feat: 实现数据库备份与恢复

server/pkg/queue/delay_queue.go

@@ -0,0 +1,221 @@
+package queue
+
+import (
+	"context"
+	"math"
+	"sync"
+	"time"
+)
+
+const minTimerDelay = time.Millisecond
+const maxTimerDelay = time.Nanosecond * math.MaxInt64
+
+type DelayQueue[T Delayable] struct {
+	enqueuedSignal chan struct{}
+	dequeuedSignal chan struct{}
+	transferChan   chan T
+	singleDequeue  chan struct{}
+	mutex          sync.Mutex
+	priorityQueue  *PriorityQueue[T]
+	elmMap         map[uint64]T
+
+	zero T
+}
+
+type Delayable interface {
+	GetDeadline() time.Time
+	GetId() uint64
+}
+
+func NewDelayQueue[T Delayable](cap int) *DelayQueue[T] {
+	singleDequeue := make(chan struct{}, 1)
+	singleDequeue <- struct{}{}
+	return &DelayQueue[T]{
+		enqueuedSignal: make(chan struct{}),
+		dequeuedSignal: make(chan struct{}),
+		transferChan:   make(chan T),
+		singleDequeue:  singleDequeue,
+		elmMap:         make(map[uint64]T, 64),
+		priorityQueue: NewPriorityQueue[T](cap, func(src T, dst T) bool {
+			return src.GetDeadline().Before(dst.GetDeadline())
+		}),
+	}
+}
+
+func (s *DelayQueue[T]) Dequeue(ctx context.Context) (T, bool) {
+	// 出队锁：避免因重复获取队列头部同一元素降低性能
+	select {
+	case <-s.singleDequeue:
+		defer func() {
+			s.singleDequeue <- struct{}{}
+		}()
+	case <-ctx.Done():
+		return s.zero, false
+	}
+
+	for {
+		// 全局锁：避免入队和出队信号的重置与激活出现并发问题
+		s.mutex.Lock()
+		if ctx.Err() != nil {
+			s.mutex.Unlock()
+			return s.zero, false
+		}
+
+		// 接收直接转发的不需要延迟的新元素
+		select {
+		case elm := <-s.transferChan:
+			delete(s.elmMap, elm.GetId())
+			s.mutex.Unlock()
+			return elm, true
+		default:
+		}
+
+		// 延迟时间缺省值为 maxTimerDelay, 表示队列为空
+		delay := maxTimerDelay
+		if elm, ok := s.priorityQueue.Peek(0); ok {
+			now := time.Now()
+			delay = elm.GetDeadline().Sub(now)
+			if delay < minTimerDelay {
+				// 无需延迟，头部元素出队后直接返回
+				_, _ = s.dequeue()
+				delete(s.elmMap, elm.GetId())
+				s.mutex.Unlock()
+				return elm, ok
+			}
+		}
+		// 重置入队信号，避免历史信号干扰
+		select {
+		case <-s.enqueuedSignal:
+		default:
+		}
+		s.mutex.Unlock()
+
+		if delay == maxTimerDelay {
+			// 队列为空, 等待新元素
+			select {
+			case elm := <-s.transferChan:
+				return elm, true
+			case <-s.enqueuedSignal:
+				continue
+			case <-ctx.Done():
+				return s.zero, false
+			}
+		} else if delay >= minTimerDelay {
+			// 等待时间到期或新元素加入
+			timer := time.NewTimer(delay)
+			select {
+			case elm := <-s.transferChan:
+				return elm, true
+			case <-s.enqueuedSignal:
+				continue
+			case <-timer.C:
+				continue
+			case <-ctx.Done():
+				return s.zero, false
+			}
+		}
+	}
+}
+
+func (s *DelayQueue[T]) dequeue() (T, bool) {
+	elm, ok := s.priorityQueue.Dequeue()
+	if !ok {
+		return s.zero, false
+	}
+	select {
+	case s.dequeuedSignal <- struct{}{}:
+	default:
+	}
+	return elm, true
+}
+
+func (s *DelayQueue[T]) enqueue(val T) bool {
+	if ok := s.priorityQueue.Enqueue(val); !ok {
+		return false
+	}
+	select {
+	case s.enqueuedSignal <- struct{}{}:
+	default:
+	}
+	return true
+}
+
+func (s *DelayQueue[T]) Enqueue(ctx context.Context, val T) bool {
+	for {
+		// 全局锁：避免入队和出队信号的重置与激活出现并发问题
+		s.mutex.Lock()
+		if _, ok := s.elmMap[val.GetId()]; ok {
+			s.mutex.Unlock()
+			return false
+		}
+
+		if ctx.Err() != nil {
+			s.mutex.Unlock()
+			return false
+		}
+
+		// 如果队列未满，入队后直接返回
+		if !s.priorityQueue.IsFull() {
+			s.elmMap[val.GetId()] = val
+			s.enqueue(val)
+			s.mutex.Unlock()
+			return true
+		}
+		// 队列已满，重置出队信号，避免受到历史信号影响
+		select {
+		case <-s.dequeuedSignal:
+		default:
+		}
+		s.mutex.Unlock()
+
+		if delay := val.GetDeadline().Sub(time.Now()); delay >= minTimerDelay {
+			// 新元素需要延迟，等待退出信号、出队信号和到期信号
+			timer := time.NewTimer(delay)
+			select {
+			case <-s.dequeuedSignal:
+				// 收到出队信号，从头开始尝试入队
+				continue
+			case <-timer.C:
+				// 新元素不再需要延迟
+			case <-ctx.Done():
+				return false
+			}
+		} else {
+			// 新元素不需要延迟，等待转发成功信号、出队信号和退出信号
+			select {
+			case s.transferChan <- val:
+				// 新元素转发成功，直接返回（避免队列满且元素未到期导致新元素长时间无法入队）
+				return true
+			case <-s.dequeuedSignal:
+				// 收到出队信号，从头开始尝试入队
+				continue
+			case <-ctx.Done():
+				return false
+			}
+		}
+	}
+}
+
+func (s *DelayQueue[T]) Remove(_ context.Context, elmId uint64) (T, bool) {
+	s.mutex.Lock()
+	defer s.mutex.Unlock()
+
+	if _, ok := s.elmMap[elmId]; ok {
+		delete(s.elmMap, elmId)
+		return s.priorityQueue.Remove(s.index(elmId))
+	}
+	return s.zero, false
+}
+
+func (s *DelayQueue[T]) index(elmId uint64) int {
+	for i := 0; i < s.priorityQueue.Len(); i++ {
+		elm, ok := s.priorityQueue.Peek(i)
+		if !ok {
+			continue
+		}
+		if elmId == elm.GetId() {
+			return i
+		}
+	}
+	return -1
+}