58 lines
1.8 KiB
C#
58 lines
1.8 KiB
C#
using System.Collections.Concurrent;
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namespace Monitor.Backend.Application;
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/// <summary>登录限流：每个来源在滑动的一分钟内最多尝试若干次。</summary>
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public sealed class LoginRateLimiter
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{
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private readonly ConcurrentDictionary<string, Queue<long>> _attempts = new();
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private readonly BackendOptions _options;
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private readonly TimeProvider _time;
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public LoginRateLimiter(BackendOptions options, TimeProvider time)
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{
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_options = options;
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_time = time;
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}
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/// <summary>登记一次尝试；超限时返回 false 与建议的重试等待秒数。</summary>
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public bool TryAcquire(string source, out int retryAfterSeconds)
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{
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long now = _time.GetUtcNow().ToUnixTimeMilliseconds();
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Queue<long> queue = _attempts.GetOrAdd(source, _ => new Queue<long>());
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lock (queue)
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{
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while (queue.Count > 0 && now - queue.Peek() >= 60_000)
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{
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queue.Dequeue();
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}
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if (queue.Count >= _options.LoginAttemptsPerMinute)
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{
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retryAfterSeconds = (int)Math.Max(1, (60_000 - (now - queue.Peek()) + 999) / 1000);
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return false;
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}
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queue.Enqueue(now);
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retryAfterSeconds = 0;
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return true;
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}
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}
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/// <summary>清理很久没有尝试的来源，避免字典无限增长。</summary>
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public void Prune()
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{
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long now = _time.GetUtcNow().ToUnixTimeMilliseconds();
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foreach ((string key, Queue<long> queue) in _attempts)
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{
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lock (queue)
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{
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if (queue.Count == 0 || now - queue.Peek() >= 60_000)
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{
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_attempts.TryRemove(key, out _);
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}
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}
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}
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}
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}
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