Add noise retry option

Fixes #1690

Author: szmarczak

source/core/calculate-retry-delay.ts

@@ -39,7 +39,7 @@ const calculateRetryDelay: Returns<RetryFunction, number> = ({
 		}
 	}
 
-	const noise = Math.random() * 100;
+	const noise = Math.random() * retryOptions.noise;
 	return Math.min(((2 ** (attemptCount - 1)) * 1000), retryOptions.backoffLimit) + noise;
 };
 

source/core/options.ts

@@ -295,6 +295,7 @@ export interface RetryOptions {
 	errorCodes: string[];
 	calculateDelay: RetryFunction;
 	backoffLimit: number;
+	noise: number;
 	maxRetryAfter?: number;
 }
 
@@ -618,7 +619,8 @@ const defaultInternals: Options['_internals'] = {
 		],
 		maxRetryAfter: undefined,
 		calculateDelay: ({computedValue}) => computedValue,
-		backoffLimit: Number.POSITIVE_INFINITY
+		backoffLimit: Number.POSITIVE_INFINITY,
+		noise: 100
 	},
 	localAddress: undefined,
 	method: 'GET',
@@ -1785,6 +1787,11 @@ export default class Options {
 		assert.any([is.array, is.undefined], value.methods);
 		assert.any([is.array, is.undefined], value.statusCodes);
 		assert.any([is.array, is.undefined], value.errorCodes);
+		assert.any([is.number, is.undefined], value.noise);
+
+		if (value.noise && Math.abs(value.noise) > 100) {
+			throw new Error(`The maximum acceptable retry noise is +/- 100ms, got ${value.noise}`);
+		}
 
 		for (const key in value) {
 			if (!(key in this._internals.retry)) {

test/arguments.ts

@@ -557,3 +557,53 @@ test('prefixUrl is properly replaced when extending', withServer, async (t, serv
 
 	t.is(await child.get('').text(), '/other/path/');
 });
+
+test('throws on too large noise', t => {
+	t.throws(() => {
+		new Options({
+			retry: {
+				noise: 101
+			}
+		});
+	}, {
+		message: 'The maximum acceptable retry noise is +/- 100ms, got 101'
+	});
+
+	t.throws(() => {
+		new Options({
+			retry: {
+				noise: -101
+			}
+		});
+	}, {
+		message: 'The maximum acceptable retry noise is +/- 100ms, got -101'
+	});
+
+	t.throws(() => {
+		new Options({
+			retry: {
+				noise: Number.POSITIVE_INFINITY
+			}
+		});
+	}, {
+		message: 'The maximum acceptable retry noise is +/- 100ms, got Infinity'
+	});
+
+	t.throws(() => {
+		new Options({
+			retry: {
+				noise: Number.NEGATIVE_INFINITY
+			}
+		});
+	}, {
+		message: 'The maximum acceptable retry noise is +/- 100ms, got -Infinity'
+	});
+
+	t.notThrows(() => {
+		new Options({
+			retry: {
+				noise: 0
+			}
+		});
+	});
+});