ASP.NET Core使用filter和redis实现接口防重
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背景
日常开发中,经常需要对一些响应不是很快的关键业务接口增加防重功能,即短时间内收到的多个相同的请求,只处理一个,其余不处理,避免产生脏数据。这和幂等性(idempotency)稍微有点区别,幂等性要求的是对重复请求有相同的效果和结果,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
Filter的由来可以追溯到ASP.NET MVC中的ActionFilter和ASP.NET Web API中的ActionFilterAttribute。ASP.NET Core将这些不同类型的Filter统一为一种类型,称为Filter,以简化API和提高灵活性。ASP.NET Core中Filter可以用于实现各种功能,例如身份验证、日志记录、异常处理、性能监控等。
通过使用Filter,我们可以在请求处理管道的特定阶段之前或者之后运行自定义代码,达到AOP的效果。
编码实现
防重组件的思路很简单,将第一次请求的某些参数作为标识符存入redis中,并设置过期时间,下次请求过来,先检查redis相同的请求是否已被处理;
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();
- }
- }
- }
复制代码 PreventDuplicateRequestsActionFilter里,我们首先通过反射从 ActionArguments拿到指定参数字段的值,由于从request body取值略有不同,我们需要分开处理;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
防重组件的全部逻辑在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;
- }
复制代码 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>();
复制代码 使用
假设我们有一个接口CancelOrder,我们指定入参中的OrderId和Reason为因子。- namespace PreventDuplicateRequestDemo.Controllers
- {
- [Route("api/[controller]")]
- [ApiController]
- public class OrderController : ControllerBase
- {
- [HttpPost(nameof(CancelOrder))]
- [PreventDuplicateRequests(5, "OrderId", "Reason")]
- 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; }
- }
- }
复制代码 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
查看redis,已有记录
参考链接
https://learn.microsoft.com/en-us/aspnet/core/mvc/controllers/filters?view=aspnetcore-7.0
https://learn.microsoft.com/en-us/aspnet/core/performance/caching/distributed?view=aspnetcore-7.0
来源:https://www.cnblogs.com/netry/archive/2023/03/15/aspnetcore-prevent-duplicate-requests-filter-redis.html
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发表于 2023-3-15 21:35:24
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