feat(batch): add async processor (#1616)

* feat(batch): add async processor

* tests: improved unit tests

* chore: removed docstring + edited test handler

packages/batch/package.json

@@ -1,6 +1,6 @@
 {
   "name": "@aws-lambda-powertools/batch",
-  "version": "1.10.0",
+  "version": "1.11.1",
   "description": "The batch processing package for the Powertools for AWS Lambda (TypeScript) library.",
   "author": {
     "name": "Amazon Web Services",
@@ -22,8 +22,7 @@
     "prepack": "node ../../.github/scripts/release_patch_package_json.js ."
   },
   "lint-staged": {
-    "*.ts": "npm run lint-fix",
-    "*.js": "npm run lint-fix"
+    "*.{js,ts}": "npm run lint-fix"
   },
   "homepage": "https://github.com/aws-powertools/powertools-lambda-typescript/tree/main/packages/batch#readme",
   "license": "MIT-0",
@@ -50,4 +49,4 @@
     "nodejs"
   ],
   "devDependencies": {}
-}
+}

packages/batch/src/AsyncBatchProcessor.ts

@@ -0,0 +1,31 @@
+import { BasePartialBatchProcessor } from './BasePartialBatchProcessor';
+import type { BaseRecord, FailureResponse, SuccessResponse } from './types';
+
+/**
+ * Process native partial responses from SQS, Kinesis Data Streams, and DynamoDB
+ */
+class AsyncBatchProcessor extends BasePartialBatchProcessor {
+  public async asyncProcessRecord(
+    record: BaseRecord
+  ): Promise<SuccessResponse | FailureResponse> {
+    try {
+      const data = this.toBatchType(record, this.eventType);
+      const result = await this.handler(data, this.options);
+
+      return this.successHandler(record, result);
+    } catch (error) {
+      return this.failureHandler(record, error as Error);
+    }
+  }
+
+  /**
+   * Process a record with instance's handler
+   * @param record Batch record to be processed
+   * @returns response of success or failure
+   */
+  public processRecord(_record: BaseRecord): SuccessResponse | FailureResponse {
+    throw new Error('Not implemented. Use asyncProcess() instead.');
+  }
+}
+
+export { AsyncBatchProcessor };

packages/batch/src/BasePartialBatchProcessor.ts

@@ -1,18 +1,20 @@
-/**
- * Process batch and partially report failed items
- */
-import { DynamoDBRecord, KinesisStreamRecord, SQSRecord } from 'aws-lambda';
-import {
-  BasePartialProcessor,
-  BatchProcessingError,
-  DATA_CLASS_MAPPING,
-  DEFAULT_RESPONSE,
+import type {
+  DynamoDBRecord,
+  KinesisStreamRecord,
+  SQSRecord,
+} from 'aws-lambda';
+import { BasePartialProcessor } from './BasePartialProcessor';
+import { DATA_CLASS_MAPPING, DEFAULT_RESPONSE, EventType } from './constants';
+import { BatchProcessingError } from './errors';
+import type {
   EventSourceDataClassTypes,
-  EventType,
-  PartialItemFailures,
   PartialItemFailureResponse,
-} from '.';
+  PartialItemFailures,
+} from './types';
 
+/**
+ * Process batch and partially report failed items
+ */
 abstract class BasePartialBatchProcessor extends BasePartialProcessor {
   public COLLECTOR_MAPPING;
 
@@ -124,13 +126,7 @@ abstract class BasePartialBatchProcessor extends BasePartialProcessor {
    * @returns true if any records resulted in exception
    */
   public hasMessagesToReport(): boolean {
-    if (this.failureMessages.length != 0) {
-      return true;
-    }
-
-    // console.debug('All ' + this.successMessages.length + ' records successfully processed');
-
-    return false;
+    return this.failureMessages.length != 0;
   }
 
   /**

packages/batch/src/BasePartialProcessor.ts

@@ -1,15 +1,15 @@
-/**
- * Abstract class for batch processors
- */
-import {
+import type {
   BaseRecord,
   BatchProcessingOptions,
   EventSourceDataClassTypes,
   FailureResponse,
   ResultType,
   SuccessResponse,
-} from '.';
+} from './types';
 
+/**
+ * Abstract class for batch processors.
+ */
 abstract class BasePartialProcessor {
   public exceptions: Error[];
 
@@ -34,6 +34,40 @@ abstract class BasePartialProcessor {
     this.handler = new Function();
   }
 
