93 lines
1.7 KiB
Go
93 lines
1.7 KiB
Go
package middleware
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import (
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"net/http"
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"sync"
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"time"
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"github.com/gin-gonic/gin"
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)
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type visitor struct {
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tokens float64
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lastSeen time.Time
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}
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// RateLimiter implements a per-IP token bucket rate limiter.
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type RateLimiter struct {
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mu sync.Mutex
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visitors map[string]*visitor
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rate float64 // tokens per second
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burst int // max tokens
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}
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// NewRateLimiter creates a rate limiter.
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// rate is requests per second, burst is max burst size.
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func NewRateLimiter(rate float64, burst int) *RateLimiter {
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rl := &RateLimiter{
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visitors: make(map[string]*visitor),
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rate: rate,
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burst: burst,
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}
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// Cleanup stale entries every 5 minutes
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go func() {
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for {
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time.Sleep(5 * time.Minute)
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rl.cleanup()
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}
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}()
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return rl
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}
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// Limit returns a Gin middleware that enforces the rate limit.
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func (rl *RateLimiter) Limit() gin.HandlerFunc {
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return func(c *gin.Context) {
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ip := c.ClientIP()
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rl.mu.Lock()
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v, exists := rl.visitors[ip]
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now := time.Now()
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if !exists {
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v = &visitor{tokens: float64(rl.burst), lastSeen: now}
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rl.visitors[ip] = v
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}
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// Refill tokens based on elapsed time
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elapsed := now.Sub(v.lastSeen).Seconds()
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v.tokens += elapsed * rl.rate
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if v.tokens > float64(rl.burst) {
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v.tokens = float64(rl.burst)
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}
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v.lastSeen = now
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if v.tokens < 1 {
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rl.mu.Unlock()
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c.Header("Retry-After", "1")
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c.AbortWithStatusJSON(http.StatusTooManyRequests, gin.H{
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"error": "rate limit exceeded",
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})
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return
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}
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v.tokens--
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rl.mu.Unlock()
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c.Next()
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}
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}
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func (rl *RateLimiter) cleanup() {
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rl.mu.Lock()
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defer rl.mu.Unlock()
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cutoff := time.Now().Add(-10 * time.Minute)
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for ip, v := range rl.visitors {
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if v.lastSeen.Before(cutoff) {
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delete(rl.visitors, ip)
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}
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}
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}
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