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priority_queue.go
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priority_queue.go
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package pqueue
import (
"context"
"errors"
"log"
"sync"
"time"
)
type PriorityQueueInterface interface {
WaitUntilInvoked(id string) (*QueueItem, error)
ProcessQueue(requestLimit int64, timeLimit time.Duration, stop chan struct{})
}
type PQueues struct {
SuperUserPQueue *PriorityQueue
UserPQueue *PriorityQueue
}
func NewPQueues() PQueues {
return PQueues{
SuperUserPQueue: NewPriorityQueue().(*PriorityQueue),
UserPQueue: NewPriorityQueue().(*PriorityQueue),
}
}
type PriorityQueue struct {
queueArray []*QueueItem
queueMap sync.Map
}
func NewPriorityQueue() PriorityQueueInterface {
return &PriorityQueue{
queueArray: make([]*QueueItem, 0),
}
}
func (pq *PriorityQueue) Len() int { return len(pq.queueArray) }
func (pq *PriorityQueue) Less(i, j int) bool {
return pq.queueArray[i].Priority > pq.queueArray[j].Priority
}
func (pq *PriorityQueue) Swap(i, j int) {
pq.queueArray[i], pq.queueArray[j] = pq.queueArray[j], pq.queueArray[i]
pq.queueArray[i].index = i
pq.queueArray[j].index = j
}
func (pq *PriorityQueue) Push(x interface{}) {
item := x.(*QueueItem)
pqMapItem, exists := pq.queueMap.Load(item.Id)
if exists {
pqItem, ok := pqMapItem.(*QueueItem)
if !ok {
panic("failed to convert map element")
}
pqItem.Amount++
return
}
n := len(pq.queueArray)
item.index = n
item.invoked = PROCESSING
item.Amount++
pq.queueArray = append(pq.queueArray, item)
pq.queueMap.Store(item.Id, item)
}
func (pq *PriorityQueue) Pop() interface{} {
old := pq.queueArray
n := len(old)
item := old[n-1]
old[n-1] = nil
item.index = -1
pq.queueArray = old[0 : n-1]
pq.queueMap.Delete(item.Id)
return item
}
func (pq *PriorityQueue) RemoveById(id string) error {
item, err := pq.getElement(id)
if err != nil {
return err
}
if item.Amount > 1 {
item.Amount--
return nil
}
pq.queueArray = append(pq.queueArray[:item.index], pq.queueArray[item.index+1:]...)
pq.queueMap.Delete(item.Id)
pq.FixIndexesInPQueue()
return nil
}
func (pq *PriorityQueue) FixIndexesInPQueue() {
for i, queueItem := range pq.queueArray {
if queueItem.index != i {
queueItem.index = i
}
}
}
func (pq *PriorityQueue) getElement(id string) (*QueueItem, error) {
pqMapItem, exists := pq.queueMap.Load(id)
if !exists {
return nil, errors.New("element not found")
}
pqItem, ok := pqMapItem.(*QueueItem)
if !ok {
return nil, errors.New("failed to convert map element")
}
return pqItem, nil
}
func (pq *PriorityQueue) WaitUntilInvoked(id string) (*QueueItem, error) {
log.Printf("waiting until invoked for `%s`", id)
item, err := pq.getElement(id)
if err != nil {
return nil, err
}
item.waitInvoked()
return item, nil
}
func (pq *PriorityQueue) ProcessQueue(requestLimit int64, timeLimit time.Duration, stop chan struct{}) {
ticker := time.NewTicker(timeLimit / time.Duration(requestLimit))
defer ticker.Stop()
for {
select {
case <-ticker.C:
pq.processNextItem()
case <-stop:
return
}
}
}
func (pq *PriorityQueue) processNextItem() {
for i := 0; i < pq.Len(); i++ {
item := pq.queueArray[i]
if item == nil {
continue
}
if item.invoked == INVOKED {
continue
}
item.callFunction()
return
}
}
func PQueuesInstance(ctx context.Context) *PQueues {
return ctx.Value("pqueues").(*PQueues)
}
func CtxPQueues(entry interface{}, ctx context.Context) context.Context {
return context.WithValue(ctx, "pqueues", entry)
}