Added eventListener to fix unhandledRejection (#606)

Instead of rejecting the notification promise on failure, resolve with an error argument. This avoids the possibility of the promise being rejected before it is awaited.

Signed-off-by: sapthasurendran <[email protected]>

Author: sapthasurendran

fabric-network/src/impl/event/transactioneventhandler.ts

@@ -13,6 +13,7 @@ import {TransactionError} from '../../errors/transactionerror';
 
 import * as Logger from '../../logger';
 import {DefaultEventHandlerOptions} from '../../gateway';
+
 const logger = Logger.getLogger('TransactionEventHandler');
 
 export interface TxEventHandler {
@@ -43,13 +44,12 @@ export class TransactionEventHandler implements TxEventHandler {
 
 	private readonly options: DefaultEventHandlerOptions;
 	private readonly peers: Endorser[];
-	private readonly notificationPromise: Promise<void>;
+	private readonly notificationPromise: Promise<Error|undefined>;
 	private readonly unrespondedPeers: Set<Endorser>;
 	private readonly listener: CommitListener = this.eventCallback.bind(this);
 	private readonly strategySuccessCallback = this.strategySuccess.bind(this);
 	private readonly strategyFailCallback = this.strategyFail.bind(this);
-	private resolveNotificationPromise!: () => void;
-	private rejectNotificationPromise!: (reason: Error) => void;
+	private resolveNotificationPromise!: (err?: Error) => void;
 	private timeoutHandler?: NodeJS.Timeout;
 
 	/**
@@ -76,9 +76,8 @@ export class TransactionEventHandler implements TxEventHandler {
 		this.peers = strategy.getPeers();
 		this.unrespondedPeers = new Set(this.peers);
 
-		this.notificationPromise = new Promise((resolve, reject) => {
+		this.notificationPromise = new Promise((resolve) => {
 			this.resolveNotificationPromise = resolve;
-			this.rejectNotificationPromise = reject;
 		});
 	}
 
@@ -105,7 +104,10 @@ export class TransactionEventHandler implements TxEventHandler {
 	 */
 	async waitForEvents() :Promise<void> {
 		logger.debug('waitForEvents start');
-		await this.notificationPromise;
+		const err = await this.notificationPromise;
+		if (err) {
+			throw err;
+		}
 		logger.debug('waitForEvents end');
 	}
 
@@ -196,6 +198,6 @@ export class TransactionEventHandler implements TxEventHandler {
 		logger.warn('strategyFail: commit failure for transaction %j: %s', this.transactionId, error);
 
 		this.cancelListening();
-		this.rejectNotificationPromise(error);
+		this.resolveNotificationPromise(error);
 	}
 }

fabric-network/test/impl/event/transactioneventhandler.spec.ts

@@ -277,6 +277,23 @@ describe('TransactionEventHandler', () => {
 			await expect(promise).to.be.rejectedWith(/timeout/i);
 		});
 
+		it('no unhandled rejection if timeout before waitForEvents() called', async () => {
+			let unhandledRejectionErr: unknown;
+			const listener = (err:unknown) => unhandledRejectionErr = err;
+			process.on('unhandledRejection', listener);
+			try {
+				options.eventHandlerOptions = {commitTimeout: 0.01};
+				handler = new TransactionEventHandler(transactionId, network, strategy);
+				await handler.startListening();
+				await clock.runAllAsync();
+				const promise = handler.waitForEvents();
+				await expect(promise).to.be.rejectedWith(/timeout/i);
+				expect(unhandledRejectionErr).to.be.undefined;
+			} finally {
+				process.removeListener('unhandledRejection', listener);
+			}
+		});
+
 		it('does not timeout if timeout set to zero', async () => {
 			stubStrategy.eventReceived.callsArg(0);
 			options.eventHandlerOptions = {commitTimeout: 0};

test/ts-scenario/config/handlers/sample-transaction-event-handler.ts

@@ -26,9 +26,8 @@ import {Endorser} from 'fabric-common';
 class SampleTransactionEventHandler implements TxEventHandler {
 	private readonly network: Network;
 	private readonly transactionId: string;
-	private readonly notificationPromise: Promise<unknown>;
-	private resolveNotificationPromise!: (value?: unknown) => void;
-	private rejectNotificationPromise!: (reason: Error) => void;
+	private readonly notificationPromise: Promise<Error | undefined>;
+	private resolveNotificationPromise!: (err?: Error) => void;
 	private timeoutHandler?: NodeJS.Timeout;
 	private readonly listener: CommitListener = this.eventCallback.bind(this);
 	private readonly peers: Endorser[];
@@ -48,9 +47,8 @@ class SampleTransactionEventHandler implements TxEventHandler {
 		this.peers = peers;
 		this.unrespondedPeers = new Set(peers);
 
-		this.notificationPromise = new Promise((resolve, reject) => {
+		this.notificationPromise = new Promise((resolve) => {
 			this.resolveNotificationPromise = resolve;
-			this.rejectNotificationPromise = reject;
 		});
 	}
 
@@ -67,7 +65,10 @@ class SampleTransactionEventHandler implements TxEventHandler {
 	 * @throws {Error} if the transaction commit fails or is not successful within the timeout period.
 	 */
 	async waitForEvents() {
-		await this.notificationPromise;
+		const err = await this.notificationPromise;
+		if (err) {
+			throw err;
+		}
 	}
 
 	/**
@@ -103,7 +104,7 @@ class SampleTransactionEventHandler implements TxEventHandler {
 
 	private fail(error: Error) {
 		this.cancelListening();
-		this.rejectNotificationPromise(error);
+		this.resolveNotificationPromise(error);
 	}
 
 	private success() {
@@ -122,4 +123,4 @@ export const createTransactionEventHandler: TxEventHandlerFactory = (transaction
 	const mspId = network.getGateway().getIdentity().mspId;
 	const peers = network.getChannel().getEndorsers(mspId);
 	return new SampleTransactionEventHandler(transactionId, network, peers);
-};
+};