CSHARP-2207: Large bulk writes not always splitting correctly

Author: rstam

src/MongoDB.Driver.Core/Core/Misc/SizeLimitingBatchableSourceSerializer.cs

@@ -52,8 +52,8 @@ public SizeLimitingBatchableSourceSerializer(
             _itemSerializer = Ensure.IsNotNull(itemSerializer, nameof(itemSerializer));
             _itemElementNameValidator = Ensure.IsNotNull(itemElementNameValidator, nameof(itemElementNameValidator));
             _maxBatchCount = Ensure.IsGreaterThanZero(maxBatchCount, nameof(maxBatchCount));
-            _maxItemSize = Ensure.IsBetween(maxItemSize, 1, int.MaxValue, nameof(maxItemSize));
-            _maxBatchSize = Ensure.IsBetween(maxBatchSize, maxItemSize, int.MaxValue, nameof(maxBatchSize));
+            _maxItemSize = Ensure.IsGreaterThanZero(maxItemSize, nameof(maxItemSize));
+            _maxBatchSize = Ensure.IsGreaterThanZero(maxBatchSize, nameof(maxBatchSize));
         }
 
         // public methods
@@ -88,19 +88,23 @@ public override void Serialize(BsonSerializationContext context, BsonSerializati
                     var item = value.Items[value.Offset + i];
                     _itemSerializer.Serialize(context, args, item);
 
-                    var batchSize = binaryWriter?.Position - startPosition;
-                    if (batchSize > _maxBatchSize)
+                    // always process at least one item
+                    if (i > 0)
                     {
-                        if (i > 0 && value.CanBeSplit)
+                        var batchSize = binaryWriter?.Position - startPosition;
+                        if (batchSize > _maxBatchSize)
                         {
-                            binaryWriter.BaseStream.Position = itemPosition.Value; // remove the last item
-                            binaryWriter.BaseStream.SetLength(itemPosition.Value);
-                            value.SetProcessedCount(i);
-                            return;
-                        }
-                        else
-                        {
-                            throw new ArgumentException("Batch is too large.");
+                            if (value.CanBeSplit)
+                            {
+                                binaryWriter.BaseStream.Position = itemPosition.Value; // remove the last item
+                                binaryWriter.BaseStream.SetLength(itemPosition.Value);
+                                value.SetProcessedCount(i);
+                                return;
+                            }
+                            else
+                            {
+                                throw new ArgumentException("Batch is too large.");
+                            }
                         }
                     }
                 }

src/MongoDB.Driver.Core/Core/Operations/RetryableDeleteCommandOperation.cs

@@ -123,8 +123,8 @@ private IBsonSerializer<BatchableSource<DeleteRequest>> CreateBatchSerializer(Co
             if (attempt == 1)
             {
                 var maxBatchCount = Math.Min(MaxBatchCount ?? int.MaxValue, connectionDescription.MaxBatchCount);
-                var maxItemSize = connectionDescription.MaxDocumentSize;
-                var maxBatchSize = connectionDescription.MaxWireDocumentSize;
+                var maxItemSize = connectionDescription.MaxWireDocumentSize;
+                var maxBatchSize = connectionDescription.MaxDocumentSize;
                 return new SizeLimitingBatchableSourceSerializer<DeleteRequest>(DeleteRequestSerializer.Instance, NoOpElementNameValidator.Instance, maxBatchCount, maxItemSize, maxBatchSize);
             }
             else

src/MongoDB.Driver.Core/Core/Operations/RetryableInsertCommandOperation.cs

@@ -150,7 +150,7 @@ private IBsonSerializer<BatchableSource<TDocument>> CreateBatchSerializer(Connec
             {
                 var maxBatchCount = Math.Min(MaxBatchCount ?? int.MaxValue, connectionDescription.MaxBatchCount);
                 var maxItemSize = connectionDescription.MaxDocumentSize;
-                var maxBatchSize = connectionDescription.MaxWireDocumentSize;
+                var maxBatchSize = connectionDescription.MaxDocumentSize;
                 return new SizeLimitingBatchableSourceSerializer<TDocument>(itemSerializer, elementNameValidator, maxBatchCount, maxItemSize, maxBatchSize);
             }
             else

src/MongoDB.Driver.Core/Core/Operations/RetryableUpdateCommandOperation.cs

@@ -145,7 +145,7 @@ private IBsonSerializer<BatchableSource<UpdateRequest>> CreateBatchSerializer(Co
             {
                 var maxBatchCount = Math.Min(MaxBatchCount ?? int.MaxValue, connectionDescription.MaxBatchCount);
                 var maxItemSize = connectionDescription.MaxWireDocumentSize;
-                var maxBatchSize = connectionDescription.MaxWireDocumentSize;
+                var maxBatchSize = connectionDescription.MaxDocumentSize;
                 return new SizeLimitingBatchableSourceSerializer<UpdateRequest>(UpdateRequestSerializer.Instance, NoOpElementNameValidator.Instance, maxBatchCount, maxItemSize, maxBatchSize);
             }
             else

tests/MongoDB.Driver.Core.TestHelpers/EventCapturer.cs

@@ -15,6 +15,7 @@
 
 using System;
 using System.Collections.Generic;
+using System.Linq;
 using MongoDB.Bson;
 using MongoDB.Driver.Core.Events;
 using MongoDB.Driver.Core.Misc;
@@ -64,6 +65,17 @@ public void Clear()
             }
         }
 
+        public List<object> Events
+        {
+            get
+            {
+                lock (_lock)
+                {
+                    return _capturedEvents.ToList();
+                }
+            }
+        }
+
         public object Next()
         {
             lock (_lock)