public ImageWorkerResult(ImageCacheMetadata cacheImageMetadata, IImageCacheResolver resolver)
{
this.IsNewOrUpdated = false;
this.SourceImageMetadata = default;
this.CacheImageMetadata = cacheImageMetadata;
this.Resolver = resolver;
}
private async Task ProcessRequestAsync(HttpContext context, bool processRequest, IImageResolver sourceImageResolver, ImageContext imageContext, IDictionary <string, string> commands)
{
// Create a cache key based on all the components of the requested url
string uri = GetUri(context, commands);
string key = this.cacheHash.Create(uri, this.options.CachedNameLength);
ImageMetadata sourceImageMetadata = default;
if (processRequest)
{
// Lock any reads when a write is being done for the same key to prevent potential file locks.
using (await AsyncLock.ReaderLockAsync(key).ConfigureAwait(false))
{
// Check to see if the cache contains this image
sourceImageMetadata = await sourceImageResolver.GetMetaDataAsync().ConfigureAwait(false);
IImageCacheResolver cachedImageResolver = await this.cache.GetAsync(key).ConfigureAwait(false);
if (cachedImageResolver != null)
{
ImageCacheMetadata cachedImageMetadata = await cachedImageResolver.GetMetaDataAsync().ConfigureAwait(false);
if (cachedImageMetadata != default)
{
// Has the cached image expired or has the source image been updated?
if (cachedImageMetadata.SourceLastWriteTimeUtc == sourceImageMetadata.LastWriteTimeUtc &&
cachedImageMetadata.CacheLastWriteTimeUtc > DateTimeOffset.Now.AddDays(-this.options.MaxCacheDays))
{
// We're pulling the image from the cache.
using (Stream cachedBuffer = await cachedImageResolver.OpenReadAsync().ConfigureAwait(false))
{
await this.SendResponseAsync(imageContext, key, cachedBuffer, cachedImageMetadata).ConfigureAwait(false);
}
return;
}
}
}
}
// Not cached? Let's get it from the image resolver.
ChunkedMemoryStream outStream = null;
try
{
if (processRequest)
{
// Enter a write lock which locks writing and any reads for the same request.
// This reduces the overheads of unnecessary processing plus avoids file locks.
using (await AsyncLock.WriterLockAsync(key).ConfigureAwait(false))
{
// No allocations here for inStream since we are passing the raw input stream.
// outStream allocation depends on the memory allocator used.
ImageCacheMetadata cachedImageMetadata = default;
outStream = new ChunkedMemoryStream(this.memoryAllocator);
using (Stream inStream = await sourceImageResolver.OpenReadAsync().ConfigureAwait(false))
using (var image = FormattedImage.Load(this.options.Configuration, inStream))
{
image.Process(this.logger, this.processors, commands);
this.options.OnBeforeSave?.Invoke(image);
image.Save(outStream);
// Check to see if the source metadata has a cachecontrol max-age value and use it to
// override the default max age from our options.
var maxAge = TimeSpan.FromDays(this.options.MaxBrowserCacheDays);
if (!sourceImageMetadata.CacheControlMaxAge.Equals(TimeSpan.MinValue))
{
maxAge = sourceImageMetadata.CacheControlMaxAge;
}
cachedImageMetadata = new ImageCacheMetadata(
sourceImageMetadata.LastWriteTimeUtc,
DateTime.UtcNow,
image.Format.DefaultMimeType,
maxAge);
}
// Allow for any further optimization of the image. Always reset the position just in case.
outStream.Position = 0;
string contentType = cachedImageMetadata.ContentType;
string extension = this.formatUtilities.GetExtensionFromContentType(contentType);
this.options.OnProcessed?.Invoke(new ImageProcessingContext(context, outStream, commands, contentType, extension));
outStream.Position = 0;
// Save the image to the cache and send the response to the caller.
await this.cache.SetAsync(key, outStream, cachedImageMetadata).ConfigureAwait(false);
await this.SendResponseAsync(imageContext, key, outStream, cachedImageMetadata).ConfigureAwait(false);
}
}
}
catch (Exception ex)
{
// Log the error internally then rethrow.
// We don't call next here, the pipeline will automatically handle it
this.logger.LogImageProcessingFailed(imageContext.GetDisplayUrl(), ex);
throw;
}
finally
{
outStream?.Dispose();
}
}
}
private async Task ProcessRequestAsync(
HttpContext context,
IImageResolver sourceImageResolver,
ImageContext imageContext,
IDictionary <string, string> commands)
{
// Create a cache key based on all the components of the requested url
string uri = GetUri(context, commands);
string key = this.cacheHash.Create(uri, this.options.CachedNameLength);
// Check the cache, if present, not out of date and not requiring and update
// we'll simply serve the file from there.
