/// <summary>
/// CacheAsideAsync
/// </summary>
/// <param name="cacheItem"></param>
/// <param name="dbRetrieve"></param>
/// <param name="cache"></param>
/// <param name="memoryLockManager"></param>
/// <param name="database"></param>
/// <param name="logger"></param>
/// <returns></returns>
/// <exception cref="CacheException"></exception>
/// <exception cref="RepositoryException"></exception>
public static async Task <TResult?> CacheAsideAsync <TResult>(
CachedItem <TResult> cacheItem, Func <IDatabaseReader, Task <TResult> > dbRetrieve,
ICache cache, IMemoryLockManager memoryLockManager, IDatabase database, ILogger logger)
where TResult : class
{
//Cache First
TResult?result = await cacheItem.GetFromAsync(cache).ConfigureAwait(false);
if (result != null)
{
return(result);
}
using var @lock = memoryLockManager.Lock(cacheItem.ResourceType, cacheItem.CacheKey, Consts.OccupiedTime, Consts.PatienceTime);
if (@lock.IsAcquired)
{
//Double Check
result = await cacheItem.GetFromAsync(cache).ConfigureAwait(false);
if (result != null)
{
return(result);
}
TResult dbRt = await dbRetrieve(database).ConfigureAwait(false);
UtcNowTicks now = TimeUtil.UtcNowTicks;
// 如果TResult是集合类型，可能会存入空集合。而在EntityCache中是不会存入空集合的。
//这样设计是合理的，因为EntityCache是按Entity角度，存入的Entity会复用，就像一个KVStore一样，而CachedItem纯粹是一个查询结果，不思考查询结果的内容。
if (dbRt != null)
{
UpdateCache(cacheItem.Value(dbRt).Timestamp(now), cache);
logger.LogInformation($"缓存 Missed. Entity:{cacheItem.GetType().Name}, CacheKey:{cacheItem.CacheKey}");
}
else
{
logger.LogInformation($"查询到空值. Entity:{cacheItem.GetType().Name}, CacheKey:{cacheItem.CacheKey}");
}
return(dbRt);
}
else
{
logger.LogCritical($"锁未能占用. Entity:{cacheItem.GetType().Name}, CacheKey:{cacheItem.CacheKey}, Lock Status:{@lock.Status}");
return(await dbRetrieve(database).ConfigureAwait(false));
}
}
/// <summary>
/// UpdateCache
/// </summary>
/// <param name="cacheItem"></param>
/// <param name="cache"></param>
/// <exception cref="CacheException"></exception>
private static void UpdateCache <TResult>(CachedItem <TResult> cacheItem, ICache cache) where TResult : class
{
cacheItem.SetToAsync(cache).Fire();
}
/// <summary>
/// InvalidateCache
/// </summary>
/// <param name="cacheItem"></param>
/// <param name="cache"></param>
/// <exception cref="CacheException">Ignore.</exception>
public static void InvalidateCache <TResult>(CachedItem <TResult> cacheItem, ICache cache) where TResult : class
{
cacheItem.RemoveFromAsync(cache).Fire();
}