/// <summary>
/// Tries to fetch the result from disk cache, the memory queue, or create it. If the memory queue has space,
/// the writeCallback() will be executed and the resulting bytes put in a queue for writing to disk.
/// If the memory queue is full, writing to disk will be attempted synchronously.
/// In either case, writing to disk can also fail if the disk cache is full and eviction fails.
/// If the memory queue is full, eviction will be done synchronously and can cause other threads to time out
/// while waiting for QueueLock
/// </summary>
/// <param name="key"></param>
/// <param name="dataProviderCallback"></param>
/// <param name="cancellationToken"></param>
/// <param name="retrieveContentType"></param>
/// <returns></returns>
/// <exception cref="OperationCanceledException"></exception>
/// <exception cref="ArgumentOutOfRangeException"></exception>
public async Task <AsyncCacheResult> GetOrCreateBytes(
byte[] key,
AsyncBytesResult dataProviderCallback,
CancellationToken cancellationToken,
bool retrieveContentType)
{
if (cancellationToken.IsCancellationRequested)
{
throw new OperationCanceledException(cancellationToken);
}
var swGetOrCreateBytes = Stopwatch.StartNew();
var entry = new CacheEntry(key, PathBuilder);
// Tell cleanup what we're using
CleanupManager.NotifyUsed(entry);
// Fast path on disk hit
var swFileExists = Stopwatch.StartNew();
var fileBasedResult = await TryGetFileBasedResult(entry, false, retrieveContentType, cancellationToken);
if (fileBasedResult != null)
{
return(fileBasedResult);
}
// Just continue on creating the file. It must have been deleted between the calls
swFileExists.Stop();
var cacheResult = new AsyncCacheResult();
//Looks like a miss. Let's enter a lock for the creation of the file. This is a different locking system
// than for writing to the file
//This prevents two identical requests from duplicating efforts. Different requests don't lock.
//Lock execution using relativePath as the sync basis. Ignore casing differences. This prevents duplicate entries in the write queue and wasted CPU/RAM usage.
var queueLockComplete = await QueueLocks.TryExecuteAsync(entry.StringKey,
Options.WaitForIdenticalRequestsTimeoutMs, cancellationToken,
async() =>
{
var swInsideQueueLock = Stopwatch.StartNew();
// Now, if the item we seek is in the queue, we have a memcached hit.
// If not, we should check the filesystem. It's possible the item has been written to disk already.
// If both are a miss, we should see if there is enough room in the write queue.
// If not, switch to in-thread writing.
var existingQueuedWrite = CurrentWrites.Get(entry.StringKey);
if (existingQueuedWrite != null)
{
cacheResult.Data = existingQueuedWrite.GetReadonlyStream();
cacheResult.ContentType = existingQueuedWrite.ContentType;
cacheResult.Detail = AsyncCacheDetailResult.MemoryHit;
return;
}
if (cancellationToken.IsCancellationRequested)
{
throw new OperationCanceledException(cancellationToken);
}
swFileExists.Start();
// Fast path on disk hit, now that we're in a synchronized state
var fileBasedResult2 = await TryGetFileBasedResult(entry, true, retrieveContentType, cancellationToken);
if (fileBasedResult2 != null)
{
cacheResult = fileBasedResult2;
return;
}
// Just continue on creating the file. It must have been deleted between the calls
swFileExists.Stop();
var swDataCreation = Stopwatch.StartNew();
//Read, resize, process, and encode the image. Lots of exceptions thrown here.
var result = await dataProviderCallback(cancellationToken);
swDataCreation.Stop();
//Create AsyncWrite object to enqueue
var w = new AsyncWrite(entry.StringKey, result.Item2, result.Item1);
cacheResult.Detail = AsyncCacheDetailResult.Miss;
cacheResult.ContentType = w.ContentType;
cacheResult.Data = w.GetReadonlyStream();
// Create a lambda which we can call either in a spawned Task (if enqueued successfully), or
// in this task, if our buffer is full.
async Task <AsyncCacheDetailResult> EvictWriteAndLogUnsynchronized(bool queueFull, TimeSpan dataCreationTime, CancellationToken ct)
{
var delegateStartedAt = DateTime.UtcNow;
var swReserveSpace = Stopwatch.StartNew();
//We only permit eviction proceedings from within the queue or if the queue is disabled
var allowEviction = !queueFull || CurrentWrites.MaxQueueBytes <= 0;
var reserveSpaceResult = await CleanupManager.TryReserveSpace(entry, w.ContentType,
w.GetUsedBytes(), allowEviction, EvictAndWriteLocks, ct);
swReserveSpace.Stop();
var syncString = queueFull ? "synchronous" : "async";
if (!reserveSpaceResult.Success)
{
Logger?.LogError(
queueFull
? "HybridCache synchronous eviction failed; {Message}. Time taken: {1}ms - {2}"
: "HybridCache async eviction failed; {Message}. Time taken: {1}ms - {2}",
syncString, reserveSpaceResult.Message, swReserveSpace.ElapsedMilliseconds,
entry.RelativePath);
return(AsyncCacheDetailResult.CacheEvictionFailed);
}
var swIo = Stopwatch.StartNew();
// We only force an immediate File.Exists check when running from the Queue
// Otherwise it happens inside the lock
var fileWriteResult = await FileWriter.TryWriteFile(entry, delegate(Stream s, CancellationToken ct2)
{
if (ct2.IsCancellationRequested)
{
throw new OperationCanceledException(ct2);
}
var fromStream = w.GetReadonlyStream();
return(fromStream.CopyToAsync(s, 81920, ct2));
}, !queueFull, Options.WaitForIdenticalDiskWritesMs, ct);
swIo.Stop();
var swMarkCreated = Stopwatch.StartNew();
// Mark the file as created so it can be deleted
await CleanupManager.MarkFileCreated(entry,
w.ContentType,
w.GetUsedBytes(),
DateTime.UtcNow);
swMarkCreated.Stop();
switch (fileWriteResult)
{
case CacheFileWriter.FileWriteStatus.LockTimeout:
//We failed to lock the file.
