ASP.NET Core中间件实现限流的代码

public class CounterTest {
    public long timeStamp = getNowTime();
    public int reqCount = 0;
    public final int limit = 100; // 时间窗口内最大请求数
    public final long interval = 1000; // 时间窗口ms

    public boolean grant() {
        long now = getNowTime();
        if (now < timeStamp + interval) {
            // 在时间窗口内
            reqCount++;
            // 判断当前时间窗口内是否超过最大请求控制数
            return reqCount <= limit;
        } else {
            timeStamp = now;
            // 超时后重置
            reqCount = 1;
            return true;
        }
    }

    public long getNowTime() {
        return System.currentTimeMillis();
    }
}

var entry = await _counterStore.GetAsync(counterId, cancellationToken);

if (entry.HasValue)
{
    // entry has not expired
    if (entry.Value.Timestamp + rule.PeriodTimespan.Value >= DateTime.UtcNow)
    {
        // increment request count
        var totalCount = entry.Value.Count + _config.RateIncrementer?.Invoke() ?? 1;
        // deep copy
        counter = new RateLimitCounter
        {
            Timestamp = entry.Value.Timestamp,
            Count = totalCount
        };
    }
}

public class SlidingWindow
{
    private readonly object _syncObject = new object();

    private readonly int _requestIntervalSeconds;
    private readonly int _requestLimit;
    private DateTime _windowStartTime;
    private int _prevRequestCount;
    private int _requestCount;
    public SlidingWindow(int requestLimit, int requestIntervalSeconds)
    {
        _windowStartTime = DateTime.Now;
        _requestLimit = requestLimit;
        _requestIntervalSeconds = requestIntervalSeconds;
    }
    public bool PassRequest()
        lock (_syncObject)
        {
            var currentTime = DateTime.Now;
            var elapsedSeconds = (currentTime - _windowStartTime).TotalSeconds;
            if (elapsedSeconds >= _requestIntervalSeconds * 2)
            {
                _windowStartTime = currentTime;
                _prevRequestCount = 0;
                _requestCount = 0;
                elapsedSeconds = 0;
            }
            else if (elapsedSeconds >= _requestIntervalSeconds)
                _windowStartTime = _windowStartTime.AddSeconds(_requestIntervalSeconds);
                _prevRequestCount = _requestCount;
                elapsedSeconds = (currentTime - _windowStartTime).TotalSeconds;
            } 
            var requestCount = _prevRequestCount * (1 - elapsedSeconds / _requestIntervalSeconds) + _requestCount + 1;
            if (requestCount <= _requestLimit)
                _requestCount++;
                return true;
        }
        return false;
}

public class RateLimitMiddleware : IMiddleware
{
    private readonly SlidingWindow _window;

    public RateLimitMiddleware()
    {
        _window = new SlidingWindow(10, 60);
    }
    public async Task InvokeAsync(HttpContext context, RequestDelegate next)
    {
        if (!_window.PassRequest())
        {
            context.SetEndpoint(new Endpoint((context) =>
            {
                context.Response.StatusCode = StatusCodes.Status403Forbidden;
                return Task.CompletedTask;
            },
                        EndpointMetadataCollection.Empty,
                        "限流"));
        }

        await next(context);
    }
}

services.AddSingleton<RateLimitMiddleware>();