mirror of
https://github.com/Rain-kl/OpenFlare.git
synced 2026-09-29 14:06:36 +08:00
ryan
133 lines
2.9 KiB
Go
133 lines
2.9 KiB
Go
// Copyright 2026 Arctel.net
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// SPDX-License-Identifier: Apache-2.0
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// Package limiter provides in-memory rate limiting utilities without external project dependencies.
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package limiter
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import (
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"context"
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"sync"
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"time"
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)
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// Rate specifies a rate limit of Limit events permitted within a Period.
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type Rate struct {
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Limit int
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Period time.Duration
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}
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// Result holds the outcome of an Allow check.
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type Result struct {
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Allowed bool
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Remaining int
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ResetAfter time.Duration
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RetryAfter time.Duration
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}
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type memoryEntry struct {
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timestamps []time.Time
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lastSeen time.Time
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}
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func (e *memoryEntry) prune(cutoff time.Time) {
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validIdx := len(e.timestamps)
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for i, ts := range e.timestamps {
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if ts.After(cutoff) {
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validIdx = i
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break
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}
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}
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if validIdx > 0 && validIdx <= len(e.timestamps) {
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e.timestamps = e.timestamps[validIdx:]
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}
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}
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func (e *memoryEntry) calcBlockedResult(limit int, period time.Duration, now time.Time) *Result {
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currentCount := len(e.timestamps)
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if currentCount == 0 {
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return &Result{
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Allowed: false,
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Remaining: limit,
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ResetAfter: period,
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RetryAfter: 0,
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}
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}
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oldest := e.timestamps[0]
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retryAfter := max(0, oldest.Add(period).Sub(now))
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newest := e.timestamps[currentCount-1]
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resetAfter := max(0, newest.Add(period).Sub(now))
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return &Result{
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Allowed: false,
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Remaining: limit - currentCount,
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ResetAfter: resetAfter,
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RetryAfter: retryAfter,
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}
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}
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// MemoryLimiter implements an in-memory sliding window rate limiter.
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type MemoryLimiter struct {
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mu sync.Mutex
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entries map[string]*memoryEntry
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}
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// NewMemoryLimiter creates a new in-memory rate limiter.
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func NewMemoryLimiter() *MemoryLimiter {
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return &MemoryLimiter{
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entries: make(map[string]*memoryEntry),
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}
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}
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// Allow checks whether 1 event for key is permitted under rate.
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func (m *MemoryLimiter) Allow(ctx context.Context, key string, rate Rate) (*Result, error) {
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return m.AllowN(ctx, key, rate, 1)
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}
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// AllowN checks whether n events for key are permitted under rate.
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func (m *MemoryLimiter) AllowN(_ context.Context, key string, rate Rate, n int) (*Result, error) {
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if rate.Limit <= 0 || rate.Period <= 0 || n <= 0 {
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return &Result{Allowed: true}, nil
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}
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m.mu.Lock()
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defer m.mu.Unlock()
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now := time.Now()
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cutoff := now.Add(-rate.Period)
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entry, ok := m.entries[key]
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if !ok {
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entry = &memoryEntry{}
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m.entries[key] = entry
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}
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entry.lastSeen = now
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entry.prune(cutoff)
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if len(entry.timestamps)+n > rate.Limit {
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return entry.calcBlockedResult(rate.Limit, rate.Period, now), nil
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}
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for i := 0; i < n; i++ {
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entry.timestamps = append(entry.timestamps, now)
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}
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remaining := max(0, rate.Limit-len(entry.timestamps))
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return &Result{
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Allowed: true,
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Remaining: remaining,
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ResetAfter: rate.Period,
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RetryAfter: 0,
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}, nil
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}
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// Reset clears rate limit state for key.
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func (m *MemoryLimiter) Reset(_ context.Context, key string) error {
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m.mu.Lock()
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defer m.mu.Unlock()
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delete(m.entries, key)
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return nil
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}
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