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可以用于实现例如身份验证、日志记录、异常处理、性能监控等各种功能。
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(); | |
} | |
} | |
} |
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; | |
} |
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; } | |
} | |
} |
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
作者: Clivox
出处: https://www.cnblogs.com/netry/p/aspnetcore-prevent-duplicate-requests-filter-redis.html
本文版权归作者和博客园共有,欢迎转载,但未经作者同意必须保留此段声明,且在文章页面明显位置给出原文链接。
转 https://www.cnblogs.com/netry/p/aspnetcore-prevent-duplicate-requests-filter-redis.html 标签:Core,ASP,string,redis,filter,var,NET,public From: https://www.cnblogs.com/wl-blog/p/17262526.html