+  /**
+   * Call instance's handler for each record
+   * @returns List of processed records
+   */
+  public async asyncProcess(): Promise<(SuccessResponse | FailureResponse)[]> {
+    /**
+     * If this is an sync processor, user should have called process instead,
+     * so we call the method early to throw the error early thus failing fast.
+     */
+    if (this.constructor.name === 'BatchProcessor') {
+      await this.asyncProcessRecord(this.records[0]);
+    }
+    this.prepare();
+
+    const processingPromises: Promise<SuccessResponse | FailureResponse>[] =
+      this.records.map((record) => this.asyncProcessRecord(record));
+
+    const processedRecords: (SuccessResponse | FailureResponse)[] =
+      await Promise.all(processingPromises);
+
+    this.clean();
+
+    return processedRecords;
+  }
+
+  /**
+   * Process a record with an asyncronous handler
+   *
+   * @param record Record to be processed
+   */
+  public abstract asyncProcessRecord(
+    record: BaseRecord
+  ): Promise<SuccessResponse | FailureResponse>;
+
   /**
    * Clean class instance after processing
    */
@@ -50,7 +84,6 @@ abstract class BasePartialProcessor {
     exception: Error
   ): FailureResponse {
     const entry: FailureResponse = ['fail', exception.message, record];
-    // console.debug('Record processing exception: ' + exception.message);
     this.exceptions.push(exception);
     this.failureMessages.push(record);
 
@@ -66,12 +99,19 @@ abstract class BasePartialProcessor {
    * Call instance's handler for each record
    * @returns List of processed records
    */
-  public async process(): Promise<(SuccessResponse | FailureResponse)[]> {
+  public process(): (SuccessResponse | FailureResponse)[] {
+    /**
+     * If this is an async processor, user should have called processAsync instead,
+     * so we call the method early to throw the error early thus failing fast.
+     */
+    if (this.constructor.name === 'AsyncBatchProcessor') {
+      this.processRecord(this.records[0]);
+    }
     this.prepare();
 
     const processedRecords: (SuccessResponse | FailureResponse)[] = [];
     for (const record of this.records) {
-      processedRecords.push(await this.processRecord(record));
+      processedRecords.push(this.processRecord(record));
     }
 
     this.clean();
@@ -85,7 +125,7 @@ abstract class BasePartialProcessor {
    */
   public abstract processRecord(
     record: BaseRecord
-  ): Promise<SuccessResponse | FailureResponse>;
+  ): SuccessResponse | FailureResponse;
 
   /**
    * Set class instance attributes before execution

packages/batch/src/BatchProcessor.ts

@@ -1,30 +1,29 @@
+import { BasePartialBatchProcessor } from './BasePartialBatchProcessor';
+import type { BaseRecord, FailureResponse, SuccessResponse } from './types';
+
 /**
  * Process native partial responses from SQS, Kinesis Data Streams, and DynamoDB
  */
-import {
-  BasePartialBatchProcessor,
-  BaseRecord,
-  FailureResponse,
-  SuccessResponse,
-} from '.';
-
 class BatchProcessor extends BasePartialBatchProcessor {
+  public async asyncProcessRecord(
+    _record: BaseRecord
+  ): Promise<SuccessResponse | FailureResponse> {
+    throw new Error('Not implemented. Use process() instead.');
+  }
+
   /**
    * Process a record with instance's handler
    * @param record Batch record to be processed
    * @returns response of success or failure
    */
-  public async processRecord(
-    record: BaseRecord
-  ): Promise<SuccessResponse | FailureResponse> {
+  public processRecord(record: BaseRecord): SuccessResponse | FailureResponse {
     try {
       const data = this.toBatchType(record, this.eventType);
-
-      const result = await this.handler(data, this.options);
+      const result = this.handler(data, this.options);
 
       return this.successHandler(record, result);
-    } catch (e) {
-      return this.failureHandler(record, e as Error);
+    } catch (error) {
+      return this.failureHandler(record, error as Error);
     }
   }
 }

packages/batch/src/SqsFifoPartialProcessor.ts

@@ -1,4 +1,6 @@
-import { BatchProcessor, EventType, FailureResponse, SuccessResponse } from '.';
+import { BatchProcessor } from './BatchProcessor';
+import { EventType } from './constants';
+import type { FailureResponse, SuccessResponse } from './types';
 
