/// <summary>
/// Performs key-value loop up in staging area and file cache.
/// Any error manifests itself as a miss, i.e. returns false.
/// </summary>
/// <param name="key">The cache key.</param>
/// <returns>
/// true if the image is found in staging area or File cache,
/// false if not found.
/// </returns>
private bool CheckInStagingAreaAndFileCache(ICacheKey key)
{
EncodedImage result = _stagingArea.Get(key);
if (result != null)
{
result.Dispose();
Debug.WriteLine($"Found image for { key.ToString() } in staging area");
_imageCacheStatsTracker.OnStagingAreaHit();
return(true);
}
else
{
Debug.WriteLine($"Did not find image for { key.ToString() } in staging area");
_imageCacheStatsTracker.OnStagingAreaMiss();
try
{
return(_fileCache.HasKey(key));
}
catch (Exception)
{
return(false);
}
}
}
private Task <EncodedImage> GetAsync(ICacheKey key, AtomicBoolean isCancelled)
{
try
{
if (isCancelled.Value)
{
throw new OperationCanceledException();
}
EncodedImage result = _stagingArea.Get(key);
if (result != null)
{
Debug.WriteLine($"Found image for { key.ToString() } in staging area");
_imageCacheStatsTracker.OnStagingAreaHit();
}
else
{
Debug.WriteLine($"Did not find image for { key.ToString() } in staging area");
_imageCacheStatsTracker.OnStagingAreaMiss();
try
{
IPooledByteBuffer buffer = ReadFromDiskCache(key);
if (buffer == null)
{
return(Task.FromResult(default(EncodedImage)));
}
CloseableReference <IPooledByteBuffer> reference =
CloseableReference <IPooledByteBuffer> .of(buffer);
try
{
result = new EncodedImage(reference);
}
finally
{
CloseableReference <IPooledByteBuffer> .CloseSafely(reference);
}
}
catch (Exception)
{
return(Task.FromResult(default(EncodedImage)));
}
}
return(Task.FromResult(result));
}
catch (Exception)
{
// Log failure
// TODO: 3697790
Debug.WriteLine($"Failed to schedule disk-cache read for { key.ToString() }");
throw;
}
}
/// <summary>
/// Removes the item from the disk cache and the staging area.
/// </summary>
public Task Remove(ICacheKey key)
{
Preconditions.CheckNotNull(key);
_stagingArea.Remove(key);
Task writeTask = default(Task);
_writeToDiskCacheTasks.TryRemove(key, out writeTask);
try
{
return(_writeExecutor.Execute(() =>
{
_stagingArea.Remove(key);
_fileCache.Remove(key);
}));
}
catch (Exception)
{
// Log failure
// TODO: 3697790
Debug.WriteLine($"Failed to schedule disk-cache remove for { key.ToString() }");
throw;
}
}
/// <summary>
/// Writes to disk cache.
/// </summary>
private void WriteToDiskCache(ICacheKey key, EncodedImage encodedImage)
{
Debug.WriteLine($"About to write to disk-cache for key { key.ToString() }");
try
{
_fileCache.Insert(key, new WriterCallbackImpl(os =>
{
_pooledByteStreams.Copy(encodedImage.GetInputStream(), os);
}));
Debug.WriteLine($"Successful disk-cache write for key { key.ToString() }");
}
catch (IOException)
{
// Log failure
// TODO: 3697790
Debug.WriteLine($"Failed to write to disk-cache for key { key.ToString() }");
}
}
/// <summary>
/// Performs disk cache read. In case of any exception null is returned.
