ASP.NET Core使用filter和redis实现接口防重

背景

效果和结果，通常需要在接口内部执行业务操作前检查状态；而防重可以认为是一个业务无关的通用功能，在ASP.NET Core中我们可以借助过Filter和redis实现。

关于Filter

编码实现

作为一个通用组件，我们需要能让使用者自定义作为标识符的字段以及过期时间，下面开始实现。

PreventDuplicateRequestsActionFilter

public class PreventDuplicateRequestsActionFilter : IAsyncActionFilter
{
    public string[] FactorNames { get; set; }
    public TimeSpan? AbsoluteExpirationRelativeToNow { get; set; }

    private readonly IDistributedCache _cache;
    private readonly ILogger<PreventDuplicateRequestsActionFilter> _logger;

    public PreventDuplicateRequestsActionFilter(IDistributedCache cache, ILogger<PreventDuplicateRequestsActionFilter> logger
    {
        _cache = cache;
        _logger = logger;
    }

    public async Task OnActionExecutionAsync(ActionExecutingContext context, ActionExecutionDelegate next
    {
        var factorValues = new string?[FactorNames.Length];

        var isFromBody =
            context.ActionDescriptor.Parameters.Any(r => r.BindingInfo?.BindingSource == BindingSource.Body;
        if (isFromBody
        {
            var parameterValue = context.ActionArguments.FirstOrDefault(.Value;
            factorValues = FactorNames.Select(name =>
                parameterValue?.GetType(.GetProperty(name?.GetValue(parameterValue?.ToString(.ToArray(;
        }
        else
        {
            for (var index = 0; index < FactorNames.Length; index++
            {
                if (context.ActionArguments.TryGetValue(FactorNames[index], out var factorValue
                {
                    factorValues[index] = factorValue?.ToString(;
                }
            }
        }

        if (factorValues.All(string.IsNullOrEmpty
        {
            _logger.LogWarning("Please config FactorNames.";

            await next(;
            return;
        }

        var idempotentKey = $"{context.HttpContext.Request.Path.Value}:{string.Join("-", factorValues}";
        var idempotentValue = await  _cache.GetStringAsync(idempotentKey;
        if (idempotentValue != null
        {
            _logger.LogWarning("Received duplicate request({},{}, short-circuiting...", idempotentKey, idempotentValue;
            context.Result = new AcceptedResult(;
        }
        else
        {
            await _cache.SetStringAsync(idempotentKey, DateTimeOffset.UtcNow.ToString(,
                new DistributedCacheEntryOptions {AbsoluteExpirationRelativeToNow = AbsoluteExpirationRelativeToNow};
            await next(;
        }
    }
}

PreventDuplicateRequestsActionFilter里，我们首先从通过反射从 ActionArguments拿到指定参数字段的值，由于从request body取值略有不同，我们需要放开处理；接下来开始拼接key并检查redis，如果key已经存在，我们需要短路请求，这里直接返回的是 Accepted (202而不是Conflict (409或者其它错误状态，是为了避免上游已经调用失败而继续重试。

PreventDuplicateRequestsAttribute

PreventDuplicateRequestsActionFilter中已经实现，由于它需要注入 IDistributedCache和ILogger对象，我们使用IFilterFactory实现一个自定义属性，方便使用。

[AttributeUsage(AttributeTargets.Method]
public class PreventDuplicateRequestsAttribute : Attribute, IFilterFactory
{
    private readonly string[] _factorNames;
    private readonly int _expiredMinutes;

    public PreventDuplicateRequestsAttribute(int expiredMinutes, params string[] factorNames
    {
        _expiredMinutes = expiredMinutes;
        _factorNames = factorNames;
    }

    public IFilterMetadata CreateInstance(IServiceProvider serviceProvider
    {
        var filter = serviceProvider.GetService<PreventDuplicateRequestsActionFilter>(;
        filter.FactorNames = _factorNames;
        filter.AbsoluteExpirationRelativeToNow = TimeSpan.FromMinutes(_expiredMinutes;
        return filter;
    }
    public bool IsReusable => false;
}

注册

为了简单，操作redis，直接使用微软Microsoft.Extensions.Caching.StackExchangeRedis包；注册PreventDuplicateRequestsActionFilter，PreventDuplicateRequestsAttribute无需注册。

builder.Services.AddStackExchangeRedisCache(options =>
{
    options.Configuration = "127.0.0.1:6379,DefaultDatabase=1";
};
builder.Services.AddScoped<PreventDuplicateRequestsActionFilter>(;

使用

假设我们有一个接口CancelOrder，我们指定入参中的OrderId为防重因子。

namespace PreventDuplicateRequestDemo.Controllers
{
    [Route("api/[controller]"]
    [ApiController]
    public class OrderController : ControllerBase
    {
        [HttpPost(nameof(CancelOrder]
        [PreventDuplicateRequests(5, "OrderId"]
        public async Task<IActionResult> CancelOrder([FromBody] CancelOrderRequest request
        {
            await Task.Delay(1000;
            return new OkResult(;
        }
    }

    public class CancelOrderRequest
    {
        public Guid OrderId { get; set; }
        public string reason { get; set; }
    }
}

启动程序，多次调用api，除第一次调用成功，其余请求皆被短路

参考链接

https://learn.microsoft.com/en-us/aspnet/core/performance/caching/distributed?view=aspnetcore-7.0

编程笔记 » ASP.NET Core使用filter和redis实现接口防重