 /**
  * Process native partial responses from SQS FIFO queues
@@ -14,9 +16,8 @@ class SqsFifoPartialProcessor extends BatchProcessor {
    * Call instance's handler for each record.
    * When the first failed message is detected, the process is short-circuited
    * And the remaining messages are reported as failed items
-   * TODO: change to synchronous execution if possible
    */
-  public async process(): Promise<(SuccessResponse | FailureResponse)[]> {
+  public process(): (SuccessResponse | FailureResponse)[] {
     this.prepare();
 
     const processedRecords: (SuccessResponse | FailureResponse)[] = [];
@@ -28,7 +29,7 @@ class SqsFifoPartialProcessor extends BatchProcessor {
         return this.shortCircuitProcessing(currentIndex, processedRecords);
       }
 
-      processedRecords.push(await this.processRecord(record));
+      processedRecords.push(this.processRecord(record));
       currentIndex++;
     }
 

packages/batch/src/asyncProcessPartialResponse.ts

@@ -0,0 +1,38 @@
+import { BasePartialBatchProcessor } from './BasePartialBatchProcessor';
+import { EventType } from './constants';
+import type {
+  BaseRecord,
+  BatchProcessingOptions,
+  PartialItemFailureResponse,
+} from './types';
+
+/**
+ * Higher level function to handle batch event processing
+ * @param event Lambda's original event
+ * @param recordHandler Callable function to process each record from the batch
+ * @param processor Batch processor to handle partial failure cases
+ * @returns Lambda Partial Batch Response
+ */
+const asyncProcessPartialResponse = async (
+  event: { Records: BaseRecord[] },
+  recordHandler: CallableFunction,
+  processor: BasePartialBatchProcessor,
+  options?: BatchProcessingOptions
+): Promise<PartialItemFailureResponse> => {
+  if (!event.Records) {
+    const eventTypes: string = Object.values(EventType).toString();
+    throw new Error(
+      'Failed to convert event to record batch for processing.\nPlease ensure batch event is a valid ' +
+        eventTypes +
+        ' event.'
+    );
+  }
+
+  processor.register(event.Records, recordHandler, options);
+
+  await processor.asyncProcess();
+
+  return processor.response();
+};
+
+export { asyncProcessPartialResponse };

packages/batch/src/constants.ts

@@ -1,8 +1,8 @@
-/**
- * Constants for batch processor classes
- */
 import { DynamoDBRecord, KinesisStreamRecord, SQSRecord } from 'aws-lambda';
-import type { PartialItemFailureResponse, EventSourceDataClassTypes } from '.';
+import type {
+  PartialItemFailureResponse,
+  EventSourceDataClassTypes,
+} from './types';
 
 const EventType = {
   SQS: 'SQS',

packages/batch/src/errors.ts

@@ -1,7 +1,3 @@
-/**
- * Batch processing exceptions
- */
-
 /**
  * Base error type for batch processing
  * All errors thrown by major failures extend this base class

packages/batch/src/index.ts

@@ -4,5 +4,7 @@ export * from './types';
 export * from './BasePartialProcessor';
 export * from './BasePartialBatchProcessor';
 export * from './BatchProcessor';
+export * from './AsyncBatchProcessor';
 export * from './processPartialResponse';
+export * from './asyncProcessPartialResponse';
 export * from './SqsFifoPartialProcessor';

packages/batch/src/processPartialResponse.ts

@@ -1,10 +1,10 @@
-import {
-  BasePartialBatchProcessor,
+import { BasePartialBatchProcessor } from './BasePartialBatchProcessor';
+import { EventType } from './constants';
+import type {
   BaseRecord,
   BatchProcessingOptions,
-  EventType,
   PartialItemFailureResponse,
-} from '.';
+} from './types';
 
 /**
  * Higher level function to handle batch event processing
@@ -13,12 +13,12 @@ import {
  * @param processor Batch processor to handle partial failure cases
  * @returns Lambda Partial Batch Response
  */
-const processPartialResponse = async (
+const processPartialResponse = (
   event: { Records: BaseRecord[] },
   recordHandler: CallableFunction,
   processor: BasePartialBatchProcessor,
   options?: BatchProcessingOptions
-): Promise<PartialItemFailureResponse> => {
+): PartialItemFailureResponse => {
   if (!event.Records) {
     const eventTypes: string = Object.values(EventType).toString();
     throw new Error(
@@ -30,7 +30,7 @@ const processPartialResponse = async (
 
   processor.register(event.Records, recordHandler, options);
 
-  await processor.process();
+  processor.process();
 
   return processor.response();
 };