Goes brute force to try to resolve: U4-4049 Some images fail when uploading multiple media files

src/Umbraco.Core/IO/FileSystemExtensions.cs

@@ -1,10 +1,42 @@
 using System;
 using System.IO;
+using System.Threading;
 
 namespace Umbraco.Core.IO
 {
     public static class FileSystemExtensions
     {
+
+        /// <summary>
+        /// Attempts to open the file at <code>filePath</code> up to <code>maxRetries</code> times,
+        /// with a thread sleep time of <code>sleepPerRetryInMilliseconds</code> between retries.
+        /// </summary>
+        public static FileStream OpenReadWithRetry(this FileInfo file, int maxRetries = 5, int sleepPerRetryInMilliseconds = 50)
+        {
+            var retries = maxRetries;
+
+            while (retries > 0)
+            {
+                try
+                {
+                    return File.OpenRead(file.FullName);
+                }
+                catch(IOException)
+                {
+                    retries--;
+
+                    if (retries == 0)
+                    {
+                        throw;
+                    }
+
+                    Thread.Sleep(sleepPerRetryInMilliseconds);
+                }
+            }
+
+            throw new ArgumentException("Retries must be greater than zero");
+        }
+
         public static long GetSize(this IFileSystem fs, string path)
         {
             using (var file = fs.OpenFile(path))

src/Umbraco.Web/Editors/MediaController.cs

@@ -32,6 +32,7 @@ using umbraco;
 using umbraco.BusinessLogic.Actions;
 using Constants = Umbraco.Core.Constants;
 using Umbraco.Core.Configuration;
+using Umbraco.Core.Persistence.FaultHandling;
 
 namespace Umbraco.Web.Editors
 {
@@ -404,7 +405,11 @@ namespace Umbraco.Web.Editors
 
                     var mediaService = ApplicationContext.Services.MediaService;
                     var f = mediaService.CreateMedia(fileName, parentId, mediaType);
-                    using (var fs = System.IO.File.OpenRead(file.LocalFileName))
+
+                    var fileInfo = new FileInfo(file.LocalFileName);
+                    var fs = fileInfo.OpenReadWithRetry();
+                    if (fs == null) throw new InvalidOperationException("Could not acquire file stream");
+                    using (fs)
                     {
                         f.SetValue(Constants.Conventions.Media.File, fileName, fs);
                     }