feat(NODE-6337): implement client bulk write batching

src/cmap/commands.ts

@@ -429,10 +429,66 @@ export interface OpMsgOptions {
 
 /** @internal */
 export class DocumentSequence {
+  field: string;
   documents: Document[];
+  serializedDocumentsLength: number;
+  private chunks: Uint8Array[];
+  private header?: Buffer;
 
-  constructor(documents: Document[]) {
-    this.documents = documents;
+  /**
+   * Create a new document sequence for the provided field.
+   * @param field - The field it will replace.
+   */
+  constructor(field: string, documents?: Document[]) {
+    this.field = field;
+    this.documents = [];
+    this.chunks = [];
+    this.serializedDocumentsLength = 0;
+    this.init();
+    if (documents) {
+      for (const doc of documents) {
+        this.push(doc, BSON.serialize(doc));
+      }
+    }
+  }
+
+  /**
+   * Initialize the buffer chunks.
+   */
+  private init() {
+    // Document sequences starts with type 1 at the first byte.
+    const buffer = Buffer.allocUnsafe(1 + 4 + this.field.length + 1);
+    buffer[0] = 1;
+    // Third part is the field name at offset 5 with trailing null byte.
+    encodeUTF8Into(buffer, `${this.field}\0`, 5);
+    this.chunks.push(buffer);
+    this.header = buffer;
+  }
+
+  /**
+   * Push a document to the document sequence. Will serialize the document
+   * as well and return the current serialized length of all documents.
+   * @param document - The document to add.
+   * @param buffer - The serialized document in raw BSON.
+   * @returns The new totoal document sequence length.
+   */
+  push(document: Document, buffer: Uint8Array): number {
+    this.serializedDocumentsLength += buffer.length;
+    // Push the document.
+    this.documents.push(document);
+    // Push the document raw bson.
+    this.chunks.push(buffer);
+    // Write the new length.
+    this.header?.writeInt32LE(4 + this.field.length + 1 + this.serializedDocumentsLength, 1);
+    return this.serializedDocumentsLength + (this.header?.length ?? 0);
+  }
+
+  /**
+   * Get the fully serialized bytes for the document sequence section.
+   * @returns The section bytes.
+   */
+  toBin(): Uint8Array {
+    return Buffer.concat(this.chunks);
   }
 }
 
@@ -543,21 +599,7 @@ export class OpMsgRequest {
     const chunks = [];
     for (const [key, value] of Object.entries(document)) {
       if (value instanceof DocumentSequence) {
-        // Document sequences starts with type 1 at the first byte.
-        const buffer = Buffer.allocUnsafe(1 + 4 + key.length + 1);
-        buffer[0] = 1;
-        // Third part is the field name at offset 5 with trailing null byte.
-        encodeUTF8Into(buffer, `${key}\0`, 5);
-        chunks.push(buffer);
-        // Fourth part are the documents' bytes.
-        let docsLength = 0;
-        for (const doc of value.documents) {
-          const docBson = this.serializeBson(doc);
-          docsLength += docBson.length;
-          chunks.push(docBson);
-        }
-        // Second part of the sequence is the length at offset 1;
-        buffer.writeInt32LE(4 + key.length + 1 + docsLength, 1);
+        chunks.push(value.toBin());
         // Why are we removing the field from the command? This is because it needs to be
         // removed in the OP_MSG request first section, and DocumentSequence is not a
         // BSON type and is specific to the MongoDB wire protocol so there's nothing

src/cursor/client_bulk_write_cursor.ts

@@ -1,6 +1,6 @@
 import type { Document } from '../bson';
 import { type ClientBulkWriteCursorResponse } from '../cmap/wire_protocol/responses';
-import { MongoBulkWriteCursorError } from '../error';
+import { MongoClientBulkWriteCursorError } from '../error';
 import type { MongoClient } from '../mongo_client';
 import { ClientBulkWriteOperation } from '../operations/client_bulk_write/client_bulk_write';
 import { type ClientBulkWriteOptions } from '../operations/client_bulk_write/common';
@@ -44,7 +44,7 @@ export class ClientBulkWriteCursor extends AbstractCursor {
    */
   get response(): ClientBulkWriteCursorResponse {
     if (this.cursorResponse) return this.cursorResponse;
-    throw new MongoBulkWriteCursorError(
+    throw new MongoClientBulkWriteCursorError(
       'No client bulk write cursor response returned from the server.'
     );
   }

