shuffle cdn shard configs to allow for multiple file shards to handle one file, randomly distributing

MareSynchronosServer/MareSynchronosServer/Hubs/MareHub.Files.cs

@@ -59,6 +59,7 @@ public partial class MareHub
         {
             var forbiddenFile = forbiddenFiles.SingleOrDefault(f => string.Equals(f.Hash, file.Hash, StringComparison.OrdinalIgnoreCase));
 
+            shardConfig.Shuffle();
             var matchedShardConfig = shardConfig.Find(f => f.FileMatchRegex.Match(file.Hash).Success);
             var baseUrl = matchedShardConfig?.CdnFullUrl ?? _mainCdnFullUrl;
 

MareSynchronosServer/MareSynchronosShared/Utils/StringUtils.cs

@@ -29,3 +29,21 @@ public static class StringUtils
         return BitConverter.ToString(sha256.ComputeHash(Encoding.UTF8.GetBytes(input))).Replace("-", "", StringComparison.OrdinalIgnoreCase);
     }
 }
+
+public static class ListUtils
+{
+    private static Random rng = new();
+
+    public static void Shuffle<T>(this IList<T> list)
+    {
+        int n = list.Count;
+        while (n > 1)
+        {
+            n--;
+            int k = rng.Next(n + 1);
+            T value = list[k];
+            list[k] = list[n];
+            list[n] = value;
+        }
+    }
+}