从异步请求返回缓存条目时锁定
本文关键字:锁定 缓存 异步 请求 返回 | 更新日期: 2023-09-27 18:35:24
我写了一个应该从Web服务获取一些信息的方法。我想避免对服务的额外调用,所以我试图根据这篇文章将信息放在 MemoryCache 中。
不同之处在于我在客户端没有"SomeHeavyAndExpensiveComputing",但我将工作委托给Web服务。所以我想等待电话。
据我了解,在当前的实现中,我可能会向 Web 服务器发出多个请求,因为我无法等待锁内的请求,这就是它移出锁的原因。
有没有更好的解决方案?
谢谢。
private static readonly object CompanyInfoLock = new object();
public async Task<CompanyDto> GetCompanyInfo()
{
const string cacheKey = "_COMPANYINFO_";
CompanyDto companyInfo = MemoryCache.Default[cacheKey] as CompanyDto;
if (companyInfo != null) return companyInfo;
CompanyDto company = await _userManagementService.InvokeAsync(x => x.GetCompanyAsync(AppPrincipal.Current.CurrentCompanyId));
lock (CompanyInfoLock)
{
companyInfo = MemoryCache.Default[cacheKey] as CompanyDto;
if (companyInfo != null) return companyInfo;
MemoryCache.Default.Add(cacheKey, company, new CacheItemPolicy
{
SlidingExpiration = new TimeSpan(2, 0, 0)
});
}
return company;
}
使用SemaphoreSlim
,以便在调用 Web 服务之前异步锁定并放置锁定块。
private static readonly SemaphoreSlim CompanyInfoLock = new SemaphoreSlim (1);
public async Task<CompanyDto> GetCompanyInfo()
{
const string cacheKey = "_COMPANYINFO_";
CompanyDto companyInfo;
companyInfo = MemoryCache.Default[cacheKey] as CompanyDto;
if (companyInfo != null) return companyInfo;
await CompanyInfoLock.WaitAsync();
try
{
//Check a 2nd time inside the lock to see if the cache has the data.
companyInfo = MemoryCache.Default[cacheKey] as CompanyDto;
if (companyInfo != null) return companyInfo;
companyInfo = await _userManagementService.InvokeAsync(x => x.GetCompanyAsync(AppPrincipal.Current.CurrentCompanyId));
MemoryCache.Default.Add(cacheKey, companyInfo, new CacheItemPolicy
{
SlidingExpiration = new TimeSpan(2, 0, 0)
});
return companyInfo;
}
finally
{
CompanyInfoLock.Release();
}
}