src/error.ts

@@ -622,7 +622,7 @@ export class MongoGCPError extends MongoOIDCError {
  * @public
  * @category Error
  */
-export class MongoBulkWriteCursorError extends MongoRuntimeError {
+export class MongoClientBulkWriteCursorError extends MongoRuntimeError {
   /**
    * **Do not use this constructor!**
    *
@@ -639,7 +639,34 @@ export class MongoBulkWriteCursorError extends MongoRuntimeError {
   }
 
   override get name(): string {
-    return 'MongoBulkWriteCursorError';
+    return 'MongoClientBulkWriteCursorError';
+  }
+}
+
+/**
+ * An error indicating that an error occurred on the client when executing a client bulk write.
+ *
+ * @public
+ * @category Error
+ */
+export class MongoClientBulkWriteExecutionError extends MongoRuntimeError {
+  /**
+   * **Do not use this constructor!**
+   *
+   * Meant for internal use only.
+   *
+   * @remarks
+   * This class is only meant to be constructed within the driver. This constructor is
+   * not subject to semantic versioning compatibility guarantees and may change at any time.
+   *
+   * @public
+   **/
+  constructor(message: string) {
+    super(message);
+  }
+
+  override get name(): string {
+    return 'MongoClientBulkWriteExecutionError';
   }
 }
 

src/index.ts

@@ -44,8 +44,9 @@ export {
   MongoAWSError,
   MongoAzureError,
   MongoBatchReExecutionError,
-  MongoBulkWriteCursorError,
   MongoChangeStreamError,
+  MongoClientBulkWriteCursorError,
+  MongoClientBulkWriteExecutionError,
   MongoCompatibilityError,
   MongoCursorExhaustedError,
   MongoCursorInUseError,

src/operations/client_bulk_write/command_builder.ts

@@ -1,4 +1,4 @@
-import { type Document } from '../../bson';
+import { BSON, type Document } from '../../bson';
 import { DocumentSequence } from '../../cmap/commands';
 import { type PkFactory } from '../../mongo_client';
 import type { Filter, OptionalId, UpdateFilter, WithoutId } from '../../mongo_types';
@@ -28,6 +28,11 @@ export interface ClientBulkWriteCommand {
   comment?: any;
 }
 
