private async Task InternalAddOrUpdate(TKey key, CFileSource src, CancellationToken token, ICacheExpirationPolicy policy)
{
//at this point we are not responsible of disposing 'src' cause it's lifetime is wider than this method
var path = await UploadToCacheAsync(src, token);
_entries[key] = new CFileCacheEntry()
{
Created = DateTime.UtcNow,
FilePath = path
}.Pulse(policy);
}
private async Task <CFileCacheEntry> InternalGetOrAdd(TKey key, Func <TKey, Task <CFileSource> > provider, CancellationToken token, ICacheExpirationPolicy policy)
{
CFileCacheEntry cacheEntry;
if (_entries.TryGetValue(key, out cacheEntry))
{
return(cacheEntry.Pulse(policy));
}
//per key mutex required to avoid multiple file upload to cache by same key.
//files are very large objects, so unnecessary actions with them should be avoided if possible.
using (await _perKeyLock.LockAsync(key, token))
{
if (_entries.TryGetValue(key, out cacheEntry))
{
return(cacheEntry.Pulse(policy));
}
token.ThrowIfCancellationRequested();
//we are responsible for creation and disposing of stream we created, so we wrap src in using directive.
using (var src = await provider(key))
{
token.ThrowIfCancellationRequested();
var path = await UploadToCacheAsync(src, token);
cacheEntry = new CFileCacheEntry()
{
Created = DateTime.UtcNow,
FilePath = path
};
//######
_entries[key] = cacheEntry;
return(cacheEntry.Pulse(policy));
}
}
}
