/// <summary>
/// Inserts resource into file with key.
/// </summary>
/// <param name="key">Cache key.</param>
/// <param name="callback">
/// Callback that writes to an output stream.
/// </param>
/// <returns>A sequence of bytes.</returns>
public IBinaryResource Insert(ICacheKey key, IWriterCallback callback)
{
// Write to a temp file, then move it into place.
// This allows more parallelism when writing files.
SettableCacheEvent cacheEvent = SettableCacheEvent.Obtain().SetCacheKey(key);
_cacheEventListener.OnWriteAttempt(cacheEvent);
string resourceId;
lock (_lock)
{
// For multiple resource ids associated with the same image,
// we only write one file
resourceId = CacheKeyUtil.GetFirstResourceId(key);
}
cacheEvent.SetResourceId(resourceId);
try
{
// Getting the file is synchronized
IInserter inserter = StartInsert(resourceId, key);
try
{
inserter.WriteData(callback, key);
// Committing the file is synchronized
IBinaryResource resource = EndInsert(inserter, key, resourceId);
cacheEvent.SetItemSize(resource.GetSize())
.SetCacheSize(_cacheStats.Size);
_cacheEventListener.OnWriteSuccess(cacheEvent);
return(resource);
}
finally
{
if (!inserter.CleanUp())
{
Debug.WriteLine("Failed to delete temp file");
}
}
}
catch (IOException ioe)
{
cacheEvent.SetException(ioe);
_cacheEventListener.OnWriteException(cacheEvent);
Debug.WriteLine("Failed inserting a file into the cache");
throw;
}
finally
{
cacheEvent.Recycle();
}
}
/// <summary>
/// Commits the provided temp file to the cache, renaming it to match
/// the cache's hashing convention.
/// </summary>
private IBinaryResource EndInsert(
IInserter inserter,
ICacheKey key,
string resourceId)
{
lock (_lock)
{
IBinaryResource resource = inserter.Commit(key);
_resourceIndex.Add(resourceId);
_cacheStats.Increment(resource.GetSize(), 1);
return(resource);
}
}
/// <summary>
/// Performs disk cache read. In case of any exception null is returned.
/// </summary>
private IPooledByteBuffer ReadFromDiskCache(ICacheKey key)
{
try
{
Debug.WriteLine($"Disk cache read for { key.ToString() }");
IBinaryResource diskCacheResource = _fileCache.GetResource(key);
if (diskCacheResource == null)
{
Debug.WriteLine($"Disk cache miss for { key.ToString() }");
_imageCacheStatsTracker.OnDiskCacheMiss();
return(null);
}
else
{
Debug.WriteLine($"Found entry in disk cache for { key.ToString() }");
_imageCacheStatsTracker.OnDiskCacheHit();
}
IPooledByteBuffer byteBuffer;
using (Stream inputStream = diskCacheResource.OpenStream())
{
byteBuffer = _pooledByteBufferFactory.NewByteBuffer(
inputStream,
(int)diskCacheResource.GetSize());
}
Debug.WriteLine($"Successful read from disk cache for { key.ToString() }");
return(byteBuffer);
}
catch (Exception)
{
// TODO: 3697790 log failures
// TODO: 5258772 - uncomment line below
// _fileCache.Remove(key);
Debug.WriteLine($"Exception reading from cache for { key.ToString() }");
_imageCacheStatsTracker.OnDiskCacheGetFail();
throw;
}
}