Semaphore for image resizing.

backend/src/Squidex.Infrastructure/Assets/ImageSharp/ImageSharpAssetThumbnailGenerator.cs

@@ -7,6 +7,7 @@
 
 using System;
 using System.IO;
+using System.Threading;
 using System.Threading.Tasks;
 using SixLabors.ImageSharp;
 using SixLabors.ImageSharp.Formats.Jpeg;
@@ -19,20 +20,28 @@ namespace Squidex.Infrastructure.Assets.ImageSharp
 {
     public sealed class ImageSharpAssetThumbnailGenerator : IAssetThumbnailGenerator
     {
-        public Task CreateThumbnailAsync(Stream source, Stream destination, ResizeOptions options)
+        private readonly SemaphoreSlim semaphoreSlim = new SemaphoreSlim(Math.Max(Environment.ProcessorCount / 4, 1));
+
+        public async Task CreateThumbnailAsync(Stream source, Stream destination, ResizeOptions options)
         {
+            Guard.NotNull(source, nameof(source));
+            Guard.NotNull(destination, nameof(destination));
             Guard.NotNull(options, nameof(options));
 
             if (!options.IsValid)
             {
                 source.CopyTo(destination);
 
-                return Task.CompletedTask;
+                return;
             }
 
             var w = options.Width ?? 0;
             var h = options.Height ?? 0;
 
+            await semaphoreSlim.WaitAsync();
+
+            try
+            {
                 using (var image = Image.Load(source, out var format))
                 {
                     var encoder = Configuration.Default.ImageFormatsManager.FindEncoder(format);
@@ -83,12 +92,17 @@ namespace Squidex.Infrastructure.Assets.ImageSharp
 
                     image.Save(destination, encoder);
                 }
-
+            }
-            return Task.CompletedTask;
+            finally
+            {
+                semaphoreSlim.Release();
+            }
         }
 
         public Task<ImageInfo?> GetImageInfoAsync(Stream source)
         {
+            Guard.NotNull(source, nameof(source));
+
             ImageInfo? result = null;
 
             try
@@ -108,7 +122,14 @@ namespace Squidex.Infrastructure.Assets.ImageSharp
             return Task.FromResult(result);
         }
 
-        public Task<ImageInfo> FixOrientationAsync(Stream source, Stream destination)
+        public async Task<ImageInfo> FixOrientationAsync(Stream source, Stream destination)
+        {
+            Guard.NotNull(source, nameof(source));
+            Guard.NotNull(destination, nameof(destination));
+
+            await semaphoreSlim.WaitAsync();
+
+            try
             {
                 using (var image = Image.Load(source, out var format))
                 {
@@ -123,7 +144,12 @@ namespace Squidex.Infrastructure.Assets.ImageSharp
 
                     image.Save(destination, encoder);
 
-                return Task.FromResult(GetImageInfo(image));
+                    return GetImageInfo(image);
+                }
+            }
+            finally
+            {
+                semaphoreSlim.Release();
             }
         }