/// <summary>
/// 1.并发访问只会有一个真正的去请求，其它都在等结果。
/// 2.成功一次后，以后都不会慢，至多数据几秒内不新鲜，因为数据过期后依然返回的是老数据，并且同时开了个线程在拿新数据。
/// </summary>
/// <typeparam name="T"></typeparam>
/// <param name="key"></param>
/// <param name="action"></param>
/// <param name="value"></param>
/// <param name="expireMinutes">更新频率，此设置是用来保证新鲜度的，设置长或短不会影响性能！</param>
/// <returns></returns>
public static T Get <T>(CacheKeys key, Action action, ref T value, int expireMinutes)
{
bool hasError = false;
if (key.NoCache()) //沒數據就嘗試去填充數據
{
var startTime = DateTime.Now;
var isFirst = Queue.TryAdd(key.GetName(), startTime); //第一個進來的填充就行，其它的等結果吧
if (isFirst)
{
Task.Factory.StartNew(() =>
{
try
{
if (key.NoCache())
{
action();
var cacheInfo = new CacheInfo
{
Key = key.GetName(),
Desc = key.GetDescription(),
Count = 1,
CreateTime = DateTime.UtcNow,
ExpireTime = DateTime.UtcNow.AddMinutes(expireMinutes),
BuildTime = (DateTime.Now - startTime)
};
HttpRuntime.Cache.Insert(cacheInfo.Key, cacheInfo, null, cacheInfo.ExpireTime.Value, Cache.NoSlidingExpiration, CacheItemPriority.NotRemovable, CacheOnRemovedCallback);
// PkgHelper.WritePerfLog("CacheHelper", (DateTime.Now - startTime).Milliseconds, key.GetName(), $"items：{1} ", "Offline.Service");
}
}
catch (Exception ex)
{
hasError = true;
var director = AppDomain.CurrentDomain?.BaseDirectory?.ToLower() ?? string.Empty;
if (!string.IsNullOrWhiteSpace(director) && director.Contains("scheduler"))
{
// TASK 报这个错误是正常的，不记日志
}
else
{
}
}
finally
{
Queue.TryRemove(key.GetName(), out startTime);
}
});
}
}
DateTime end = DateTime.Now.AddMinutes(5);
while (DateTime.Now < end)
{
if (value != null || hasError)
{
break;
}
Thread.Sleep(500);
}
return(value);
}