+/**
+ * The bytes overhead for the extra fields added post command generation.
+ */
+const MESSAGE_OVERHEAD_BYTES = 1000;
+
 /** @internal */
 export class ClientBulkWriteCommandBuilder {
   models: AnyClientBulkWriteModel[];
@@ -62,32 +67,148 @@ export class ClientBulkWriteCommandBuilder {
   /**
    * Build the bulk write commands from the models.
    */
-  buildCommands(): ClientBulkWriteCommand[] {
+  buildCommands(maxMessageSizeBytes: number, maxWriteBatchSize: number): ClientBulkWriteCommand[] {
     // Iterate the models to build the ops and nsInfo fields.
-    const operations = [];
+    // We need to do this in a loop which creates one command each up
+    // to the max bson size or max message size.
+    const commands: ClientBulkWriteCommand[] = [];
+    let currentCommandLength = 0;
     let currentNamespaceIndex = 0;
+    let currentCommand: ClientBulkWriteCommand = this.baseCommand();
     const namespaces = new Map<string, number>();
+
     for (const model of this.models) {
       const ns = model.namespace;
       const index = namespaces.get(ns);
+
+      /**
+       * Convenience function for resetting everything when a new batch
+       * is started.
+       */
+      const reset = () => {
+        commands.push(currentCommand);
+        namespaces.clear();
+        currentNamespaceIndex = 0;
+        currentCommand = this.baseCommand();
+        namespaces.set(ns, currentNamespaceIndex);
+      };
+
       if (index != null) {
-        operations.push(buildOperation(model, index, this.pkFactory));
+        // Pushing to the ops document sequence returns the bytes length added.
+        const operation = buildOperation(model, index, this.pkFactory);
+        const operationBuffer = BSON.serialize(operation);
+
+        // Check if the operation buffer can fit in the current command. If it can,
+        // then add the operation to the document sequence and increment the
+        // current length as long as the ops don't exceed the maxWriteBatchSize.
+        if (
+          currentCommandLength + operationBuffer.length < maxMessageSizeBytes &&
+          currentCommand.ops.documents.length < maxWriteBatchSize
+        ) {
+          // Pushing to the ops document sequence returns the bytes length added.
+          currentCommandLength =
+            MESSAGE_OVERHEAD_BYTES + this.addOperation(currentCommand, operation, operationBuffer);
+        } else {
+          // We need to batch. Push the current command to the commands
+          // array and create a new current command. We aslo need to clear the namespaces
+          // map for the new command.
+          reset();
+
+          const nsInfo = { ns: ns };
+          const nsInfoBuffer = BSON.serialize(nsInfo);
+          currentCommandLength =
+            MESSAGE_OVERHEAD_BYTES +
+            this.addOperationAndNsInfo(
+              currentCommand,
+              operation,
+              operationBuffer,
+              nsInfo,
+              nsInfoBuffer
+            );
+        }
       } else {
         namespaces.set(ns, currentNamespaceIndex);
-        operations.push(buildOperation(model, currentNamespaceIndex, this.pkFactory));
+        const nsInfo = { ns: ns };
+        const nsInfoBuffer = BSON.serialize(nsInfo);
+        const operation = buildOperation(model, currentNamespaceIndex, this.pkFactory);
+        const operationBuffer = BSON.serialize(operation);
+
+        // Check if the operation and nsInfo buffers can fit in the command. If they
+        // can, then add the operation and nsInfo to their respective document
+        // sequences and increment the current length as long as the ops don't exceed
+        // the maxWriteBatchSize.
+        if (
+          currentCommandLength + nsInfoBuffer.length + operationBuffer.length <
+            maxMessageSizeBytes &&
+          currentCommand.ops.documents.length < maxWriteBatchSize
+        ) {
+          currentCommandLength =
+            MESSAGE_OVERHEAD_BYTES +
+            this.addOperationAndNsInfo(
+              currentCommand,
+              operation,
+              operationBuffer,
+              nsInfo,
+              nsInfoBuffer
+            );
+        } else {
+          // We need to batch. Push the current command to the commands
+          // array and create a new current command. Aslo clear the namespaces map.
+          reset();
+
+          currentCommandLength =
+            MESSAGE_OVERHEAD_BYTES +
+            this.addOperationAndNsInfo(
+              currentCommand,
+              operation,
+              operationBuffer,
+              nsInfo,
+              nsInfoBuffer
+            );
+        }
+        // We've added a new namespace, increment the namespace index.
         currentNamespaceIndex++;
       }
     }
 
-    const nsInfo = Array.from(namespaces.keys(), ns => ({ ns }));
+    // After we've finisihed iterating all the models put the last current command
+    // only if there are operations in it.
+    if (currentCommand.ops.documents.length > 0) {
+      commands.push(currentCommand);
+    }
 
-    // The base command.
+    return commands;
+  }
+
+  private addOperation(
+    command: ClientBulkWriteCommand,
+    operation: Document,
+    operationBuffer: Uint8Array
+  ): number {
+    // Pushing to the ops document sequence returns the bytes length added.
+    return command.ops.push(operation, operationBuffer);
+  }
+
+  private addOperationAndNsInfo(
+    command: ClientBulkWriteCommand,
+    operation: Document,
+    operationBuffer: Uint8Array,
+    nsInfo: Document,
+    nsInfoBuffer: Uint8Array
+  ): number {
+    // Pushing to the nsInfo document sequence returns the bytes length added.
+    const nsInfoLength = command.nsInfo.push(nsInfo, nsInfoBuffer);
+    const opsLength = this.addOperation(command, operation, operationBuffer);
+    return nsInfoLength + opsLength;
+  }
+
+  private baseCommand(): ClientBulkWriteCommand {
     const command: ClientBulkWriteCommand = {
       bulkWrite: 1,
       errorsOnly: this.errorsOnly,
       ordered: this.options.ordered ?? true,
-      ops: new DocumentSequence(operations),
-      nsInfo: new DocumentSequence(nsInfo)
+      ops: new DocumentSequence('ops'),
+      nsInfo: new DocumentSequence('nsInfo')
     };
     // Add bypassDocumentValidation if it was present in the options.
     if (this.options.bypassDocumentValidation != null) {
@@ -103,7 +224,8 @@ export class ClientBulkWriteCommandBuilder {
     if (this.options.comment !== undefined) {
       command.comment = this.options.comment;
     }
-    return [command];
+
+    return command;
   }
 }