Add ability to push multiple items to a queue in a single redis round-trip

osu.Server.QueueProcessor.Tests/InputOnlyQueueTests.cs

@@ -73,6 +73,35 @@ public void SendThenReceive_Multiple()
             Assert.Equal(objects, receivedObjects);
         }
 
+        [Fact]
+        public void SendThenReceive_MultipleUsingSingleCall()
+        {
+            const int send_count = 10000;
+
+            var cts = new CancellationTokenSource(10000);
+
+            var objects = new HashSet<FakeData>();
+            for (int i = 0; i < send_count; i++)
+                objects.Add(FakeData.New());
+
+            var receivedObjects = new HashSet<FakeData>();
+
+            processor.PushToQueue(objects);
+
+            processor.Received += o =>
+            {
+                lock (receivedObjects)
+                    receivedObjects.Add(o);
+
+                if (receivedObjects.Count == send_count)
+                    cts.Cancel();
+            };
+
+            processor.Run(cts.Token);
+
+            Assert.Equal(objects, receivedObjects);
+        }
+
         /// <summary>
         /// If the processor is cancelled mid-operation, every item should either be processed or still in the queue.
         /// </summary>

osu.Server.QueueProcessor/QueueProcessor.cs

@@ -208,8 +208,19 @@ private void outputStats()
             }
         }
 
-        public void PushToQueue(T obj) =>
-            redis.GetDatabase().ListLeftPush(QueueName, JsonConvert.SerializeObject(obj));
+        /// <summary>
+        /// Push a single item to the queue.
+        /// </summary>
+        /// <param name="item"></param>
+        public void PushToQueue(T item) =>
+            redis.GetDatabase().ListLeftPush(QueueName, JsonConvert.SerializeObject(item));
+
+        /// <summary>
+        /// Push multiple items to the queue.
+        /// </summary>
+        /// <param name="items"></param>
+        public void PushToQueue(IEnumerable<T> items) =>
+            redis.GetDatabase().ListLeftPush(QueueName, items.Select(obj => new RedisValue(JsonConvert.SerializeObject(obj))).ToArray());
 
         public long GetQueueSize() =>
             redis.GetDatabase().ListLength(QueueName);