
+	q.items = q.items[0 : n-1]
+	item.index = -1
+	return item
+}
+
+// Push implements heap.Interface.
+func (q *queue) Push(x any) {
+	it := x.(*queueItem)
+	it.index = q.Len()
+	q.items = append(q.items, it)
+}
+
+// Swap implements heap.Interface.
+func (q *queue) Swap(i int, j int) {
+	q.items[i], q.items[j] = q.items[j], q.items[i]
+	q.items[i].index = i
+	q.items[j].index = j
+}

pkg/core/quota/limiter_test.go

@@ -0,0 +1,100 @@
+package quota
+
+import (
+	"math/rand/v2"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestQueue(t *testing.T) {
+	t.Run("different priority", func(t *testing.T) {
+		q := &queue{}
+		const count = 12345
+		for i := range count {
+			priority := i % 256
+			q.push(&queueItem{
+				priority: byte(priority),
+			})
+		}
+		testQueueInvariant(t, q)
+	})
+	t.Run("same priority, different ts, inc", func(t *testing.T) {
+		q := &queue{}
+		var ts uint64
+		const count = 10000
+		for range count {
+			q.push(&queueItem{
+				priority: 100,
+				ts:       ts,
+			})
+			ts++
+		}
+		testQueueInvariant(t, q)
+	})
+	t.Run("same priority, different ts, dec", func(t *testing.T) {
+		q := &queue{}
+
+		const count = 10000
+		ts := uint64(count)
+		for range count {
+			q.push(&queueItem{
+				priority: 100,
+				ts:       ts,
+			})
+			ts--
+		}
+		testQueueInvariant(t, q)
+	})
+	t.Run("drop, inc", func(t *testing.T) {
+		q := &queue{}
+		var ts uint64
+		const count = 12345
+		for i := range count {
+			q.push(&queueItem{
+				priority: byte(i % 256),
+				ts:       ts,
+			})
+			ts++
+		}
+		for q.Len() > 0 {
+			idx := rand.IntN(q.count())
+			it := q.items[idx]
+			q.drop(it)
+			testQueueInvariant(t, q)
+		}
+	})
+	t.Run("drop, dec", func(t *testing.T) {
+		q := &queue{}
+		const count = 12345
+		ts := uint64(count)
+		for i := range count {
+			q.push(&queueItem{
+				priority: byte(i % 256),
+				ts:       ts,
+			})
+			ts--
+		}
+		for q.Len() > 0 {
+			idx := rand.IntN(q.count())
+			it := q.items[idx]
+			q.drop(it)
+			testQueueInvariant(t, q)
+		}
+	})
+}
+
+func testQueueInvariant(t *testing.T, q *queue) {
+	var previous *queueItem
+	for q.count() > 0 {
+		current := q.top()
+		if previous != nil {
+			require.True(t, previous.priority > current.priority ||
+				(previous.priority == current.priority &&
+					(previous.ts == current.ts || previous.ts < current.ts)))
+		}
+		previous = current
+		q.pop()
+	}
+	require.Equal(t, 0, q.count())
+}