/// </summary>
private IPooledByteBuffer ReadFromDiskCache(ICacheKey key)
{
try
{
Debug.WriteLine($"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;
}
}
public async Task AddAsync <TItem>(ICacheKey key, TItem item)
{
_logger.LogTrace($"{TAG} AddAsync called for {key.ToString()}");
if (item == null)
{
return;
}
var cacheOptions = new MemoryCacheEntryOptions();
cacheOptions.SetSlidingExpiration(TimeSpan.FromMinutes(30));
_logger.LogTrace($"{TAG} Adding item to cache.");
await Task.Run(() => _cache.Set(key.Key, item, cacheOptions));
}
private Task <bool> ContainsAsync(ICacheKey key)
{
try
{
return(_readExecutor.Execute(() => CheckInStagingAreaAndFileCache(key)));
}
catch (Exception)
{
// Log failure
// TODO: 3697790
Debug.WriteLine($"Failed to schedule disk-cache read for { key.ToString() }");
throw;
}
}
/// <summary>
/// Associates encodedImage with given key in disk cache.
/// Disk write is performed on background thread, so the
/// caller of this method is not blocked.
/// </summary>
public Task Put(ICacheKey key, EncodedImage encodedImage)
{
Preconditions.CheckNotNull(key);
Preconditions.CheckArgument(EncodedImage.IsValid(encodedImage));
// Store encodedImage in staging area
_stagingArea.Put(key, encodedImage);
// Write to disk cache. This will be executed on background thread,
// so increment the ref count. When this write completes
// (with success/failure), then we will bump down the ref count again.
EncodedImage finalEncodedImage = EncodedImage.CloneOrNull(encodedImage);
try
{
Task writeTask = _writeExecutor.Execute(() =>
{
try
{
WriteToDiskCache(key, finalEncodedImage);
}
finally
{
_stagingArea.Remove(key, finalEncodedImage);
EncodedImage.CloseSafely(finalEncodedImage);
// Removes write task after it's completed.
Task writeTaskCompleted = default(Task);
_writeToDiskCacheTasks.TryRemove(key, out writeTaskCompleted);
}
});
_writeToDiskCacheTasks.TryAdd(key, writeTask);
return(writeTask);
}
catch (Exception)
{
// We failed to enqueue cache write. Log failure and decrement ref count
// TODO: 3697790
Debug.WriteLine($"Failed to schedule disk-cache write for { key.ToString() }");
_stagingArea.Remove(key, encodedImage);
EncodedImage.CloseSafely(finalEncodedImage);
// Removes write task due to error.
Task writeTaskCompleted = default(Task);
_writeToDiskCacheTasks.TryRemove(key, out writeTaskCompleted);
throw;
}
}
private static string SecureHashKey(ICacheKey key)
{
byte[] utf8Bytes = Encoding.UTF8.GetBytes(key.ToString());
return(SecureHashUtil.MakeSHA1HashBase64(utf8Bytes));
}
/// <summary>
/// Determine if an valid entry for the key exists in the staging area.
/// </summary>
public bool ContainsKey(ICacheKey key)
{
lock (_mapGate)
{
Preconditions.CheckNotNull(key);
EncodedImage storedEncodedImage = default(EncodedImage);
if (!_map.TryGetValue(key, out storedEncodedImage))
{
return(false);
}
if (!EncodedImage.IsValid(storedEncodedImage))
{
// Reference is not valid, this means that someone cleared reference
// while it was still in use.
// Log error TODO: 3697790
_map.Remove(key);
Debug.WriteLine($"Found closed reference { storedEncodedImage.GetHashCode() } for key { key.ToString() } ({ key.GetHashCode() })");
return(false);
}
return(true);
}
}
public async Task <TItem> GetAsync <TItem>(ICacheKey key) where TItem : class
{
_logger.LogTrace($"{TAG} GetAsync called for {key.ToString()}");
return(await Task.Run(() => _cache.Get <TItem>(key.Key)));
}
private Task <EncodedImage> FoundPinnedImage(ICacheKey key, EncodedImage pinnedImage)
{
Debug.WriteLine($"Found image for { key.ToString() } in staging area");
_imageCacheStatsTracker.OnStagingAreaHit();
return(Task.FromResult(pinnedImage));
}
