Fallback to ArrayPool in Kestrel (#52106)

Author: BrennanConroy

src/Servers/Kestrel/Core/src/Internal/Http/Http1OutputProducer.cs

@@ -740,6 +740,14 @@ private void AddSegment(int sizeHint = 0)
             _currentSegment = owner.Memory;
             _currentSegmentOwner = owner;
         }
+        else if (sizeHint <= MemoryPool<byte>.Shared.MaxBufferSize)
+        {
+            // fallback to ArrayPool instead of the passed in memory pool (default is PinnedBlockMemoryPool)
+            // PinnedBlockMemoryPool currently defaults to a low (4k) max buffer size while ArrayPool is 2G
+            var owner = MemoryPool<byte>.Shared.Rent(sizeHint);
+            _currentSegment = owner.Memory;
+            _currentSegmentOwner = owner;
+        }
         else
         {
             _currentSegment = new byte[sizeHint];

src/Servers/Kestrel/test/InMemory.FunctionalTests/ChunkedResponseTests.cs

@@ -1042,7 +1042,7 @@ public async Task GetMemoryWithSizeHintWithoutStartAsync()
             Assert.Equal(4096, memory.Length);
 
             memory = response.BodyWriter.GetMemory(1000000);
-            Assert.Equal(1000000, memory.Length);
+            Assert.True(memory.Length >= 1000000);
             await Task.CompletedTask;
         }, testContext))
         {