feat: 添加过载保护、背压和熔断机制

internal/scheduler/circuit_breaker.go

@@ -0,0 +1,145 @@
+package scheduler
+
+import (
+	"sync"
+	"time"
+)
+
+// CircuitBreaker implements a sliding-window circuit breaker for adapter health.
+type CircuitBreaker struct {
+	mu                sync.Mutex
+	errorRateThreshold float64
+	minRequests       int
+	windowSeconds     int
+	openDuration      time.Duration
+	halfOpenMax       int
+
+	// sliding window state
+	requests  []time.Time
+	errors   []time.Time
+
+	// breaker state
+	state       breakerState
+	openedAt    time.Time
+	halfOpenCount int
+}
+
+type breakerState int
+
+const (
+	breakerClosed   breakerState = iota
+	breakerOpen
+	breakerHalfOpen
+)
+
+// NewCircuitBreaker creates a new circuit breaker from config.
+func NewCircuitBreaker(errorRate float64, minRequests, windowSec, openSec, halfOpenMax int) *CircuitBreaker {
+	return &CircuitBreaker{
+		errorRateThreshold: errorRate,
+		minRequests:        minRequests,
+		windowSeconds:      windowSec,
+		openDuration:       time.Duration(openSec) * time.Second,
+		halfOpenMax:        halfOpenMax,
+		state:              breakerClosed,
+	}
+}
+
+// AllowRequest checks if a request should be allowed through.
+func (cb *CircuitBreaker) AllowRequest() bool {
+	cb.mu.Lock()
+	defer cb.mu.Unlock()
+
+	now := time.Now()
+	cb.prune(now)
+
+	switch cb.state {
+	case breakerClosed:
+		return true
+	case breakerOpen:
+		if now.Sub(cb.openedAt) >= cb.openDuration {
+			cb.state = breakerHalfOpen
+			cb.halfOpenCount = 0
+			return true
+		}
+		return false
+	case breakerHalfOpen:
+		if cb.halfOpenCount < cb.halfOpenMax {
+			cb.halfOpenCount++
+			return true
+		}
+		return false
+	}
+	return true
+}
+
+// RecordSuccess records a successful request.
+func (cb *CircuitBreaker) RecordSuccess() {
+	cb.mu.Lock()
+	defer cb.mu.Unlock()
+
+	now := time.Now()
+	cb.requests = append(cb.requests, now)
+
+	if cb.state == breakerHalfOpen {
+		cb.state = breakerClosed
+		cb.requests = nil
+		cb.errors = nil
+	}
+}
+
+// RecordError records a failed request and may trip the breaker.
+func (cb *CircuitBreaker) RecordError() {
+	cb.mu.Lock()
+	defer cb.mu.Unlock()
+
+	now := time.Now()
+	cb.requests = append(cb.requests, now)
+	cb.errors = append(cb.errors, now)
+
+	if cb.state == breakerHalfOpen {
+		cb.state = breakerOpen
+		cb.openedAt = now
+		return
+	}
+
+	if cb.state == breakerClosed && len(cb.requests) >= cb.minRequests {
+		errorRate := float64(len(cb.errors)) / float64(len(cb.requests))
+		if errorRate >= cb.errorRateThreshold {
+			cb.state = breakerOpen
+			cb.openedAt = now
+		}
+	}
+}
+
+// State returns the current breaker state name.
+func (cb *CircuitBreaker) State() string {
+	cb.mu.Lock()
+	defer cb.mu.Unlock()
+	switch cb.state {
+	case breakerClosed:
+		return "closed"
+	case breakerOpen:
+		return "open"
+	case breakerHalfOpen:
+		return "half_open"
+	}
+	return "unknown"
+}
+
+// prune removes entries outside the sliding window.
+func (cb *CircuitBreaker) prune(now time.Time) {
+	cutoff := now.Add(-time.Duration(cb.windowSeconds) * time.Second)
+	cb.requests = pruneBefore(cb.requests, cutoff)
+	cb.errors = pruneBefore(cb.errors, cutoff)
+}
+
+func pruneBefore(times []time.Time, cutoff time.Time) []time.Time {
+	idx := 0
+	for idx < len(times) && times[idx].Before(cutoff) {
+		idx++
+	}
+	if idx > 0 {
+		times = times[idx:]
+	}
+	return times
+}