ImageWorkerResult readResult = default;
try
{
readResult = await this.IsNewOrUpdatedAsync(sourceImageResolver, imageContext, key);
}
finally
{
ReadWorkers.TryRemove(key, out Task <ImageWorkerResult> _);
}
if (!readResult.IsNewOrUpdated)
{
await this.SendResponseAsync(imageContext, key, readResult.CacheImageMetadata, readResult.Resolver);
return;
}
// Not cached, or is updated? Let's get it from the image resolver.
var sourceImageMetadata = readResult.SourceImageMetadata;
// Enter an asynchronous write worker which prevents multiple writes and delays any reads for the same request.
// This reduces the overheads of unnecessary processing.
try
{
ImageWorkerResult writeResult = await WriteWorkers.GetOrAddAsync(
key,
async (key) =>
{
RecyclableMemoryStream outStream = null;
try
{
// Prevent a second request from starting a read during write execution.
if (ReadWorkers.TryGetValue(key, out Task <ImageWorkerResult> readWork))
{
await readWork;
}
ImageCacheMetadata cachedImageMetadata = default;
outStream = new RecyclableMemoryStream(this.options.MemoryStreamManager);
IImageFormat format;
// 14.9.3 CacheControl Max-Age
// Check to see if the source metadata has a CacheControl Max-Age value
// and use it to override the default max age from our options.
TimeSpan maxAge = this.options.BrowserMaxAge;
if (!sourceImageMetadata.CacheControlMaxAge.Equals(TimeSpan.MinValue))
{
maxAge = sourceImageMetadata.CacheControlMaxAge;
}
using (Stream inStream = await sourceImageResolver.OpenReadAsync())
{
// No commands? We simply copy the stream across.
if (commands.Count == 0)
{
await inStream.CopyToAsync(outStream);
outStream.Position = 0;
format = await Image.DetectFormatAsync(this.options.Configuration, outStream);
}
else
{
using var image = FormattedImage.Load(this.options.Configuration, inStream);
image.Process(
this.logger,
this.processors,
commands,
this.commandParser,
this.parserCulture);
await this.options.OnBeforeSaveAsync.Invoke(image);
image.Save(outStream);
format = image.Format;
}
}
// Allow for any further optimization of the image.
outStream.Position = 0;
string contentType = format.DefaultMimeType;
string extension = this.formatUtilities.GetExtensionFromContentType(contentType);
await this.options.OnProcessedAsync.Invoke(new ImageProcessingContext(context, outStream, commands, contentType, extension));
outStream.Position = 0;
cachedImageMetadata = new ImageCacheMetadata(
sourceImageMetadata.LastWriteTimeUtc,
DateTime.UtcNow,
contentType,
maxAge,
outStream.Length);
// Save the image to the cache and send the response to the caller.
await this.cache.SetAsync(key, outStream, cachedImageMetadata);
// Remove any resolver from the cache so we always resolve next request
// for the same key.
CacheResolverLru.TryRemove(key);
// Place the resolver in the lru cache.
(IImageCacheResolver ImageCacheResolver, ImageCacheMetadata ImageCacheMetadata)cachedImage = await
CacheResolverLru.GetOrAddAsync(
key,
async k =>
{
IImageCacheResolver resolver = await this.cache.GetAsync(k);
ImageCacheMetadata metadata = default;
if (resolver != null)
{
metadata = await resolver.GetMetaDataAsync();
}
return(resolver, metadata);
});
return(new ImageWorkerResult(cachedImage.ImageCacheMetadata, cachedImage.ImageCacheResolver));
}
catch (Exception ex)
{
// Log the error internally then rethrow.
// We don't call next here, the pipeline will automatically handle it
this.logger.LogImageProcessingFailed(imageContext.GetDisplayUrl(), ex);
throw;
}
finally
{
await this.StreamDisposeAsync(outStream);
}
});
await this.SendResponseAsync(imageContext, key, writeResult.CacheImageMetadata, writeResult.Resolver);
}
finally
{
// As soon as we have sent a response from a writer the result is available from a reader so we remove this task.
// Any existing awaiters will continue to await.
WriteWorkers.TryRemove(key, out Task <ImageWorkerResult> _);
}
}