Logger?.LogWarning("HybridCache {Sync} write failed; disk lock timeout exceeded after {IoTime}ms - {Path}",
syncString, swIo.ElapsedMilliseconds, entry.RelativePath);
return(AsyncCacheDetailResult.WriteTimedOut);
case CacheFileWriter.FileWriteStatus.FileAlreadyExists:
Logger?.LogTrace("HybridCache {Sync} write found file already exists in {IoTime}ms, after a {DelayTime}ms delay and {CreationTime}- {Path}",
syncString, swIo.ElapsedMilliseconds,
delegateStartedAt.Subtract(w.JobCreatedAt).TotalMilliseconds,
dataCreationTime, entry.RelativePath);
return(AsyncCacheDetailResult.FileAlreadyExists);
case CacheFileWriter.FileWriteStatus.FileCreated:
if (queueFull)
{
Logger?.LogTrace(@"HybridCache synchronous write complete. Create: {CreateTime}ms. Write {WriteTime}ms. Mark Created: {MarkCreatedTime}ms. Eviction: {EvictionTime}ms - {Path}",
Math.Round(dataCreationTime.TotalMilliseconds).ToString(CultureInfo.InvariantCulture).PadLeft(4),
swIo.ElapsedMilliseconds.ToString().PadLeft(4),
swMarkCreated.ElapsedMilliseconds.ToString().PadLeft(4),
swReserveSpace.ElapsedMilliseconds.ToString().PadLeft(4), entry.RelativePath);
}
else
{
Logger?.LogTrace(@"HybridCache async write complete. Create: {CreateTime}ms. Write {WriteTime}ms. Mark Created: {MarkCreatedTime}ms Eviction {EvictionTime}ms. Delay {DelayTime}ms. - {Path}",
Math.Round(dataCreationTime.TotalMilliseconds).ToString(CultureInfo.InvariantCulture).PadLeft(4),
swIo.ElapsedMilliseconds.ToString().PadLeft(4),
swMarkCreated.ElapsedMilliseconds.ToString().PadLeft(4),
swReserveSpace.ElapsedMilliseconds.ToString().PadLeft(4),
Math.Round(delegateStartedAt.Subtract(w.JobCreatedAt).TotalMilliseconds).ToString(CultureInfo.InvariantCulture).PadLeft(4),
entry.RelativePath);
}
return(AsyncCacheDetailResult.WriteSucceeded);
default:
throw new ArgumentOutOfRangeException();
}
}
async Task <AsyncCacheDetailResult> EvictWriteAndLogSynchronized(bool queueFull,
TimeSpan dataCreationTime, CancellationToken ct)
{
var cacheDetailResult = AsyncCacheDetailResult.Unknown;
var writeLockComplete = await EvictAndWriteLocks.TryExecuteAsync(entry.StringKey,
Options.WaitForIdenticalRequestsTimeoutMs, cancellationToken,
async() =>
{
cacheDetailResult =
await EvictWriteAndLogUnsynchronized(queueFull, dataCreationTime, ct);
});
if (!writeLockComplete)
{
cacheDetailResult = AsyncCacheDetailResult.EvictAndWriteLockTimedOut;
}
return(cacheDetailResult);
}
var swEnqueue = Stopwatch.StartNew();
var queueResult = CurrentWrites.Queue(w, async delegate
{
try
{
var unused = await EvictWriteAndLogSynchronized(false, swDataCreation.Elapsed, CancellationToken.None);
}
catch (Exception ex)
{
Logger?.LogError(ex, "HybridCache failed to flush async write, {Exception} {Path}\n{StackTrace}", ex.ToString(),
entry.RelativePath, ex.StackTrace);
}
});
swEnqueue.Stop();
swInsideQueueLock.Stop();
swGetOrCreateBytes.Stop();
if (queueResult == AsyncWriteCollection.AsyncQueueResult.QueueFull)
{
if (Options.WriteSynchronouslyWhenQueueFull)
{
var writerDelegateResult = await EvictWriteAndLogSynchronized(true, swDataCreation.Elapsed, cancellationToken);
cacheResult.Detail = writerDelegateResult;
}
}
});