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4.7 kB · 257 lines
Go
at commit 291cfb87
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import ( "sync" "sync/atomic" "time")
const ( defaultRetentionSeconds int64 = 60 maxRetentionSeconds int64 = 3600 usageSubscriberBuffer = 256 errorSubscriberBuffer = 256
usageSupportRefreshPayload = `{"support_refresh":true}` usageRefreshPayload = `{"refresh":true}`)
type queueItem struct { enqueuedAt time.Time payload []byte}
type queue struct { mu sync.Mutex items []queueItem head int subscribers map[uint64]chan []byte nextSubscriberID uint64}
var ( enabled atomic.Bool retentionSeconds atomic.Int64 global queue errorGlobal queue)
func init() { retentionSeconds.Store(defaultRetentionSeconds)}
func SetEnabled(value bool) { enabled.Store(value) if !value { global.clear() errorGlobal.clear() }}
func Enabled() bool { return enabled.Load()}
func SetRetentionSeconds(value int) { normalized := int64(value) if normalized <= 0 { normalized = defaultRetentionSeconds } else if normalized > maxRetentionSeconds { normalized = maxRetentionSeconds } retentionSeconds.Store(normalized)}
func Enqueue(payload []byte) { if !Enabled() { return } if len(payload) == 0 { return } if global.publishToSubscribers(payload) { return } global.enqueue(payload)}
func EnqueueError(payload []byte) { if !Enabled() { return } if len(payload) == 0 { return } errorGlobal.publishToSubscribers(payload)}
func PopOldest(count int) [][]byte { if !Enabled() { return nil } if count <= 0 { return nil } return global.popOldest(count)}
func SubscribeUsage() (<-chan []byte, func()) { return global.subscribe(usageSubscriberBuffer, []byte(usageSupportRefreshPayload))}
func SubscribeErrors() (<-chan []byte, func()) { return errorGlobal.subscribe(errorSubscriberBuffer, nil)}
func NotifyUsageRefresh() { global.publishToSubscribers([]byte(usageRefreshPayload))}
func (q *queue) clear() { q.mu.Lock()
subscribers := make([]chan []byte, 0, len(q.subscribers)) for _, subscriber := range q.subscribers { subscribers = append(subscribers, subscriber) } q.items = nil q.head = 0 q.subscribers = nil q.mu.Unlock()
for _, subscriber := range subscribers { close(subscriber) }}
func (q *queue) enqueue(payload []byte) { now := time.Now()
q.mu.Lock() defer q.mu.Unlock()
q.pruneLocked(now) q.items = append(q.items, queueItem{ enqueuedAt: now, payload: append([]byte(nil), payload...), }) q.maybeCompactLocked()}
func (q *queue) publishToSubscribers(payload []byte) bool { q.mu.Lock() defer q.mu.Unlock()
if len(q.subscribers) == 0 { return false }
for id, subscriber := range q.subscribers { cloned := append([]byte(nil), payload...) select { case subscriber <- cloned: default: delete(q.subscribers, id) close(subscriber) } }
return true}
func (q *queue) subscribe(buffer int, initialPayload []byte) (<-chan []byte, func()) { subscriber := make(chan []byte, buffer) if len(initialPayload) > 0 { subscriber <- append([]byte(nil), initialPayload...) }
q.mu.Lock() if q.subscribers == nil { q.subscribers = make(map[uint64]chan []byte) } q.nextSubscriberID++ id := q.nextSubscriberID q.subscribers[id] = subscriber q.mu.Unlock()
var once sync.Once unsubscribe := func() { once.Do(func() { q.unsubscribe(id) }) } return subscriber, unsubscribe}
func (q *queue) unsubscribe(id uint64) { q.mu.Lock() subscriber, ok := q.subscribers[id] if ok { delete(q.subscribers, id) } q.mu.Unlock()
if ok { close(subscriber) }}
func (q *queue) popOldest(count int) [][]byte { now := time.Now()
q.mu.Lock() defer q.mu.Unlock()
q.pruneLocked(now) available := len(q.items) - q.head if available <= 0 { q.items = nil q.head = 0 return nil } if count > available { count = available }
out := make([][]byte, 0, count) for i := 0; i < count; i++ { item := q.items[q.head+i] out = append(out, item.payload) } q.head += count q.maybeCompactLocked() return out}
func (q *queue) pruneLocked(now time.Time) { if q.head >= len(q.items) { q.items = nil q.head = 0 return }
windowSeconds := retentionSeconds.Load() if windowSeconds <= 0 { windowSeconds = defaultRetentionSeconds } cutoff := now.Add(-time.Duration(windowSeconds) * time.Second) for q.head < len(q.items) && q.items[q.head].enqueuedAt.Before(cutoff) { q.head++ }}
func (q *queue) maybeCompactLocked() { if q.head == 0 { return } if q.head >= len(q.items) { q.items = nil q.head = 0 return } if q.head < 1024 && q.head*2 < len(q.items) { return } q.items = append([]queueItem(nil), q.items[q.head:]...) q.head = 0}